Prevalence and Clinical Correlates of Antinuclear Antibody (ANA) in Patients with Gastroparesis

Abstract

Background:

Autoimmunity may play a role in the pathogenesis of gastroparesis in a subset of patients. Antinuclear antibody (ANA) testing is often used to screen for autoimmune disorders.

Aims:

1) Determine prevalence of a positive ANA in patients with gastroparesis; 2) Describe characteristics of idiopathic gastroparesis patients with positive ANA.

Methods:

Patients were assessed with gastric emptying scintigraphy (GES), symptom assessment via Patient Assessment of Upper GI Symptoms [PAGI-SYM], and blood tests - ANA, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP).

Results:

Positive ANA was seen in 148 of 893 (17%) patients with gastroparesis; being similar in idiopathic (16% of 536 patients), T1DM (16% of 162), T2DM (18% of 147), and postfundoplication (19% of 48 patients) gastroparesis. Among 536 patients with idiopathic gastroparesis, ANA titer 1:40-1:80 was seen in 33 (6%) patients, 1:160-1:320 in 36 (7%) patients, and ≥1:640 in 17 (3%) patients. Increasing ANA titer was associated with female gender (p=0.05), Hispanic ethnicity (p=0.02), comorbid rheumatoid arthritis (p=0.02), systemic sclerosis (p=0.004), and elevated ESR (p=0.007). ANA positivity was associated with lower total GCSI (p=0.007) and lower nausea/vomiting subscale (p=0.0005), but not related to gastric emptying.

Conclusions:

The prevalence of a positive ANA in patients with gastroparesis was high at ~17%, and did not differ significantly based on etiology. In idiopathic patients, ANA positivity was associated with rheumatoid arthritis, systemic sclerosis, and elevated ESR. ANA-positive gastroparesis represents a subset who often have other autoimmune symptoms or disorders, but less severe nausea and vomiting.

Introduction

Autoimmunity may play a role in the pathogenesis of gastroparesis in a subset of patients (1). The antinuclear antibody (ANA) test is used to screen for autoimmune rheumatic disorders (AIRDs), such as systemic lupus erythematosus (SLE), systemic sclerosis (SSc) and Sjogren’s syndrome (2). It can also be positive in autoimmune thyroid conditions such as Hashimoto’s and Graves’s associated with hypo and hyper-function of the thyroid, respectively.

Gastroparesis can be a feature of many AIRDs, particularly SSc-spectrum diseases which most commonly include SSc and mixed connective tissue disease (3). SLE and Sjogren’s are also among the rare causes of gastroparesis (4,5). In SSc, gastrointestinal symptoms are varied and can involve any part of the GI tract; but esophageal dysmotility, intestinal pseudo-obstruction and constipation are most often described (6).

The ANA test is often obtained during the diagnostic work up in patients with gastroparesis (7). However, the significance and clinical utility of this test in patients with gastroparesis remain unclear. How the ANA might aid in the understanding of patients with gastroparesis, in terms of symptoms, test results, comorbidities, and outcomes is the subject of this report. The specific aims of this study were to: 1) Determine the prevalence of a positive ANA among patients with gastroparesis; 2) Describe the characteristics of idiopathic gastroparesis patients with positive ANA; 3) Compare symptoms, transit delay, and outcomes in ANA positive vs ANA negative gastroparesis patients, and 4) Determine if ANA positive idiopathic gastroparesis have worse prognosis at 1 year follow up compared to ANA negative gastroparesis patients.

Methods

Overview

For enrollment into the NIDDK Gastroparesis Registries, patients with symptoms of gastroparesis are assessed with ANA, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), autoimmune comorbidities, gastric emptying scintigraphy (GES), wireless motility capsule (WMC) assessing segmental gut transit, and symptom assessment via Patient Assessment of Upper GI Symptoms [PAGI-SYM] including the Gastroparesis Cardinal Symptom Index (GCSI). We also ascertain the presence of known history of established autoimmune disorders (SLE, scleroderma, rheumatoid arthritis) per patient report. The study was approved by the Institutional Review Board at each center. All authors had access to study data and reviewed and approved the final manuscript.

Patients

The NIDDK Gastroparesis Clinical Research Consortium (GpCRC) is a network of seven clinical centers and Scientific Data Research Center. Patients were enrolled in NIDDK Gastroparesis Registry, Gastroparesis Registry 2, and Gastroparesis Registry 3 (ClinicalTrials.gov Identifier: NCT01696747) which are observational studies of patients with gastroparesis (8) with entry criteria being 18 years or older with symptoms of at least 12 weeks, gastric emptying scintigraphy (GES) within 6 months of enrollment, and no structural abnormality as seen by upper endoscopy within one year of enrollment. Patients were recruited into the registry based on the presence of their symptoms of gastroparesis. We did not systematically include patients with underlying autoimmune conditions, like SLE or SSc. The patients enrolled in the registry were further stratified as having either idiopathic, diabetic, or postfundoplication gastroparesis. Diabetes was based by patient report, physician diagnosis, and HgbA1c ≥6.5%. Gastroparesis was labeled idiopathic in the absence of previous gastric surgery, diabetes history, or other known etiologies. At each study visit (enrollment, 6 months, and 12 months), symptoms and treatments were assessed, and questionnaires were filled out. Patients received standard of care evaluations and treatments during follow-up, allowing adjustments or additions of treatments for their clinical care. Repeat PAGI-SYM was administered to patients at 24 and 48 weeks of follow-up.

Study Protocol

Patients completed case report forms including data on gastroparesis disease onset, symptoms, body weight, disease profile, associated medical conditions including diabetes, and medication and supplemental therapies. Prior surgeries were inquired. We also asked about the presence of known autoimmune disorders including SLE, SSc, rheumatoid arthritis as well as presence of Raynaud’s phenomenon.

The clinical severity of gastroparesis was ranked as grade 1: mild gastroparesis (mild symptoms relatively controlled); grade 2: compensated gastroparesis (symptoms only partially controlled with medications); grade 3: refractory gastroparesis (refractory symptoms that are not controlled) (9).

Each patient filled out the Patient Assessment of Upper GI Symptoms (PAGI-SYM) questionnaire which assesses symptoms of gastroparesis, dyspepsia, and gastroesophageal reflux disease (10); it includes the nine symptoms of the Gastroparesis Cardinal Symptom Index (GCSI) (11). Patients were asked to assess the severity of their symptoms during the previous two weeks from 0 to 5 where no symptoms=0, very mild=1, mild=2, moderate=3, severe=4, and very severe=5.

Quality of life was assessed with two validated instruments. The Medical Outcomes Study 36-Item Short-Form Health Survey version 2 (SF-36v2) was used to assess the patients’ overall physical and mental health (12). Disease-specific quality of life was assessed by Patient Assessment of Upper Gastrointestinal Disorders Quality of Life (PAGI-QOL) survey, which scores 30 factors from 0 (none of the time) to 5 (all of the time) (13). Patients were asked how often their gastrointestinal problems have affected different aspects of their quality of life and well-being in the past two weeks.

Psychological functioning was assessed using Beck Depression Inventory (BDI) and State-Trait Anxiety Inventory (STAI). The BDI is a 21-question inventory assessing depression, cognition, and physical well-being (14). Each answer is scored on a scale of 0 to 3. Higher total scores indicate more severe depressive symptoms. The STAI consists of 20 questions relating to state anxiety (a temporary or emotional state) and 20 questions pertaining to trait anxiety (long standing personality trait anxiety with a general propensity to be anxious) (15).

