Aldosterone Levels Post-IV Saline Suppression Using Commercial Reference Laboratory Liquid Chromatography-Tandem Mass Spectrometry Assay

Abstract

Background/Objective

Diagnostic cutoffs for primary aldosteronism (PA) post-intravenous (IV) saline suppression have not been well established. These cutoffs are based on old immunoassays and, more recently, on liquid chromatography tandem mass spectrometry (LC-MS/MS) assays performed in research settings. Aldosterone levels associated with PA post-IV saline suppression using commercially available reference laboratory LC-MS/MS assays are unknown. Our objective was to report our experience measuring aldosterone levels postsaline infusion using a commercial reference laboratory LC-MS/MS assay.

Methods

A retrospective chart review was conducted. A total of 35 patients who underwent a saline suppression test with aldosterone levels measured using a commercial reference laboratory LC-MS/MS assay were included. Patients were classified into 2 groups: no PA (n = 9) and confirmed PA (n = 26) based on postsurgical outcomes (histopathology and PA surgical outcome criteria) and, for those on medical treatment, clinical and biochemical response to therapy. Aldosterone levels at baseline and after 2 L of IV normal saline infusion over 4 hours were analyzed and compared between the groups.

Results

Median baseline aldosterone levels were higher in patients with confirmed PA, 16.0 ng/dl (IQR: 14.0, 26.0) versus 11.0 ng/dl (IQR: 6.0, 13.0), P = 0.016. The median aldosterone levels postsaline infusion in the confirmed PA group were 11.5 ng/dl (IQR: 8.0, 18.0) compared to 1.0 ng/dl (IQR: 1.0, 2.0) in the no PA group. In the latter, none of the patients had an aldosterone level >3.0 ng/dl.

Conclusion

Using an LC-MS/MS aldosterone assay from a commercial reference laboratory, we report that saline suppression in patients with confirmed PA can detect aldosterone levels as low as 4.0 ng/dl. These results need to be confirmed with larger studies.

Highlights

• •Commercial liquid chromatography tandem mass spectrometry is replacing immunoassays to measure aldosterone concentrations
• •In primary aldosteronism (PA), aldosterone levels post-saline suppression test (SST) were found lower than the traditional diagnostic cutoffs of 5-10 ng/dl
• •Consideration of the assay is fundamental when interpreting SST results
• •These results could help clinicians avoid false negative interpretations in patients with PA

Clinical Relevance

We describe a cohort of patients with primary aldosteronism where the saline suppression test was performed using commercial laboratory liquid chromatography tandem mass spectrometry, resulting in aldosterone levels as low as 4 ng/dl, lower than the traditional aldosterone cutoff values of 5-10 ng/dl.

Introduction

Primary aldosteronism (PA) is the most common cause of endocrine hypertension. It has been associated with cardiovascular, renal, and metabolic complications.1, 2, 3, 4, 5 To prevent these major health consequences, it is essential to establish its diagnosis. Screening for PA involves measuring aldosterone concentrations and plasma renin activity (PRA) or direct renin concentration, ideally during a state of normokalemia. An aldosterone/PRA ratio >20-40 has been suggested as a positive screening test for the evaluation of patients suspected to have PA.⁶ However, both the aldosterone and renin components should be assessed individually. Most patients with overt PA have a PRA <1.0 ng/ml/h in the absence of mineralocorticoid receptor antagonist (MRA) use.⁷

Multiple confirmatory tests have been developed over the years. Of these, the fludrocortisone suppression test usually requires hospital admission and is therefore not performed in routine clinical practice. The furosemide upright test is mainly performed in East Asia.⁸ In the United States, the most commonly performed dynamic testing includes the oral sodium loading test, the saline suppression test (SST), and to a lesser extent, the captopril challenge test (CCT). These confirmatory tests have limitations. The oral sodium loading test relies on appropriate sodium intake and 24-hour urine collection, and there are reports that the CCT may be associated with high false-positive test results.⁶ Of note, both OST and SST are relatively contraindicated in patients with severe uncontrolled hypertension.⁶

