Case detection in primary aldosteronism: high-diagnostic value of the aldosterone-to-renin ratio when performed under standardized conditions

Screening for Primary Aldosteronism by Mass Spectrometry Versus Immunoassay Measurements of Aldosterone: A Prospective Within-Patient Study

BACKGROUND

Measurements of aldosterone by mass spectrometry are more accurate and less prone to interferences than immunoassay measurements, and may produce a more accurate aldosterone:renin ratio (ARR) when screening for primary aldosteronism (PA).

METHODS

Differences in diagnostic performance of the ARR using mass spectrometry vs immunoassay measurements of aldosterone were examined in 710 patients screened for PA. PA was confirmed in 153 patients and excluded in 451 others. Disease classifications were not achieved in 106 patients. Areas under receiver-operating characteristic curves (AUROC) and other measures were used to compare diagnostic performance.

RESULTS

Mass spectrometry-based measurements yielded lower plasma aldosterone concentrations than immunoassay measurements. For the ARR based on immunoassay measurements of aldosterone, AUROCs were slightly lower (P = 0.018) than those using mass spectrometry measurements (0.895 vs 0.906). The cutoff for the ARR to reach a sensitivity of 95% was 30 and 21.5 pmol/mU by respective immunoassay and mass spectrometry-based measurements, which corresponded to specificities of 57% for both. With data restricted to patients with unilateral PA, diagnostic sensitivities of 94% with specificities >81% could be achieved at cutoffs of 68 and 52 pmol/mU for respective immunoassay and mass spectrometry measurements.

CONCLUSIONS

Mass spectrometry-based measurements of aldosterone for the ARR provide no clear diagnostic advantage over immunoassay-based measurements. Both approaches offer limited diagnostic accuracy for the ARR as a screening test. One solution is to employ the higher cutoffs to triage patients likely to have unilateral PA for further tests and possible adrenalectomy, while using the lower cutoffs to identify others for targeted medical therapy.German Clinical Trials Register ID: DRKS00017084.

Underdiagnosis of Primary Aldosteronism: A Review of Screening and Detection

A clinical condition may be missed due to its higher-than-recognized prevalence or inadequate diagnostic screening. Both factors apply to primary aldosteronism, which is woefully underdiagnosed as a cause of hypertension and end-organ damage. Screening tests should be strongly considered for diseases that pose significant morbidity or mortality if left untreated, that have a high prevalence, and that have treatments that lead to improvement or cure. In this review we present the evidence for each of these points. We outline studies that estimate the prevalence of primary aldosteronism in different at-risk populations and how its recognition has changed over time. We also evaluate myriad studies of screening rates for primary aldosteronism and what factors do and do not influence current screening practices. We discuss the ideal conditions for screening, measuring the aldosterone to renin ratio in different populations that use plasma renin activity or direct renin concentration, and the steps for diagnostic workup of primary aldosteronism. Finally, we conclude with potential strategies to implement higher rates of screening and diagnosis of this common, consequential, and treatable disease.

Exclusion Tests in Unilateral Primary Aldosteronism (ExcluPA) Study

CONTEXT

Determining the diagnostic accuracy of "exclusion" tests for primary aldosteronism (PA) compared to the aldosterone to renin ratio (ARR) is fundamental to avoid invasive subtyping in false-positive patients at screening.

OBJECTIVE

To assess the accuracy of exclusion tests for PA using the diagnosis of unilateral PA as reference.

METHODS

PubMed, EMBASE, Web of Science, and Cochrane Library databases were searched for studies published from January 1, 1970, to December 31, 2021, meeting tight quality criteria. Data were extracted following the PRISMA methodology. We performed a two-stage meta-analysis that entailed an exploratory and a validation phase based on a "golden" or "gold" diagnostic standard, respectively. Pooled specificity, negative likelihood ratio, diagnostic odds ratio, and summary area under the ROC curve (sAUROC) were calculated to analyze the accuracy of exclusion tests.

RESULTS

A meta-analysis of 31 datasets comprising a total of 4242 patients fulfilling the predefined inclusion criteria found that pooled accuracy estimates (sAUROC) did not differ between the ARR (0.95; 95% CI, 0.92-0.98), the captopril challenge test (CCT) (0.92; 95% CI, 0.88-0.97), and the saline infusion test (SIT) (0.96; 95% CI, 0.94-0.99). Solid information could not be obtained for the fludrocortisone suppression test and the furosemide upright test, which were assessed in only 1 study each.

CONCLUSION

The apparently high diagnostic accuracy of the CCT and the SIT was due to the selection of patients with an elevated ARR and thus a high pretest probability of unilateral PA; however, neither test furnished a diagnostic gain over the ARR. Therefore, the systematic use of these exclusion tests in clinical practice is not justified by available evidence.