Gastric Emptying Scintigraphy

Patients stopped medications that could affect gastrointestinal motility for 72 hours prior to the study and reported in the morning after fasting overnight. Diabetic patients had glucose checked to ensure <275 mg/dl. Gastric emptying scintigraphy was performed using standard low-fat, Eggbeaters^® meal to measure solid food emptying over 4 hours (16,17). Gastric retention of Tc-99m >60 % at 2 hours and/or >10% at 4 hours was considered delayed gastric emptying.

Wireless Motility Capsule (WMC)

For WMC testing (18,19), patients stopped proton pump inhibitors for 7 days, and histamine₂-receptor antagonists, prokinetics, opiates, anticholinergics, cannabinoids, isotonic polyethylene glycol electrolyte preparations, and laxatives for 3 days. On the evening before testing, insulin-requiring diabetics injected half of their usual long-acting insulin dose. Patients fasted overnight before testing. Glucose measurements were obtained in diabetic patients to ensure fasting glucose <275 mg/dL. Patients ingested one SmartBar^® (Medtronic) (255 kcal, 66% carbohydrate, 17% protein, 2% fat, 3% fiber) over 10 minutes with 50 mL water. The WMC was swallowed with 50 mL of water. Patients did not eat for 6 hours after WMC ingestion, and then resumed their normal diet. They returned for evaluation in 4–7 days. Gastric emptying times (GET) were calculated from WMC ingestion to when the capsule passed into the duodenum (abrupt ≥2 pH unit increase to levels ≥4). Small bowel transit times (SBTT) were calculated from end of GET period to ileocecal junction passage (pH decreased ≥1.0 pH unit for at least 10 minutes ≥30 minutes after pyloric passage). WMC evacuation was detected by abrupt decrease in temperature. Colon transit times (CTT) were calculated from end of SBTT period to time of anal capsule expulsion. Normal gastrointestinal transit included gastric emptying times (GET) ≤5 hours, small bowel transit times (SBTT) ≤6 hours, and colon transit times (CTT) ≤59 hours (18).

Blood tests

Laboratory measures included complete blood count (CBC), ANA (positivity and titer) by the immunofluorescence assay (IFA), hemoglobin A1_C, and inflammatory markers (ESR, high sensitivity CRP). These tests were performed at the respective institutional laboratories.

Statistical Methods

Baseline patient characteristics were first compared by etiology of gastroparesis then by positivity of the ANA, then by increasing titer ANA positivity. Data are presented as means±SD or N (%) and p-values determined for categorical covariates by Fisher’s exact test for binary categorization of ANA or Cochran’s chi-square test for trend for ordinal categorization of ANA and for continuous covariates by t-test for binary categorization of ANA or linear regression with ordinal categorization of ANA. Multiple linear regression analyses used Akaike Information Criteria (AIC) to determine a reduced set of covariates from a candidate set including all baseline covariates (20). All p-values are two-sided and not corrected for multiple comparisons since these are exploratory analyses. Analyses were conducted using SAS 9.4 (21) and Stata 15.1 (22).

Results

A positive ANA test was seen in 148 of 893 (17%) patients with gastroparesis (Table 1); being equally distributed among idiopathic (16% of 536 patients), T1DM (16% of 162), T2DM (18% of 147), and postfundoplication (19% of 48 patients) etiologies of gastroparesis (p=0.89).

Table 1.

Clinical and laboratory characteristics at enrollment by etiology in patients with delayed gastric emptying

	Etiology
Covariate	Idiopathic (n=536)	T1DM (n=162)	T2DM (n=147)	Post fundo plication (n=48)	Total (n=893)	P-value
	Mean (SD) / n (%)	Mean (SD) / n (%)	Mean (SD) / n (%)	Mean (SD) / n (%)	Mean (SD) / n (%)
ANA positive	86 (16%)	26 (16%)	27 (18%)	9 (19%)	148 (17%)	0.89
ANA Result						0.81
Negative	450 (84%)	136 (84%)	120 (82%)	39 (81%)	745 (83%)
1:40-1:80	33 (6%)	7 (4%)	6 (4%)	2 (4%)	48 (5%)
1:160-1:320	36 (7%)	12 (7%)	12 (8%)	5 (10%)	65 (7%)
>1:640	17 (3%)	7 (4%)	9 (6%)	2 (4%)	35 (4%)
Demographics
White race	496 (93%)	133 (82%)	120 (82%)	43 (90%)	792 (89%)	<0.0001
Female	476 (89%)	115 (71%)	117 (80%)	37 (77%)	745 (83%)	<0.0001
Hispanic	46 (9%)	45 (28%)	33 (22%)	3 (6%)	127 (14%)	<0.0001
Age - yrs	40 (14)	42 (12)	51 (12)	55 (15)	43 (14)	<0.0001
Married	291 (54%)	87 (54%)	85 (58%)	31 (65%)	494 (55%)	0.49
BMI –kg/m2	26 (7)	28 (6)	32 (7)	27 (7)	27 (7)	<0.0001
Comorbidities
Arthritis	28 (6%)	3 (2%)	13 (10%)	5 (12%)	49 (6%)	0.03
Scleroderma	9 (2%)	1 (1%)	2 (1%)	0 (0%)	12 (1%)	0.63
SLE*	9/452	3/141	0/131	2/42	14/766	0.20
Collagen*	1/452	0/141	0/131	0/42	1/766	0.87
Raynaud†	27/291	1/86	3/91	2/31	33/499	0.03
Other autoimmune*	22/452	3/141	3/131	2/42	30/766	0.35
GES
1 hr - %	81 (13)	85 (13)	82 (14)	83 (15)	82 (14)	0.01
2 hr - %	64 (16)	71 (19(	67 (20)	70 (18)	66 (18)	<0.0001
4 hr - %	28 (18)	46 (26)	37 (24)	44 (25)	33 (23)	<0.0001
Labs
CRP – mg/dL	0.9 (1.7)	1.2 (1.9)	1.1 (1.7)	0.8 (1.1)	1.0 (1.7)	0.23
ESR – mm/hr	15 (15)	32 (27)	27 (22)	16 (14)	20 (20)	<0.0001
HbA1c - %	5.3 (0.5)	8.5 (2.0)	7.7 (1.9)	5.6 (0.5)	6.3 (1.8)	<0.0001

^*Not available in GpR1

^†Not available in GpR1 or GpR3

Characteristics at enrollment by ANA positivity in idiopathic patients with delayed gastric emptying are shown in Table 2. Of the 536 patients with idiopathic gastroparesis, 86 had a positive ANA whereas 450 had a negative ANA. Positive ANA was associated with elevated ESR (p=0.03), presence of Raynaud’s phenomenon (p=0.04), and development of SSc (p=0.04). ANA positivity was also associated with lower severity of nausea, retching, and vomiting with a decrease in nausea/vomiting subscore and a decreased total GCSI in comparison to those with negative ANA. ANA positivity was associated with a higher PAGI-QOL (p=0.05), and trend for increase SF36 physical (p=0.08) and SF36 mental (p=0.07).

Table 2.