At the present time, there is a lack of consensus regarding cutoff values for aldosterone during dynamic testing that are diagnostic for PA. One important reason for this is the difference between aldosterone assays. Initially, aldosterone concentrations were measured using immunoassays; however, liquid chromatography tandem mass spectrometry (LC-MS/MS) methods for aldosterone have become increasingly available in a number of reference laboratories. The latest Endocrine Society guidelines recommended post-saline infusion aldosterone levels >10 ng/dl (277.4 pmol/l), and historically an aldosterone cutoff >5-10 ng/dl has been used to confirm PA post-SST, mostly based on immunoassays. The Endocrine Society guidelines indicated that a cutoff of 6.8 ng/dl (190 pmol/l) has the best balance between sensitivity and specificity.⁶ Another group using immunoassays has suggested that PA is highly likely with aldosterone levels 4 hours postsaline infusion >7.82 ng/dl (217 pmol/l) and could be excluded if aldosterone levels is <6.16 ng/dl (171 pmol/l).⁹ A recent systematic review of the literature and meta-analysis confirmed the diagnostic challenges and the limitation of these tests, including the use of predefined aldosterone cutoffs to establish the diagnostic accuracy of dynamic tests.¹⁰

In our center, the most frequently performed confirmatory test for PA is the SST. To date and to our knowledge, there are no data on the aldosterone levels post-SST in patients with PA using a commercially available LC-MS/MS in the United States. The objective of our study was to report our experience with measuring aldosterone levels post-SST using an LC-MS/MS assay from a commercial reference laboratory (Quest Diagnostics).

Methods

We performed a retrospective chart review using electronic medical records of patients who underwent intravenous SST at our institution between 2015 and 2024. The LC-MS/MS assay has been utilized to measure aldosterone levels since 2015 in our affiliated commercial reference laboratory (Quest Diagnostics). We included adult patients aged 18 years and older who underwent the SST as part of the PA workup. To confirm the diagnosis of PA in those that underwent adrenalectomy, we used postoperative day 1 aldosterone level <3 ng/dl and positive immunostaining for CYP11B2, as well as the PA surgical outcome criteria that include a significant improvement in blood pressure (BP) control, reduction in the number of BP medications, resolution of hypokalemia, improvement in plasma renin activity, aldosterone (aldosterone-renin ratio), and discontinuation of MRA.¹¹ Hypokalemia was defined as serum potassium of <3.5 mmol/l. For patients who did not undergo adrenalectomy and were medically managed with MRAs, PA was confirmed by significant improvement in BP, a decrease in the number of antihypertensive medications, resolution of hypokalemia, and an increase in plasma renin activity after the initiation of MRA.¹² In some cases, a consensus was reached among 3 endocrinologists to define the presence or absence of PA by reviewing the response to MRA, a rise in PRA level after adjusting the non-MRA medications, and the result of other confirmatory tests. The patients with a lack of adequate clinical information or follow-up were excluded from the study. Accordingly, we did not use a predefined diagnostic threshold criterion for aldosterone levels post-SST. All patients with an adrenal nodule underwent a 1 mg of dexamethasone suppression test. The study was approved by the Johns Hopkins University Institutional Review Board (IRB00415476).

Saline Suppression Test Protocol

Patients meeting criteria underwent SST as part of their standard of care at our institution. Prior to confirmatory testing, antihypertensive agents were switched to one or more of the non-RAAS modifying agents, including doxazosin, verapamil, and/or hydralazine. MRAs were discontinued for at least 4 weeks prior to testing.

