Table 2.

Characteristics of included studies (n = 19)

First author + data collection method+ quality points	Setting	Characteristics research group (number, age, sex, impairment)	Reference test	Verification bias possible?	Selection bias possible?	Spectrum bias possible?
Böhmer et al. [21] Inspection of teeth + reference test q.p. = 5	Random selection of residents with IQ < 50 of 3 institutes for mentally retarded people	GERD group: 28 Control group: 35 (tested negative for GER) Mean age 22.8 years. 48% males, 52% females IQ < 50	24 hour pH test	No	No	No
Böhmer et al. [10] Review of record q.p. = 4	All residents with IQ < 50 of 5 institutes for mentally retarded people	GERD group: 107 Control group: 1,580 (1,518 subjects not tested for GER and 62 subjects tested negative for GER) Mean age 35.3 years (range 2–92 years). 61% males, 39% females IQ < 50	Endoscopy	Yes	No	No
Böhmer et al. [17] Questionnaire + reference test q.p. = 3	Residents of 1 institute for mentally retarded people with IQ < 50 and with symptoms of GER	GERD group: 57 Control group: 46 (tested negative for GER) Mean age 38.4 years (range 4–75 years) 63% males, 37% females IQ < 50	24 hour pH test	No	Yes	Yes
Böhmer et al. [7] Questionnaire + reference test q.p. = 5	Persons with IQ < 50 randomly selected in six also randomly selected institutes for people with intellectual disability.	GERD group: 186 persons Control group: 200 persons (tested negative for GER) Mean age 35 years, 40% females IQ < 50	24 hour pH test	No	No	No
Cameron et al. [23] Review of records q.p. = 2	All subjects without GER who received a gastronomy tube Evaluation of an intervention	Intervention group: 63 children Mean age 3.5 years (range 1 month-17 years) Sex: 52% males, 48% females All children were neurologically impaired	Pretest: UGI-studies, pH test, or esophageal biopsy Post test: ?	Yes	No	Yes
Field et al. [13] Review of records q.p. = 2	All children referred to an interdisciplinary feeding program for the evaluation of feeding problems	GERD group: 178 children Control group: 171 children tested negative or not tested Median age 13–36 months (range 1 month-12 years) 57% boys, 43% girls. 64% with developmental disabilities	Diverse: in most cases endoscopy, pH test and/or radiographic studies	Yes	No	Yes
Gustafsson et al. [11] Review of records + reference test q.p. = 3	All children who visited an outpatient clinic It is not clear for what reasons the children visited the outpatient clinic	GERD group: 25 children Control group: 7 children negatively tested Mean age 11.2 years (range 0.7 – 19 years). 34% boys, 66% girls. All have cerebral palsy with severe brain damage (66%) or severe mental retardation with cerebral atrophy (34%)	24 hours pH test	No	No	Yes
Halpern et al. [19] Review of records and/or questionnaire by parents q.p. = 4	All children referred to a pediatric surgical service for detection, quantification or surgical treatment of GER	GERD group: 69 children Control group: 57 children negatively tested Age range 1 – 16 years. Sex: ? Impairment: 36% CNS disease	18–24 hours pH test	No	No	Yes
Heine et al. [24] Questionnaire + review of records q.p. = 2	All children without or with mild GER after gastronomy Evaluation of an intervention.	Intervention group: 30 children Mean age 6 years (range 3 months-17 years) Sex: 60% boys, 40% girls All children were neurologically impaired 23 had intellectual disability	Pretest: 24 hours pH test + esophageal biopsy Post test: Probably 24 hours pH test + endoscopy	No	No	Yes
Lin et al. [20] Interview (parent) + reference test (to check if the selection was correct) q.p. = 2	All children diagnosed as GERD patients in the University Hospital	GERD group: 34 children. No control group Median age 2.5 years (range 1.1–9.7 years) 53% boys, 47% girls 14 children had a neurological disorder, 10 had other diseases, 10 did not have an underlying disease	24 hour pH test	Yes	No	Yes
Luzzani et al. [12] Questionnaire + reference test q.p. = 2	Patients with Cornelia de Lange Syndrome Strategy of recruitment is unclear	GERD group: 28 Control group: 15 with normal pH test Mean age 6.5 years (range 1 month- 30 years) 18 males and 25 females	24 hour pH test and endoscopy	No	Yes	Yes
Martinez et al. [18] Review of records q.p. = 1	Subjects with antireflux operation and after operation tested with a reference test	GERD group: 47 children Control group: 55 children tested negative Age: children over 2 years of age. Sex: ? All have severe cognitive and motor impairment	Diverse: upper gastrointestinal contrast study (barium), nuclide chalasia scan, upper endoscopy, extended pH study	Yes	Yes	Yes
Orchard et al. [15] Review of records q.p. = 3	All persons who reside in a long-term care facility and are admitted to a hospital with UGI tract bleeding	GERD group: 28 adults Control group: 12 adults Mean age 42 years, 78% males All are mentally retarded, 87% with IQ < 35–40	endoscopy	No	No	Yes
Ravelli et al. [16] Reference test, it is not clear how symptoms were measured q.p. = 2	Children who suffered retching and/or vomiting and were referred to a hospital for suspected gastrointestinal disorder	GERD group: 13 children Control group: 6 children Age: approx. 4.5 years Sex: approx. 50% boys All children selected for this review have CNS disorder and do not suffer gastric dysrhythmias	24 hour pH test and endoscopy	No	Yes	Yes
Rogers et al. [14] Reference test + questionnaire about regurgitation to select subjects q.p. = 2	Subjects living in a residential facility with a history of regurgitating food into the mouth for a minimum of 3 months	GERD group: 16 adults Control group: 7 adults negatively tested Age range 28–65 years 10 males, 13 females All with severe developmental disabilities 61% had cerebral palsy	Radiological studies	No	Yes	No
Shaw et al. [22] Observation of teeth + reference test q.p. = 2	Children attending a dental outpatient clinic of a hospital	GERD group: 12 children. Control group: 9 children with normal pH test Mean age 12.5 years (range 3.9 – 20.7 years) Sex: ? All have cerebral palsy	24 hour pH test	No	Yes	Yes
Wadie et al. [25] Review of records q.p. = 1	All subjects without GER who received a gastronomy tube Evaluation of an intervention.	Intervention group: 56 children Mean age 4.4 years Sex: ? All children were neurologically impaired	Pretest: upper gastrointestinal studies, sometimes followed by a milk scan Post test: ?	Yes	No	Yes
Van Winckel [9] Interview with caregivers + review of records + reference test q.p. = 3	All children of a Pediatric Institute with IQ < 30 combined with severe motor disorders	GERD group: 46 children (45 with symptoms of GERD and tested positive + 1 asymptomatic child that is tested positively) Control group: 38 children (9 with symptoms but negative reference test, 2 without symptoms and negative reference test, 12 without symptoms and not tested, 15 with symptoms but not tested because parents refused the test) Mean age 13 years (range 2–18 years) 52% boys, 48% girls IQ < 30 combined with severe motor disorders	24 hour pH test and endoscopy	Yes	No	Yes
Vega Gutierrez et al. [26] Review of records q.p. = 2	All children with neurological or psychiatric problems who visited an neuropediatric outpatient clinic	GERD group: 27 children Control group: 113 children, not tested or negatively tested Median age 7.7 years (range 8 months-18 years) 67% boys, 33% girls; 32% had moderate to severe mental retardation	Barium ingestion with fluoroscopy and/or eso-phascopy	Yes	No	Yes

? information not found in publication