Characteristics at enrollment by ANA positivity in idiopathic patients with delayed gastric emptying

	ANA status
	Negative (n=450)	Positive (n=86)	P-value
	Mean (SD) / n (%)	Mean (SD) / n (%)
Demographics
White race	418 (93%)	78 (91%)	0.50
Female	395 (88%)	81 (94%)	0.09
Hispanic	37 (8%)	9 (10%)	0.53
Age - yrs	40 (14)	42 (13)	0.31
Married	243 (54%)	48 (56%)	0.81
BMI – kg/m2	26 (7)	26 (7)	0.85
Gp characteristics
Acute onset	195 (43%)	39 (45%)	0.81
Grade			0.16
1	71 (16%)	20 (24%)
2	292 (65%)	54 (64%)
3	84 (19%)	11 (13%)
Pattern			0.14
Chronic, stable	106 (24%)	18 (21%)
Chronic, worse	132 (29%)	16 (19%)
Chronic, improve	20 (4%)	6 (7%)
Chronic, periodic	129 (29%)	33 (38%)
Cyclic	61 (13%)	13 (15%)
Comorbidities
Arthritis	23 (5%)	9 (10%)	0.08
Scleroderma	5 (1%)	4 (5%)	0.04
SLE*	7/370 (2%)	2/82 (2%)	0.67
Collagen Vascular Disorder*	0/370 (0%)	1/82 (1%)	0.18
Raynaud’s phenomena†	17/230 (7%)	10/61 (16%)	0.04
Other autoimmune disorder*	16/370 (4%)	6/82 (7%)	0.26
GES
1 hr - %	81 (13)	81 (15)	0.88
2 hr - %	64 (16)	66 (17)	0.39
4 hr - %	28 (19)	28 (17)	0.87
Labs
CRP – mg/dL	0.9 (1.7)	0.9 (2.0)	0.93
CRP >10 mg/dL	3 (1%)	1 (1%)	0.50
ESR – mm/hr	14 (14)	18 (16)	0.03
ESR >22 mm/hr if male; >29 mm/hr if female	57 (13%)	19 (22%)	0.03
HbA1c - %	5.4 (0.5)	5.3 (0.5)	0.12
PAGI-SYM
GCSI
Nausea	3.4 (1.4)	3.1 (1.6)	0.06
Retching	1.8 (1.7)	1.2 (1.5)	0.005
Vomiting	1.8 (1.9)	1.2 (1.7)	0.007
Nausea subscale	2.4 (1.4)	1.9 (1.3)	0.003
Stomach fullness	3.7 (1.2)	3.6 (1.2)	0.33
Unable to finish meal	3.6 (1.4)	3.3 (1.6)	0.13
Felt full after meal	3.7 (1.3)	3.6 (1.4)	0.34
Loss of appetite	3.0 (1.5)	2.7 (1.6)	0.06
Fullness subscale	3.5 (1.1)	3.3 (1.2)	0.10
Bloating	3.3 (1.6)	3.3 (1.5)	0.85
Stomach visibly larger	3.0 (1.7)	2.8 (1.7)	0.29
Bloating subscale	3.2 (1.6)	3.0 (1.5)	0.50
Total GCSI	3.0 (1.0)	2.7 (1.0)	0.02
Upper abdominal pain	3.1 (1.5)	3.2 (1.5)	0.86
Lower abdominal pain	2.2 (1.6)	2.2 (1.6)	0.90
GERD	2.0 (1.4)	1.8 (1.3)	0.31
Constipation	2.5 (1.8)	2.6 (1.7)	0.55
Diarrhea	1.8 (1.7)	1.5 (1.4)	0.07
PAGI-QOL
Total	2.5 (1.1)	2.8 (1.0)	0.05
SF-36
Physical	34 (11)	36 (12)	0.08
Mental	39 (13)	42 (13)	0.07
State-Trait An-xiety Inventory**
State score	44 (14)	41 (13)	0.14
Trait score	43 (12)	42 (12)	0.49
Beck’s Depression Index**
Score	18 (11)	16 (11)	0.15
Depressed	80 (20%)	14 (22%)	0.81
Medication use
Systemic corticosteroids	58 (13%)	9 (10%)	0.60
Prednisone	28 (6%)	6 (7%)	0.81
Narcotic pain medications	153 (34%)	22 (26%)	0.13
Neuropathic pain medications	113 (25%)	19 (22%)	0.59
Prokinetics	180 (40%)	30 (35%)	0.40
Antiemetics	13/230 (6%)	0/61 (0%)	0.08
NSAIDs	277 (62%)	59 (69%)	0.23
Prochloroperazine	28 (6%)	7 (8%)	0.48
Promethazine	126 (28%)	17 (20%)	0.14
Treatments
TPN	37 (8%)	2 (2%)	0.07
J tube	9 (2%)‡	5 (6%)§	0.06
G tube	3 (1%)¶	4 (5%)∥	0.01
Gastric stimulator	27 (6%)	4 (5%)	0.80
Smoking, drinking use
Ever smoked	161 (36%)	26 (30%)	0.39
Ever drink alcohol	203 (45%)	41 (48%)	0.72
Wireless motility capsule transit *	(n=144)	(n=29)
Gastric emptying-hrs	9.9 (14.7)	7.1 (7.4)	0.31
Small bowel – hrs	5.0 (3.1)	5.2 (5.1)	0.73
Colon – hrs	46.4 (36.6)	60.3 (50.5)	0.10

^*GpR2 only

^†Based on exact logistic regression

^‡Reasons for J tube include medication (n=1) and nutrition (n=8)

^§Reasons for J tube include hydration (n=1) and nutrition (n=4)

^¶Reasons for G tube include medication (n=2) and nutrition (n=1)

^∥Reasons for G tube include medication (n=1) and nutrition (n=3)

Table 3 shows the ANA results in patients with idiopathic gastroparesis in accordance with increasing ANA titers. Often, an ANA titer cut-off of > 1:160 is used to define a clinically significant positive ANA. Among 536 patients with idiopathic gastroparesis, a low ANA titer of 1:40 - 1:80 was seen in 33 (6%) patients, moderate titer of 1:160 - 1:320 in 36 (7%) patients, and high titer of ≥1:640 in 17 (3%) patients (Table 3). Increasing ANA titer was associated with female gender (p=0.05), Hispanic ethnicity (p=0.02), as well as the comorbidities of rheumatoid arthritis (p=0.02), Raynaud’s phenomenon (p=0.08) and incident SSc (p=0.004). 26 of 53 patients with ANA >1:160 had rheumatoid arthritis, scleroderma, SLE, CVD, Raynaud’s, other autoimmune disorders. The other 27 of the 53 patients with ANA > 1:160 did not have known autoimmune disorders at the time of enrollment.

Table 3.