The SST was performed in the morning. Patients were kept in a seated position for at least 30 minutes before and during the infusion of 2 liters of normal saline over 4 hours. Aldosterone levels were measured at baseline and 4 hours postsaline infusion. In most cases, baseline PRA and pre- and post-saline infusion cortisol levels were measured on the day of SST (26/35, 77.1%). For patients with hypokalemia, potassium supplementation was provided to ensure a state of normokalemia before the SST. Vital signs, BP, and heart rate were determined at baseline, at the end of each 1-liter intravenous bag, and when clinically indicated. If systolic BP levels exceeded 180 mmHg or diastolic 100 mmHg, oral hydralazine was provided.

Measurements of Aldosterone and Renin Activity

Serum aldosterone concentrations (ng/dl) and plasma renin activity (ng/ml/h) were determined using liquid chromatography tandem mass spectrometry at Quest Diagnostics as previously described.^13,14 The limit of quantitation for the aldosterone assay is 1 ng/dl with intra-assay precision of 1.83% to 6.21% and interassay precision of 2.73% to 4.36% over the range of 10-1000 ng/dl.¹⁴ The limit of quantitation for the PRA is 0.1 ng/ml/h with intra-assay precision of 5.0% to 6.6% and interassay precision of 3.7% to 5.4% over the range of 2.5-12.0 ng/ml/h.¹³

Statistical Analysis

Descriptive statistics were used to summarize patient demographic characteristics and clinical outcomes. The normality of the data was assessed using skewness tests and the Shapiro-Wilk test. For variables that were not normally distributed, results are presented as medians with IQRs, with ranges also provided for aldosterone levels. The correlation between patient characteristics and the diagnosis of PA was examined using Pearson χ², Fisher exact tests, t tests, and Kruskal-Wallis tests as appropriate. Receiver operating characteristic analysis was also conducted to evaluate the diagnostic performance of postsaline aldosterone levels and to estimate an optimal cutoff using Youden index. Analyses were performed using Stata Statistical Software Version 18.0 (StataCorp LLC), with statistical significance set at P value of <0.05.

Results

A total of 48 patients underwent a SST in whom aldosterone levels were measured using LC-MS/MS during the specified period. Thirteen patients were excluded from the analysis due to insufficient medical information or lack of follow-up, leaving 35 patients for inclusion in this study. The median age was 52 years (IQR: 43.0, 57.0); 71% were women, and 60% were White. The clinical characteristics of the patients are listed in Table 1.

Table 1.

Baseline Patient Characteristics at the Time of Screening of the Entire Cohort and by PA Status

Variables	All	No PA	Confirmed PA	P value
Number of patients	35	9	26
Age, y, median (IQR)	52.0 (43.0, 57.0)	43.0 (35.0, 53.0)	52.5 (49.0, 57.0)	0.100
Female sex, n (%)	25 (71)	8 (89)	17 (65)	0.420
Race, n (%)				0.018
White	21 (60)	9 (100)	12 (46)
Black	9 (26)	0 (0)	9 (35)
Asian	5 (14)	0 (0)	5 (19)
Hispanic ethnicity, n (%)	2 (6)	2 (22)	0 (0)	-
BMI, kg/m2, median (IQR)	30.5 (28.3, 35.0)	29.8 (28.3, 31.5)	30.6 (28.4, 37.4)	0.360
Clinical features, n (%)
Hypertension	34 (97)	8 (89)	26 (100)	0.085
Hypokalemia	25 (71)	3 (33)	22 (85)	0.003
Diabetes	9 (26)	1 (11)	8 (31)	0.240
Hyperlipidemia	5 (14)	0 (0)	5 (19)	-
Obstructive sleep apnea	2 (6)	0 (0)	2 (8)	-
Chronic kidney disease	3 (9)	0 (0)	3 (12)	-
Age at diagnosis of hypertension, y, median (IQR)	40.0 (33.0, 44.0)	38.5 (19.5, 47.0)	40.0 (35.0, 44.0)	0.640
Renin (ng/ml/h), median (IQR)	0.22 (0.16, 0.58)	1.02 (0.58, 1.37)	0.19 (0.16, 0.27)	<0.001
Aldosterone (ng/dl), median (IQR)	19.0 (14.0, 33.1)	35.3 (19.9, 36.4)	16.9 (14.0, 26.4)	0.100
Potassium (mmol/l), median (IQR)	3.9 (3.4, 4.3)	4.4 (4.4, 4.6)	3.6 (3.2, 4.0)	<0.001
Aldosterone-renin ratio, median (IQR)	75.5 (32.4, 132.0)	34.6 (14.4, 39.1)	90.2 (43.7, 133.3)	0.010

Abbreviations: BMI = body mass index; PA = primary aldosteronism.