Characteristics at enrollment by ANA titer in idiopathic patients with delayed gastric emptying

	ANA titer results
	Negative (n=450)	1:40 - 1:80 (n=33)	1:160 - 1:320 (n=36)	≥ 1:640 (n=17)	Trend P-value
	Mean (SD) / n (%)	Mean (SD) / n (%)	Mean (SD) / n (%)	Mean (SD) / n (%)
Demographics
White race	418 (93%)	30 (91%)	33 (92%)	15 (88%)	0.45
Female	395 (88%)	30 (91%)	34 (94%)	17 (100%)	0.05
Hispanic	37 (8%)	0 (0%)	3 (8%)	6 (35%)	0.02
Age - yrs	40 (14)	41 (12)	40 (13)	48 (15)	0.14
Married	243 (54%)	18 (55%)	21 (58%)	9 (53%)	0.78
BMI – kg/m2	26 (7)	25 (8)	27 (5)	26 (6)	0.94
Gp characteristics
Acute onset	195 (43%)	18 (55%)	16 (44%)	5 (29%)	0.71
Grade					0.41
1	71 (16%)	6 (19%)	8 (22%)	6 (35%)
2	292 (65%)	22 (69%)	23 (64%)	9 (53%)
3	84 (19%)	4 (12%)	5 (14%)	2 (12%)
Pattern					0.36
Chronic, stable	106 (24%)	6 (18%)	8 (22%)	4 (24%)
Chronic, worse	132 (29%)	5 (15%)	8 (22%)	3 (18%)
Chronic, improve	20 (4%)	2 (6%)	4 (11%)	0 (0%)
Chronic, periodic	129 (29%)	16 (48%)	11 (31%)	6 (35%)
Cyclic	61 (13%)	4 (12%)	5 (14%)	4 (24%)
Comorbidities
Arthritis	23 (5%)	2 (6%)	3 (8%)	4 (24%)	0.008
Scleroderma	5 (1%)	0 (0%)	1 (3%)	3 (18%)	0.004†
SLE*	7/370 (2%)	1/31 (3%)	1/35 (3%)	0/16 (0%)	1.00†
Collagen Vascular Dis*	0/370 (0%)	0/31 (0%)	0/35 (0%)	1/16 (6%)	0.07†
Raynaud’s Phenomena†	17/230 (7%)	2/20 (10%)	7/28 (25%)	1/13 (8%)	0.08†
Other autoimmune*	16/370 (4%)	1/31 (3%)	5/35 (14%)	0/16 (0%)	0.35†
GES
1 hr - %	81 (13)	81 (12)	83 (14)	78 (22)	0.88
2 hr - %	64 (16)	67 (14)	66 (18)	62 (22)	0.66
4 hr - %	28 (19)	28 (18)	28 (18)	26 (14)	1.00
Labs
CRP – mg/dL	0.9 (1.7)	0.8 (2.3)	1.2 (2.1)	0.3 (0.4)	0.89
CRP >10 mg/dL	3 (1%)	1 (3%)	0 (0%)	0 (0%)	0.92
ESR – mm/hr	14 (14)	15 (14)	18 (16)	24 (19)	0.005
ESR >22 mm/hr if male; >29 mm/hr if female	57 (13%)	6 (18%)	7 (19%)	6 (35%)	0.007
HbA1c - %	5.4 (0.5)	5.3 (0.4)	5.3 (0.6)	5.3 (0.6)	0.19
PAGI-SYM
GCSI
Nausea	3.4 (1.4)	3.4 (1.4)	3.1 (1.5)	2.7 (2.0)	0.02
Retching	1.8 (1.7)	1.7 (1.7)	1.0 (1.4)	0.9 (1.3)	0.001
Vomiting	1.8 (1.9)	1.5 (1.7)	1.1 (1.6)	1.0 (1.6)	0.003
Nausea subscale	2.4 (1.4)	2.2 (1.4)	1.7 (1.3)	1.5 (1.4)	0.0005
Stomach fullness	3.7 (1.2)	3.5 (1.5)	3.7 (1.0)	3.6 (1.3)	0.50
Unable to finish meal	3.6 (1.4)	3.3 (1.6)	3.4 (1.6)	3.4 (1.7)	0.19
Felt full after meal	3.7 (1.3)	3.4 (1.5)	3.8 (1.2)	3.5 (1.7)	0.53
Loss of appetite	3.0 (1.5)	2.9 (1.6)	2.8 (1.5)	2.0 (1.7)	0.01
Fullness subscale	3.5 (1.1)	3.3 (1.3)	3.4 (1.0)	3.1 (1.3)	0.10
Bloating	3.3 (1.6)	3.4 (1.6)	3.4 (1.4)	2.9 (1.4)	0.57
Stomach visibly larger	3.0 (1.7)	2.9 (1.8)	2.8 (1.6)	2.5 (1.5)	0.21
Bloating subscale	3.2 (1.6)	3.2 (1.6)	3.1 (1.4)	2.7 (1.3)	0.33
Total GCSI	3.0 (1.0)	2.9 (1.1)	2.7 (0.9)	2.5 (1.2)	0.007
Upper abdominal pain	3.1 (1.5)	3.3 (1.6)	3.1 (1.5)	3.1 (1.6)	0.99
Lower abdominal pain	2.2 (1.6)	2.4 (1.6)	2.0 (1.6)	2.1 (1.4)	0.65
GERD	2.0 (1.4)	2.2 (1.5)	1.4 (1.0)	1.8 (1.4)	0.13
Constipation	2.5 (1.8)	3.0 (1.7)	2.1 (1.7)	3.1 (1.7)	0.67
Diarrhea	1.8 (1.7)	1.6 (1.4)	1.5 (1.6)	1.4 (1.1)	0.06
PAGI-QOL
Total	2.5 (1.1)	2.8 (1.0)	2.8 (0.9)	2.7 (1.1)	0.09
SF-36
Physical	34 (11)	36 (12)	36 (12)	34 (13)	0.17
Mental	39 (13)	41 (13)	43 (13)	41 (15)	0.08
State-Trait An-xiety Inventory **
State score	44 (14)	43 (12)	37 (10)	46 (17)	0.22
Trait score	43 (12)	44 (12)	39 (11)	43 (15)	0.42
Beck’s Depression Index **
Score	18 (11)	16 (11)	15 (11)	18 (11)	0.28
Depressed	80 (20%)	6 (24%)	5 (19%)	3 (23%)	0.88
Medication use
Systemic corticosteroids	58 (13%)	1 (3%)	7 (19%)	1 (6%)	0.79
Prednisone	28 (6%)	1 (3%)	4 (11%)	1 (6%)	0.61
Narcotic pain medications	153 (34%)	8 (24%)	12 (33%)	2 (12%)	0.10
Neuropathic pain medications	113 (25%)	8 (24%)	7 (19%)	4 (24%)	0.54
Prokinetics	180 (40%)	16 (48%)	10 (28%)	4 (24%)	0.11
Antiemetics	13 (6%)	0 (0%)	0 (0%)	0 (0%)	0.08
NSAIDs	277 (62%)	22 (67%)	28 (78%)	9 (53%)	0.38
Prochloroperazine	28 (6%)	2 (6%)	4 (11%)	1 (6%)	0.50
Promethazine	126 (28%)	5 (15%)	10 (28%)	2 (12%)	0.15
Treatments
TPN	37 (8%)	1 (3%)	1 (3%)	0 (0%)	0.06
J tube	9 (2%)‡	2 (6%)§	3 (8%)∥	0 (0%)	0.14
G tube	3 (1%)¶	0 (0%)	3 (8%)††	1 (6%)‡‡	0.0003
Gastric stimulator	27 (6%)	2 (6%)	2 (6%)	0 (0%)	0.44
Smoking, drinking use
Ever smoked	161 (36%)	10 (30%)	12 (33%)	4 (24%)	0.29
Ever drink alcohol	203 (45%)	14 (42%)	21 (58%)	6 (35%)	0.72
Wireless motility capsule transit *	(n=144)	(n=10)	(n=14)	(n=5)
Gastric emptying -hrs	9.9 (14.7)	4.7 (2.0)	8.6 (9.2)	7.6 (8.9)	0.46
Small bowel – hrs	5.0 (3.1)	4.9 (2.3)	4.8 (2.9)	7.1 (11.8)	0.50
Colon – hrs	46.4 (36.6)	67.0 (71.6)	48.4 (25.8)	73.5 (45.0)	0.13

^*GpR2 only

^**GpR1 and GpR2 only

^†Based on exact logistic regression

^‡Reasons for J tube include medication (n=1) and nutrition (n=8)

^§Reasons for J tube include hydration (n=1) and nutrition (n=1)

^∥Reasons for J tube includes nutrition (n=3)

^¶Reasons for G tube include medication (n=2) and nutrition (n=1)

^††Reasons for G tube include medication (n=1) and nutrition (n=2)

^‡‡Reason for G tube includes nutrition (n=1)

ANA titer positivity was associated with lower total GCSI (p=0.007) and more so with lower nausea/vomiting subscale (p=0.0005), but was not related to gastric emptying scintigraphy at 2 or 4 hours (Table 3). ANA positivity was not related to differences in gastric emptying, small bowel transit, or colonic transit (p=0.13) using the wireless motility capsule.