Data are presented as number (%) or median (IQR).

P values were compared between 2 groups (no PA and confirmed PA). Significant at P < 0.05.

Clinical Characteristics

Out of the 35 patients, the diagnosis of PA was confirmed in 26 patients. In the remaining 9 patients, a diagnosis of overt PA was not established (no PA). No statistically significant differences between the 2 groups were found in age (43.0 vs 52.5, P = 0.10), body mass index (29.8 vs 30.6 kg/m², P = 0.36), age of diagnosis of hypertension (38.5 vs 40.0, P = 0.64), or other comorbidities included (Table 1). Except for 1 patient in the no PA group who was screened due to an adrenal incidentaloma, all patients had hypertension. Patients with PA (confirmed PA) were more likely to have a history of hypokalemia (85% vs 33%, P = 0.003, Table 1).

Biochemical Characteristics

At the time of initial screening (not SST), patients with confirmed PA had a median PRA that was significantly lower than the no PA group (0.19 vs 1.02 ng/ml/h, P < 0.001). The median aldosterone levels on screening were higher in the no PA group, but the difference was not statistically significant (35.3 vs 16.9 ng/dl, P = 0.10). Consequently, aldosterone-renin ratios were significantly higher in the confirmed PA group compared to the no PA group (90.2 vs 34.6 ng/dl per ng/ml/h, P = 0.007). Potassium levels were significantly lower in the confirmed PA group (3.6 vs 4.4 mmol/l, P < 0.01). More patients had adrenal nodules in the confirmed PA group than in the no PA (73.1 vs 33.3%, P = 0.033). Of those with adrenal nodules, a total of 5 patients had abnormal 1 mg dexamethasone suppression test (cortisol between ≥1.8-4.9 ug/dl). One in the no PA group and 4 in the confirmed PA group.

Saline Suppression Test

At baseline during the SST, patients with confirmed PA had lower median PRA (0.17 vs 0.47 ng/ml/h, P = 0.022) and higher aldosterone levels (16.0 ng/dl [IQR: 14.0, 26.0] vs 11.0 ng/dl [IQR: 6.0, 13.0], P = 0.016). The median aldosterone levels postsaline infusion in the confirmed PA group was 11.5 ng/dl (IQR: 8.0, 18.0, range: 4.0-46.0). None of the patients in the no PA group had an aldosterone level >3.0 ng/dl (median: 1.0 ng/dl, IQR: 1.0, 2.0, range: 1.0-3.0 ng/dl) (Fig. and Table 2). The median percentage reduction in aldosterone from baseline to postsaline infusion in the confirmed PA and no PA groups was −28.3% and −83.3% (P < 0.001), respectively (Table 2).

Fig.

Box and whisker plots demonstrating aldosterone levels in groups with and without PA at baseline and postsaline infusion. Circles represent outliers. Microsoft Excel v16.81 (2024). PA = primary aldosteronism.

Table 2.

Individual Patient Clinical Characteristics and Saline Suppression Test Data

Patient characteristics							Saline suppression test				Treatment
No.	Age	Sex	BMI	No. of BP medsd	Hypokalemiad	Adrenal nodule	PRAd	Aldosteroned		% Change
							Baseline	Baseline	4 H
No PA
1	22	F	31.5	0	-	-	2.53e	61.0	1.0	−98.4	Medical
2	70	F	25.3	2	-	+	0.15	11.0	1.0	−90.9	Medical
3	53	F	30.7	2	+	-	0.31	6.0	1.0	−83.3	Medical
4	43	F	29.8	3	-	-	0.58	5.0	1.0	−80.0	Medical
5	40	F	21.7	1	+	-	0.37	4.0	1.0	−75.0	Medical
6	48	F	28.3	1	-	+	1.35	14.0	2.0	−85.7	Medical
7	35	F	29.7	1	-	-	1.18	13.0	2.0	−84.6	Medical
8	26	F	33.0	1	+	-	3.10	11.0	3.0	−72.7	Medical
9	64	M	33.5	0	-	+	0.15	6.0	3.0	−50.0	Surgicalb
a	43	89%	29.8	1	33%	33.3%	0.47	11	1.0	−83.3
Confirmed PA
1	50	F	38.7	2	+	+	0.17	14.0	4.0	−71.4	Surgical
2	51	M	25.1	1	+	-	0.14	9.0	5.0	−44.4	Medical
3	58	F	39.1	3	+	+	0.22	19.0	6.0	−68.4	Surgical
4	70	F	31.0	2	+	+	0.07	24.0	7.0	−70.8	Medical
5	53	M	42.5	3	-	-	0.24	14.0	7.0	−50.0	Medical
6	43	F	42.0	1	-	+	0.19e	19.0	8.0	−57.9	Surgical
7	49	F	22.3	1	+	-	0.33	15.0	8.0	−46.7	Medical
8	62	F	25.3	1	+	+	0.50	7.0	8.0	+14.3	Medical
9	52	M	41.3	2	+	-	0.73	13.0	9.0	−30.8	Surgical
10	49	M	23.7	3	+	+	0.12	10.0	9.0	−10.0	Medical
11	52	M	28.4	1	+	-	0.17	55.2	10.0	−81.9	Medical
12	53	F	30.4	1	+	+	0.10	24.0	10.0	−58.3	Surgical
13	55	F	39.8	2	+	+	0.20	7.0	11.0	+57.1	Surgical
14	57	F	30.8	3	-	-	0.13	10.0	12.0	+20.0	Surgical
15	45	F	24.6	0	+	+	0.08e	10.0	12.0	+20.0	Surgical
16	54	F	36.1	1	+	+	0.16	17.0	13.0	−23.5	Medical
17	57	M	30.3	1	+	+	1.50	15.0	15.0	0.00	Surgical
18	36	F	29.0	1	+	+	0.48	15.0	15.0	0.00	Surgical
19	57	F	29.0	2	+	+	0.12	46.0	16.0	−65.2	Surgical
20	50	M	28.5	3	+	+	0.69	39.0	18.0	−53.8	Medical
21	53	F	24.0	2	-	+	0.08	21.0	19.0	−9.5	Surgical
22	63	M	37.4	3	+	+	0.25e	30.0	20.0	−33.3	Surgical
23	40	F	34.8	2	+	+	0.32e	27.0	20.0	−25.9	Surgical
24	41	F	31.0	2	+	-	0.07	18.0	22.0	+22.2	Medical
25	66	F	35.0	4	+	+	0.22e	31.0	23.0	−25.8	Medical
26	52	M	30.5	4	+	+	0.15e	14.0	46.0	+228.6	Surgical
a	52.5	65%	30.6	2	84.6%	73.1%	0.17	16.0	11.5	−28.3	c

Abbreviations: BMI = body mass index; BP = blood pressure; F = female; M = male; PA = primary aldosteronism; PRA = plasma renin activity.

^aRepresents median, and in the sex category, it is the percentage of females.

^bRepresents negative CYP11B2 immunostaining.

^cRepresents a total of 15 surgical and 11 medically treated patients.

^dNo. of BP meds: number of blood pressure medications at the time of the saline suppression test. Hypokalemia: previous or current history of hypokalemia. Hypokalemia is defined as serum potassium <3.5 mmol/l. Aldosterone in ng/dl, PRA in ng/ml/h. PRA baseline: plasma renin activity on the day of the saline suppression test.