ANA positivity associated with elevated ESR (p=0.007) but not with elevated CRP (p=0.92). We also looked at determinates of elevated ESR (defined as ESR >22 mm/hr if male or >29 mm/hr if female). An elevated ESR was significantly associated with older age, higher BMI, Hispanic ethnicity, elevated mean CRP and higher HgbA1c. In regard to symptoms, elevated ESR was associated with statistically significantly lower stomach fullness (p=0.02).

Multiple linear regression showed both total GCSI and nausea subscale scores were inversely associated (p<0.005) with increasing ANA titer adjusting for age, sex, ESR and gastric retention (Table 4).

Table 4.

Adjusted^* multiple linear regression of GCSI total and nausea subscale scores on ANA level

Outcome	Covariate	Units	Slope	95% CI	P-value
Total GCSI	ANA	ANA category score†	−0.18	−0.29, −0.05	0.005
	ESR	mm/hr	−0.002	−0.008, 0.004	0.60
	GES at 4 hrs	%	0.005	0.001, 0.010	0.03
	Female	vs male	0.60	0.32, 0.88	<0.001
	Age	Yr	−0.008	−0.014, −0.001	0.02
Nausea subscale	ANA	ANA category score†	−0.28	−0.44, −0.12	0.001
	ESR	mm/hr	0.005	−0.003, 0.013	0.23
	GES at 4 hrs	%	0.010	0.003, 0.016	0.003
	Female	vs male	0.17	−0.21, 0.54	0.38
	Age	yr	−0.021	−0.030, −0.013	<0.001

^*Model includes all covariates

^†ANA category score: 0=negative; 1=1:40 to 1:80; 2=1:160 to 1:320; 3= ≥1:640

Table 5 shows an additional analysis evaluating the patients with ANA values 1:160 or higher vs a negative ANA. In general, similar findings were noted. An ANA of 1:160 or greater was associated with Hispanic ethnicity, rheumatoid arthritis, scleroderma, and Raynaud’s phenomenon, less symptoms of nausea, retching, and vomiting, and treatment more often with gastrostomy tubes. We evaluated reasons for gastrostomy and jejunostomy tube placements. In general, gastrostomy tubes were used for medication administration and jejunostomy tubes were used for nutrition.

Table 5.

Characteristics at enrollment by ANA negative status vs ANA titer ≥ 1:160 in idiopathic patients with delayed gastric emptying

	ANA status
	Negative (n=450)	ANA ≥ 1:160 (n=53)	P-value
	Mean (SD) / n (%)	Mean (SD) / n (%)
Demographics
White race	418 (93%)	48 (91%)	0.57
Female	395 (88%)	51 (96%)	0.07
Hispanic	37 (8%)	9 (17%)	0.04
Age - yrs	40 (14)	42 (14)	0.29
Married	243 (54%)	30 (57%)	0.77
BMI – kg/m2	26 (7)	26 (6)	0.87
Gp characteristics
Acute onset	195 (43%)	21 (40%)	0.66
Grade			0.15
1	71 (16%)	14 (26%)
2	292 (65%)	32 (60%)
3	84 (19%)	7 (13%)
Pattern			0.52
Chronic, stable	106 (24%)	12 (23%)
Chronic, worse	132 (29%)	11 (21%)
Chronic, improve	20 (4%)	4 (8%)
Chronic, periodic	129 (29%)	17 (32%)
Cyclic	61 (13%)	9 (17%)
Comorbidities
Arthritis	23 (5%)	7 (13%)	0.03
Scleroderma	5 (1%)	4 (8%)	0.009
SLE*	7/370 (2%)	1/51 (2%)	1.00
Collagen Vascular Disease*	0/370 (0%)	1/51 (2%)	0.12
Raynaud’s phenomena†	17/230 (7%)	8/41 (20%)	0.03
Other autoimmune disorder*	16/370 (4%)	5/51 (10%)	0.16
GES
1 hr - %	81 (13)	81 (17)	0.94
2 hr - %	64 (16)	65 (19)	0.69
4 hr - %	28 (19)	28 (17)	0.97
Labs
CRP – mg/dL	0.9 (1.7)	1.0 (1.9)	0.77
CRP >10 mg/dL	3 (1%)	0 (0%)	1.00
ESR – mm/hr	14 (14)	20 (17)	0.007
ESR >22 mm/hr if male; >29 mm/hr if female	57 (13%)	13 (25%)	0.03
HbA1c - %	5.4 (0.5)	5.3 (0.6)	0.20
PAGI-SYM
Nausea	3.4 (1.4)	2.9 (1.7)	0.02
Retching	1.8 (1.7)	1.0 (1.4)	0.0007
Vomiting	1.8 (1.9)	1.1 (1.6)	0.004
Nausea subscale	2.4 (1.4)	1.7 (1.3)	0.0005
Stomach fullness	3.7 (1.2)	3.6 (1.1)	0.71
Unable to finish meal	3.6 (1.4)	3.4 (1.6)	0.26
Felt full after meal	3.7 (1.3)	3.7 (1.3)	0.90
Loss of appetite	3.0 (1.5)	2.5 (1.6)	0.03
Fullness subscale	3.5 (1.1)	3.3 (1.1)	0.21
Bloating	3.3 (1.6)	3.2 (1.4)	0.66
Stomach visibly larger	3.0 (1.7)	2.7 (1.5)	0.26
Bloating subscale	3.2 (1.6)	3.0 (1.4)	0.40
Total GCSI	3.0 (1.0)	2.7 (1.0)	0.01
Upper abdominal pain	3.1 (1.5)	3.1 (1.5)	0.89
Lower abdominal pain	2.2 (1.6)	2.0 (1.5)	0.49
GERD	2.0 (1.4)	1.5 (1.1)	0.03
Constipation	2.5 (1.8)	2.4 (1.7)	0.76
Diarrhea	1.8 (1.7)	1.4 (1.4)	0.09
PAGI-QOL
Total	2.5 (1.1)	2.8 (1.0)	0.12
SF-36
Physical	34 (11)	35 (12)	0.22
Mental	39 (13)	43 (13)	0.07
State-Trait Anxiety Inventory**
State score	44 (14)	40 (14)	0.11
Trait score	43 (12)	41 (12)	0.24
Beck’s Depression Index**
Score	18 (11)	16 (11)	0.30
Depressed	80/395 (20%)	8/40 (20%)	1.00
Medication use
Systemic corticosteroids	58 (13%)	8 (15%)	0.67
Prednisone	28 (6%)	5 (9%)	0.38
Narcotic pain medications	153 (34%)	14 (26%)	0.29
Neuropathic pain medications	113 (25%)	11 (21%)	0.61
Prokinetics	180 (40%)	14 (26%)	0.07
Antiemetics	13/230 (6%)	0 (0%)	0.23
NSAIDs	277 (62%)	37 (70%)	0.29
Prochloroperazine	28 (6%)	5 (9%)	0.38
Promethazine	126 (28%)	12 (23%)	0.52
Treatments
TPN	37 (8%)	1 (2%)	0.16
J tube	9 (2%)	3 (11%)	0.12
G tube	3 (1%)	4 (8%)	0.003
Gastric stimulator	27 (6%)	2 (4%)	0.76
Smoking, drinking use
Ever smoked	161 (36%)	16 (30%)	0.45
Ever drink alcohol	203 (45%)	27 (51%)	0.47
Wireless motility capsule transit *	(n=144)	(n=19)
Gastric emptying-hrs	9.9 (14.7)	8.4 (8.9)	0.65
Small bowel – hrs	5.0 (3.1)	5.4 (6.2)	0.64
Colon – hrs	46.4 (36.6)	56.2 (33.6)	0.31