^eBaseline PRA values were not available for some patients on the day of saline suppression test. For these patients we have included the screening PRA level (not included in the calculations presented in this table).

The median baseline BP in the no PA and confirmed PA groups was 129/75 mmHg (IQR: 126/71-139/78) and 144/80 mmHg (IQR: 137/74-167/87), respectively. The median peak BP in the no PA group and the confirmed PA groups were 147/80 mmHg and 159/86 mmHg, respectively. No symptomatic hypertensive crisis or sustained hypertension was reported. Two patients had transient hypertension spikes that were treated with oral hydralazine and returned to baseline within the duration of the test.

In the confirmed PA group, 15 patients underwent adrenalectomy, and 11 were treated with an MRA. In the no PA group, 1 patient (patient 9 in Table 2) underwent adrenalectomy due to the size of the adrenal nodule. Pathology reported an adrenal cortical neoplasm of 7.7 cm (Modified-Weiss score 2) and had a nonpathologic CYP11B2 immunostaining. It is important to note that in the no PA group, patient 1 in Table 2, had a markedly elevated baseline aldosterone of 61 ng/dl, which suppressed to 1.0 ng/dl after saline. At the time, this patient was using drospirenone as a contraceptive, which is known to have MRA properties.

Discussion

In this study, we describe our experience with measurement of aldosterone levels tested by LC-MS/MS in a reference laboratory during the SST in real-world practice. We observed lower postsaline infusion aldosterone levels associated with PA than the level suggested in the 2016 Endocrine Society guidelines (>10 ng/dl [277.4 pmol/l]) or the historically used criteria >5-10 ng/dl (138.7-277.4 pmol/l).⁶ In this group of patients, the lowest postinfusion aldosterone concentration in the confirmed PA group was 4.0 ng/dl (111 pmol/l). In this patient, PA was confirmed with CYP11B2 immunohistochemistry reporting multiple aldosterone-producing micronodules and a postoperative day 1 aldosterone level of 2 ng/dl. In contrast, none of the patients in the no PA group had a postsaline aldosterone level >3.0 ng/dl (83 pmol/l). These results indicate that using an SST cutoff of >10 ng/dl would have resulted in missing the diagnosis of PA in 10 (of 35) patients, of whom 4 had surgically confirmed PA and achieved remission or significant clinical improvement. The results presented in this small cohort are highly relevant for the endocrinologist’s day-to-day practice, as there is the possibility of missing or delaying the diagnosis in a significant group of patients if using older cutoff values.

The effects of volume expansion on aldosterone have been described since the late 1950s, which led to the development of the SST in the early 1970s.15, 16, 17 The principle is that volume expansion leads to decreased renin and angiotensin II and therefore aldosterone concentrations. Initially, aldosterone levels were measured using radioimmunoassay. The immunoassays have significant cross-reactivity with other steroids, leading to falsely elevated aldosterone concentrations.¹⁸ In recent years, liquid chromatography has been used together with mass spectrometry (LC-MS/MS) to measure steroids with high precision and specificity. LC-MS/MS has demonstrated consistently lower aldosterone levels when compared to immunoassay, with aldosterone levels up to 86% lower.^18,19 Accordingly, it has been reported that during SST aldosterone levels are 36% lower at baseline and 37% to 56% lower at 4 hours when using LC-MS/MS compared to immunoassays.⁹ This difference between LC-MS/MS and immunoassays seems to be more pronounced at lower levels (<10 ng/dl [277.4 pmol/l]), where the discrepancy is highest.¹⁸