^*GpR2 only

^†Based on exact logistic regression

In the 305 patients with idiopathic gastroparesis that were followed over 48 weeks (Table 6), increasingly positive ANA was associated with greater improvement in the severity of stomach visibly larger (p=0.02), stomach fullness (p=0.09), and bloating subscale (p=0.06) over 48 weeks. At the follow-up 48 week visit, there were significantly more patients with a subsequent diagnosis of autoimmune disorders and/or treatment for an autoimmune disorder who had an enrollment positive ANA, primarily those with ANA ≥1:160.

Table 6.

48-week baseline-adjusted changes in PAGI-SYM, PAGI-QOL and SF36 by ANA level at enrollment in idiopathic patients with delayed gastric emptying

	ANA titer results at enrollment
48-week baseline-adjusted changes	Negative (n=258)	1:40 - 1:80 (n=18)	1:160 - 1:320 (n=20)	≥ 1:640 (n=9)	Trend P-value
	Mean (SD) / n (%)	Mean (SD) / n (%)	Mean (SD) / n (%)	Mean (SD) / n (%)
PAGI-SYM
GCSI
Nausea
BL	3.3. (1.5)	3.4 (1.5)	3.2 (1.7)	2.7 (2.2)	0.28
48-week change	−0.6	−0.9	−0.7	−0.4	0.78
Retching
BL	1.9 (1.7)	1.8 (1.8)	0.8 (1.4)	1.1 (1.5)	0.008
48-week change	−0.4	−0.4	−0.8	−0.6	0.17
Vomiting
BL	1.7 (1.8)	1.7 (1.7)	1.0 (1.7)	1.1 (1.7)	0.06
48-week change	−0.4	−0.5	−0.7	−0.4	0.35
Nausea subscale
BL	2.3 (1.4)	2.3 (1.5)	1.6 (1.4)	1.6 (1.6)	0.02
48-week change	−0.4	−0.6	−0.7	−0.5	0.36
Stomach fullness
BL	3.6 (1.2)	3.7 (1.5)	3.7 (1.2)	3.6 (1.7)	0.96
48-week change	−0.4	−0.5	−0.5	−1.4	0.09
Unable to finish meal
BL	3.5 (1.5)	3.4 (1.6)	3.5 (1.5)	3.3 (1.9)	0.65
48-week change	−0.6	−0.8	−0.9	−0.9	0.29
Felt full after meal
BL	3.7 (1.4)	3.6 (1.7)	3.8 (1.2)	3.2 (2.0)	0.68
48-week change	−0.5	−0.4	−0.4	−0.7	0.91
Loss of appetite
BL	3.0 (1.6)	3.1 (1.6)	2.8 (1.7)	2.0 (1.5)	0.10
48-week change	−0.7	−0.6	−0.7	−0.3	0.59
Fullness subscale
BL	3.5 (1.2)	3.4 (1.4)	3.4 (1.1)	3.0 (1.6)	0.43
48-week change	−0.5	−0.6	−0.6	−0.8	0.54
Bloating
BL	3.3 (1.6)	3.4 (1.6)	3.4 (1.7)	2.7 (1.8)	0.56
48-week change	−0.2	−0.4	−0.5	−0.7	0.21
Stomach visibly larger
BL	2.9 (1.7)	3.1 (1.8)	2.9 (1.6)	2.2 (1.6)	0.47
48-week change	0.0	−0.3	−0.5	−0.7	0.02
Bloating subscale
BL	3.1 (1.6)	3.3 (1.6)	3.1 (1.6)	2.4 (1.6)	0.50
48-week change	−0.1	−0.4	−0.5	−0.7	0.06
Total GCSI
BL	3.0 (1.1)	3.0 (1.1)	2.7 (1.0)	2.4 (1.5)	0.11
48-week change	−0.4	−0.5	−0.6	−0.6	0.16
Upper abdominal pain
BL	3.1 (1.5)	3.3 (1.9)	2.9 (1.5)	3.2 (1.7)	0.92
48-week change	−0.6	−0.3	−0.8	−0.8	0.59
Lower abdominal pain
BL	2.1 (1.5)	2.2 (1.6)	2.1 (1.8)	1.8 (1.3)	0.69
48-week change	−0.2	0.1	−0.9	−0.2	0.20
GERD
BL	1.9 (1.4)	2.3 (1.5)	1.2 (0.9)	1.8 (1.4)	0.13
48-week change	−0.3	−0.1	−0.4	−0.1	0.76
Constipation
BL	2.4 (1.8)	3.1 (1.6)	2.3 (1.8)	3.4 (1.3)	0.16
48-week change	−0.1	−0.2	−0.7	−0.3	0.11
Diarrhea
BL	1.9 (1.7)	1.5 (1.4)	1.4 (1.7)	1.2 (1.1)	0.07
48-week change	−0.2	0.4	−0.5	0.6	0.28
PAGI-QOL
BL	2.6 (1.1)	2.7 (1.1)	2.9 (1.0)	2.6 (1.2)	0.35
48-week change	0.3	−0.3	0.5	0.3	0.99
SF-36
Physical
BL	34 (10)	37 (10)	37 (13)	36 (12)	0.21
48-week change	1.6	−0.8	0.6	−3.5	0.06
Mental
BL	40 (13)	40 (14)	45 (11)	39 (17)	0.37
48-week change	1.8	−5.3	1.4	5.7	0.95
Newly diagnosed or treated at 48-week visit *
Rheumatoid Arthritis	13/268 (5%)	0/18 (0%)	1/21 (5%)	2/10 (20%)	0.22
Scleroderma	2/268 (1%)	0/18 (0%)	0/21 (0%)	2/10 (20%)	0.0007
SLE†	4/236 (2%)	0/17 (0%)	1/21 (5%)	0/10 (0%)	0.80
Collagen vascular disorder†	2/236 (1%)	0/17 (0%)	0/21 (0%)	0/10 (0%)	0.56
Raynaud‡	4/117 (3%)	0/10 (0%)	3/15 (20%)	2/6 (33%)	0.0004
Other autoimmune†	3/236 (1%)	0/17 (0%)	2/21 (10%)	1/10 (10%)	0.005

Among this table of patients with complete data for ANA at baseline:

1) The header row in Table 5 shows patients with complete data at baseline and f48 for GCSI.

2) The autoimmune rows show patients with complete data at f48 for Follow-up Medical History

^*Patients with a completed 48-week Follow-up Medical History form

^†Item not included in GpR1 Follow-up Medical History form revisions 1 and 2

^‡Item not included in GpR1 Follow-up Medical History form revisions 1, 2 and 3

We looked broadly at “autoimmune gastroparesis”, defining this entity as a patient with delayed gastric emptying with a positive ANA and/or an AIRD. Table 7 shows the result of this analysis. There were 21 patients with delayed gastric emptying with a positive ANA with an autoimmune disorder. Compared to gastroparesis patients with negative ANA, or gastroparesis patients with positive ANA but no autoimmune disorder, these patients with “autoimmune gastroparesis” had higher ESR (p=0.02). These “autoimmune gastroparesis” patients had less severe loss of appetite, vomiting, and total GCSI.

Table 7.

Characteristics of patients at enrollment by negative ANA vs positive ANA without autoimmune disease vs positive ANA with autoimmune disease

	Negative ANA (n=450)	Positive ANA without autoimmune disorder (n=65)	Positive ANA with autoimmune disorder (n=21‡)	Trend P-value
	Mean (SD) / n (%)	Mean (SD) / n (%)	Mean (SD) / n (%)
Demographics
White race	418 (93%)	59 (91%)	19 (90%)	0.50
Female	395 (88%)	61 (94%)	20 (95%)	0.09
Hispanic	37 (8%)	5 (8%)	4 (19%)	0.23
Age - yrs	40 (14)	41 (14)	45 (12)	0.16
Married	243 (54%)	36 (55%)	12 (57%)	0.73
BMI – kg/m2	26 (7)	26 (7)	25 (6)	0.68
Gp characteristics
Acute onset	195 (43%)	30 (46%)	9 (43%)	0.82
Grade				0.37
1	71 (16%)	16 (25%)	4 (19%)
2	292 (65%)	40 (62%)	14 (67%)
3	84 (19%)	8 (12%)	3 (14%)
Pattern				0.12
Chronic, stable	106 (24%)	14 (22%)	4 (19%)
Chronic, worse	132 (29%)	9 (14%)	7 (33%)
Chronic, improve	20 (4%)	4 (6%)	2 (10%)
Chronic, periodic	129 (29%)	29 (45%)	4 (19%)
Cyclic	61 (13%)	9 (14%)	4 (19%)
GES
1 hr - %	81 (13)	82 (15)	78 (16)	0.77
2 hr - %	64 (16)	67 (15)	60 (22)	0.87
4 hr - %	28 (19)	29 (19)	25 (13)	0.90
Labs
CRP – mg/dL	0.9 (1.7)	0.8 (1.8)	1.4 (2.6)	0.58
CRP >10 mg/dL	3 (1%)	1 (2%)	0 (0%)	0.83
ESR – mm/hr	14 (14)	17 (16)	20 (17)	0.02
ESR >22 mm/hr if male; >29 mm/hr if female	57 (13%)	14 (22%)	5 (24%)	0.03
HbA1c - %	5.4 (0.5)	5.3 (0.5)	5.1 (0.5)	0.05
PAGI-SYM
GCSI
Nausea	3.4 (1.4)	3.1 (1.5)	3.1 (1.8)	0.08
Retching	1.8 (1.7)	1.2 (1.5)	1.3 (1.6)	0.01
Vomiting	1.8 (1.9)	1.3 (1.7)	1.1 (1.6)	0.008
Nausea subscale	2.4 (1.4)	1.9 (1.3)	1.9 (1.4)	0.005
Stomach fullness	3.7 (1.2)	3.5 (1.3)	3.7 (0.8)	0.45
Unable to finish meal	3.6 (1.4)	3.3 (1.7)	3.5 (1.4)	0.25
Felt full after meal	3.7 (1.3)	3.6 (1.4)	3.7 (1.2)	0.43
Loss of appetite	3.0 (1.5)	2.9 (1.6)	2.0 (1.5)	0.01
Fullness subscale	3.5 (1.1)	3.3 (1.3)	3.2 (1.0)	0.09
Bloating	3.3 (1.6)	3.3 (1.5)	3.3 (1.5)	0.90
Stomach visibly larger	3.0 (1.7)	2.8 (1.7)	3.0 (1.7)	0.41
Bloating subscale	3.2 (1.6)	3.0 (1.5)	3.1 (1.5)	0.60
Total GCSI	3.0 (1.0)	2.7 (1.0)	2.7 (1.1)	0.03
Upper abdominal pain	3.1 (1.5)	3.1 (1.6)	3.5 (1.4)	0.57
Lower abdominal pain	2.2 (1.6)	2.2 (1.6)	2.0 (1.6)	0.73
GERD	2.0 (1.4)	1.7 (1.3)	2.2 (1.3)	0.71
Constipation	2.5 (1.8)	2.7 (1.7)	2.5 (1.7)	0.66
Diarrhea	1.8 (1.7)	1.4 (1.3)	1.8 (1.6)	0.16
PAGI-QOL
Total	2.5 (1.1)	2.7 (1.0)	2.9 (0.9)	0.04
SF-36
Physical	34 (11)	38 (11)	29 (12)	0.70
Mental	39 (13)	41 (12)	47 (16)	0.02
State-Trait Anxiety Inventory **
State score	44 (14)	41 (13)	40 (14)	0.13
Trait score	43 (12)	42 (12)	41 (12)	0.45
Beck’s Depression Index **
Score	18 (11)	16 (11)	17 (10)	0.22
Depressed	80 (20%)	11 (23%)	3 (17%)	0.99
Medication use
Systemic corticosteroids	58 (13%)	5 (8%)	4 (19%)	0.92
Prednisone	28 (6%)	4 (6%)	2 (10%)	0.66
Narcotic pain medications	153 (34%)	12 (18%)	10 (48%)	0.58
Neuropathic pain medications	113 (25%)	13 (20%)	6 (29%)	0.78
Prokinetics	180 (40%)	22 (34%)	8 (38%)	0.48
Antiemetics	13 (6%)	0 (0%)	0 (0%)	0.16
NSAIDs	277 (62%)	44 (68%)	15 (71%)	0.20
Prochloroperazine	28 (6%)	5 (8%)	2 (10%)	0.47
Promethazine	126 (28%)	12 (18%)	5 (24%)	0.19
Treatments
TPN	37 (8%)	1 (2%)	1 (5%)	0.10
J tube	9 (2%)	4 (6%)	1 (5%)	0.08
G tube	3 (1%)	2 (3%)	2 (10%)	0.0003
Gastric stimulator	27 (6%)	3 (5%)	1 (5%)	0.65
Smoking, drinking use
Ever smoked	161 (36%)	17 (26%)	9 (43%)	0.67
Ever drink alcohol	203 (45%)	31 (48%)	10 (48%)	0.68
Wireless motility capsule transit *	(n=144)	(n=19)	(n=10)
Gastric emptying -hrs	9.9 (14.7)	5.7 (5.5)	9.6 (9.9)	0.49
Small bowel – hrs	5.0 (3.1)	6.0 (5.8)	3.9 (3.4)	0.82
Colon – hrs	46.4 (36.6)	60. 1(56.8)	61.0 (35.6)	0.12

^*GpR2 only

^**GpR1 and GpR2 only

^†Based on exact logistic regression

^‡Includes 6 patients with Raynaud only, 4 patients with arthritis only, 2 patients with other autoimmune only, 1 patient with scleroderma only, 1 patient with arthritis only and 1 patient each with the following multiple diagnoses: Raynaud + other autoimmune; SLE + other autoimmune; Raynaud + scleroderma; arthritis + other autoimmune; arthritis + scleroderma + Raynaud; arthritis + scleroderma + collagen; arthritis + SLE + Raynaud + other autoimmune

Discussion

This study reports that ANA positivity was seen in 17% of patients with gastroparesis, with similar prevalence among idiopathic, diabetic, and postfundoplication gastroparesis. Among idiopathic patients, ANA positivity was associated with female sex, Hispanic ethnicity, arthritis, SSc, Raynaud’s, and elevated ESR. There was a negative association of ANA titers with gastroparesis symptom severity, so that higher ANA titers were associated with lower symptom severity. There was no association of ANA positivity with the degree of gastric emptying impairment by either scintigraphy or WMC.