Our results are consistent with data from other groups that recognized lower aldosterone levels when using LC-MS/MS in different clinical scenarios during evaluation for PA, such as screening,²⁰ adrenal vein sampling,²¹ and during SST, with some experts recommending a diagnostic threshold of 5-6 ng/dl post-SST.^9,22 Others have described a cutoff value for the exclusion of PA after SST as low as 3 ng/dl (83 pmol/l).¹² These studies were primarily performed in controlled research settings, with laboratory-specific LC-MS/MS assays. Although interlaboratory and intermethod agreement for aldosterone by LC-MS/MS has been shown to be improved compared to immunoassay,^19,23,24 there are no reference methods or standard reference materials,^18,25 thus, cutoffs may not be interchangeable owing to laboratory methodology and populations studied. Use of an assay available at a commercial reference laboratory, such as that used in this study, can aid in applicability.¹⁸

In our sample, postsaline aldosterone levels of ≥4.0 ng/dl perfectly separated patients with and without confirmed PA. While receiver operating characteristic analysis yielded an optimal cutoff of 4.0 ng/dl with 100% sensitivity and specificity, these results should be interpreted with caution due to the small sample size and perfect separation in this limited cohort. Larger studies are needed to validate assay-specific results using commercial LC-MS/MS platforms. We acknowledge that PA is a continuum of dysregulated aldosterone production from clinically silent (ie, normotensive, normokalemic patients) with low renin and normal or low aldosterone levels to overt clinical phenotypes characterized by hypertension, hypokalemia, and suppressed renin with elevated aldosterone concentrations.^26,27 Additionally, nonsuppressible aldosterone levels have been observed along entire spectrum of PA.²⁸ To add to the complexity of SST interpretation, there is high intraindividual and interindividual variability of aldosterone levels in PA.^20,21,29, 30, 31 Therefore, a one-time SST may not capture the dynamic nature of this process and the significant aldosterone variability. In the study by Buffolo et al,²² approximately 20% of individuals with a negative confirmatory test (SST or CCT) developed overt PA over the following 5 years. Accordingly, it is possible that the cutoffs in that study may need to be revisited, and some of the patients initially considered negative for PA may indeed have PA. Furthermore, another group has recently brought concerns about the value and high rates of false negative results with SST.³² Nevertheless, patients without established PA need to be monitored and have additional or repeat testing based on their clinical and biochemical characteristics.

Our study has several limitations. First, its retrospective design has implicit biases and limitations. Second, the sample size is relatively small. Larger prospective studies are needed to confirm our findings when using LC-MS/MS. In addition, most patients, particularly in the no PA group, were women, which limits generalizations but may also reflect the higher prevalence of PA in women or that women seek medical care and undergo more SST than men. Furthermore, there are no established guidelines for using a different postsaline aldosterone cutoff between different sexes. The patients in the no PA group were also about 9 years younger than in the confirmed PA group. Interestingly, our postsaline aldosterone levels did not overlap between the 2 groups (confirmed PA and no PA), which may be seen in a larger population. Third, there is no control group to better characterize aldosterone suppressibility during the SST in normal individuals using LC-MS/MS. However, the study represents real-life experience in a tertiary academic center using a commercially available aldosterone mass spectrometry assay. Fourth, we described patients managed surgically and medically together, and these populations may need to be considered individually, as unilateral and bilateral PA do not behave similarly and tend to have different genetic backgrounds. Nonetheless, the study adds to the limited amount of data in the literature on confirmatory tests outside research scenarios in the literature.

Conclusions

Using an LC-MS/MS aldosterone assay from a commercial reference laboratory, we report that saline suppression in patients with confirmed PA can show aldosterone levels as low as 4.0 ng/dl. This is much lower than the Endocrine Society’s suggested cutoff of 10 ng/dl and lower than the traditionally used aldosterone cutoffs of 5-10 ng/dl using immunoassays during the SST. These data can help clinicians avoid missing patients with PA and make better clinical decisions. We acknowledge that there is a need for prospective and larger studies to confirm these findings.

Ethics Approval

This study was reviewed and approved by the Johns Hopkins University Institutional Review Board (IRB00415476).

Disclosure

The authors have no conflicts of interest to disclose.