The presence of ANA does not confirm a diagnosis of systemic lupus erythematosus (SLE), although the ANA is a very sensitive screening test for SLE: 99% of patients with SLE have a positive ANA, and a lack of ANA makes SLE diagnosis much less likely (2). Positive ANAs are also present people with other autoimmune diseases, such as Hashimoto’s, SSc and rheumatoid arthritis among others. Moreover, up to 15% of healthy women may have a positive ANA, and the majority of these people will never develop any signs of lupus. ANA titers of less than or equal to 1:40 are often considered negative and those ≥1:160 are considered clinically relevant. Our primary analysis was comparing gastroparesis patients with positive ANA to those with negative ANA. We did not have a normal healthy subject control group, which could be considered a limitation of this study. Interestingly, in our study as in others, patients with gastroparesis were predominately women, and the titer with ANA was significantly associated with female gender.

Systemic lupus erythematosus (SLE) is often listed as one of the rare causes of gastroparesis (4). In SLE, gastrointestinal symptoms are varied and can involve any part of the GI tract; esophageal dysmotility and intestinal pseudo-obstruction are often described. Interestingly, there are few direct reports of gastric dysmotility or gastroparesis in SLE; most publications are case reports. In a recent retrospective study, using the Healthcare Cost and Utilization Project: Nationwide Inpatient Sample (HCUP-NIS) data from the year 2013–2014, a total of 27,543 patients with the diagnosis of idiopathic gastroparesis were identified (5). Conditions that were found to be linked with nondiabetic, non-post-surgical gastroparesis were: chronic pancreatitis, end stage renal disease, irritable bowel syndrome, SLE, fibromyalgia, and venous thromboembolism. SLE comprised 824 of the patients (3%) with idiopathic (nondiabetic) gastroparesis. This article suggested that gastroparesis may be a possible late-onset or severe manifestation of SLE. Studies attempting to alleviate gastroparesis by treating the underlying SLE have shown limited success, suggesting that either the gastroparesis is irreversible, shows a delayed response to treatment in SLE patients, or is unrelated to the SLE (23).

False positive ANA can also occur with certain medications (24). Drugs that may cause a false-positive ANA test include: acetazolamide, aminosalicylic acid, chlorothiazides, chlorprothixene, griseofulvin, hydralazine, penicillin, phenylbutazone, phenytoin, procainamide, streptomycin, sulfonamides, and tetracyclines. Drugs that may cause a false-negative test include steroids. Medications reported to have a definite relationship to drug induced lupus include the following: hydralazine, procainamide, isoniazid, methyldopa, quinidine, minocycline, chlorpromazine, and tumor-necrosis factor (TNF) alpha inhibitors. Medications used for gastroparesis are not typically involved in causing false positive ANAs or drug induced lupus. Chlorpromazine is an antipsychotic medication that is occasionally used for nausea and vomiting. We did not ascertain exposure to this medication. If an ANA test is positive, a panel of tests may be done to identify antibodies to specific nuclear antigen targets that can signal the presence of specific autoimmune conditions. These were not assessed in our study.

This study shows that ANA positivity in patients with gastroparesis was associated with the presence of rheumatoid arthritis, SSc and Raynaud’s phenomenon. This is not unexpected since ANA positivity is high in SLE, scleroderma, and Raynaud’s phenomenon. Patients underwent detailed evaluation of their gastroparesis but did not have a standardized evaluation for rheumatologic diseases and we did not record treatments for rheumatologic disorders. Based on our observations, we suggest that detection of a positive ANA ≥1:160 in a patient with gastroparesis should prompt referral to rheumatology for evaluation of a possible underlying autoimmune disorder.

There was a negative association between gastroparesis symptom severity (nausea, retching, vomiting, loss of appetite, diarrhea) and ANA titer (higher titer with less symptoms). Why this is, is not clear, as there was no association of the ANA with gastric emptying. However, symptoms of gastroparesis overall are correlated poorly with gastric emptying (25).

Positive ANA in gastroparesis was associated with elevated ESR. Perhaps the positive ANA and elevated ESR is reflective of an inflammatory process involving the stomach and perhaps worsening gastroparesis. Our GpCRC pathology studies show that an inflammatory infiltrate involving macrophages occurs in the myenteric plexus in patients with gastroparesis (26). Alternatively, the association of the ANA with ESR in our patients with gastroparesis could be from their underlying comorbid disorder, such as arthritis, SSc, and Raynaud’s phenomenon.

In idiopathic gastroparesis patients followed over 48 weeks, increasingly positive ANA was associated with greater improvement in scores for stomach visibly larger and stomach fullness over 48 weeks. In these patients, there was also at baseline an increase in diarrhea in the patients with high titers. Perhaps these symptoms could be related to small intestinal bacterial overgrowth (SIBO) which can occur in gastroparesis patients (27,28). Patients with higher ANA values had higher rates of gastrostomy tube use although these are low numbers. We do not have direct information whether ANA positivity altered patient management. In general, the ANA positive gastroparesis patients used gastrostomy tubes for medication and jejunostomy tubes for nutrition. In addition, we found that when followed over 48 weeks, gastroparesis patients with positive ANA values subsequently were given more often an autoimmune diagnosis or received treatment for an autoimmune disorder, presumably after referral to a rheumatologist.

Whether the ANA might be a marker for diffuse GI dysmotility in patients with gastroparesis is not known. Autoimmune GI dysmotility (AGID) is a recently described clinical entity with GI symptoms, gastrointestinal dysmotility, and positive autoimmune tests (1). The AGID Antibody Panel of Mayo Clinic involves testing for numerous antibodies. In a retrospective case study of patients seen at Mayo Clinic for suspected AGID, 17 of the 23 patients improved after a 6 to 12 week immunotherapy trial (generally IVIG). Autoimmune serological evaluation revealed a neural-specific antibody in 12 of the 17 responders (71 percent). Symptomatic improvements were generally accompanied by objective evidence of improved GI motility and autonomic function (1). Other centers have also reported use of intravenous immunoglobulin in refractory patients with the symptoms of gastroparesis and suspected autoimmune gastroparesis (29,30). Further evaluation of the role of immune markers in gastroparesis seems warranted.

In conclusion, this observational registry study assessed a large number of patients with gastroparesis in multiple academic centers for ANA positivity. ANA-positive gastroparesis represents a subset of gastroparesis patients who often have other autoimmune symptoms or disorders. Patients often have less severe symptoms, particularly nausea and vomiting. When patients are followed over time, ANA-positive gastroparesis was associated with greater improvement in stomach visibly larger, stomach fullness, bloating subscale over 48 weeks compared to patients who are ANA negative.

Data availability statement:

The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.