The Saline Infusion Test for Primary Aldosteronism: Implications of Immunoassay Inaccuracy

CONTEXT

Diagnosis of primary aldosteronism (PA) for many patients depends on positive results for the saline infusion test (SIT). Plasma aldosterone is often measured by immunoassays, which can return inaccurate results.

OBJECTIVE

This study aimed to establish whether differences in aldosterone measurements by immunoassay versus mass spectrometry (MS) might impact confirmatory testing for PA.

METHODS

This study, involving 240 patients tested using the SIT at 5 tertiary care centers, assessed discordance between immunoassay and MS-based measurements of plasma aldosterone.

RESULTS

Plasma aldosterone measured by Liaison and iSYS immunoassays were respectively 86% and 58% higher than determined by MS. With an immunoassay-based SIT cutoff for aldosterone of 170 pmol/L, 78 and 162 patients had, respectivel, negative and positive results. All former patients had MS-based measurements of aldosterone < 117 pmol/L, below MS-based cutoffs of 162 pmol/L. Among the 162 patients with pathogenic SIT results, MS returned nonpathologic results in 62, including 32 under 117 pmol/L. Repeat measurements by an independent MS method confirmed nonpathogenic results in 53 patients with discordant results. Patients with discordant results showed a higher (P < 0.0001) prevalence of nonlateralized than lateralized adrenal aldosterone production than patients with concordant results (83% vs 28%). Among patients with nonlateralized aldosterone production, 66% had discordant results. Discordance was more prevalent for the Liaison than iSYS immunoassay (32% vs 16%; P = 0.0065) and was eliminated by plasma purification to remove interferents.

CONCLUSION

These findings raise concerns about the validity of immunoassay-based diagnosis of PA in over 60% of patients with presumed bilateral disease. We provide a simple solution to minimize immunoassay inaccuracy-associated misdiagnosis of PA.

Diagnostic value of aldosterone to renin ratio calculated by plasma renin activity or plasma renin concentration in primary aldosteronism

Background:

Since the diagnostic value of aldosterone to renin ratio (ARR) calculated by plasma renin concentration (PRC) or plasma renin activity (PRA) is still inconclusive, we conducted a meta-analysis by systematically reviewing relevant literature to explore the difference in the diagnostic efficacy of ARR calculated by PRC or PRA, so as to provide guidance for clinical diagnosis.

Methods:

We searched PubMed, Embase, and Cochrane Library from the establishment of the database to March 2021. We included studies that report the true positive, false positive, true negative, and false negative values for the diagnosis of primary aldosteronism, and we excluded duplicate publications, research without full text, incomplete information, or inability to conduct data extraction, animal experiments, reviews, and systematic reviews. STATA 15.1 was used to analyze the data.

Results:

The pooled results showed that ARR (plasma aldosterone concentration [PAC]/PRC) had a sensitivity of 0.82 (95% confidence interval [CI]: 0.78–0.86), a specificity of 0.94 (95% CI: 0.92–0.95), a positive-likelihood ratio (LR) of 12.77 (95% CI: 7.04–23.73), a negative LR of 0.11 (95% CI: 0.07–0.17), and symmetric area under the curve (SAUC) of 0.982, respectively. Furthermore, the diagnostic odds ratio (DOR) of ARR (PAC/PRC) was 180.21. Additionally, the pooled results showed that ARR (PAC/PRA) had a sensitivity of 0.91 (95% CI: 0.86–0.95), a specificity of 0.91 (95% CI: 0.90–0.93), a positive LR of 7.30 (95% CI: 2.99–17.99), a negative LR of 0.10 (95% CI: 0.04–0.26), and SAUC of 0.976, respectively. The DOR of ARR (PAC/PRA) was 155.52. Additionally, we conducted a subgroup analysis for the different thresholds (<35 or ≥35) of PAC/PRC. The results showed that the DOR of the cut-off ≥35 groups was higher than the cut-off <35 groups (DOR = 340.15, 95% CI: 38.32–3019.66; DOR = 116.40, 95% CI = 23.28–581.92).

Conclusions:

The research results suggest that the determination of ARR (PAC/PRC) and ARR (PAC/PRA) was all effective screening tools for PA. The diagnostic accuracy and diagnostic value of ARR (PAC/PRC) are higher than ARR (PAC/PRA). In addition, within a certain range, the higher the threshold, the better the diagnostic value.

Performance of the Aldosterone to Renin Ratio as a Screening Test for Primary Aldosteronism

CONTEXT

The aldosterone to renin ratio (ARR) is the guideline-recommended screening test for primary aldosteronism. However, there are limited data in regard to the diagnostic performance of the ARR.

OBJECTIVE

To evaluate the sensitivity and specificity of the ARR as a screening test for primary aldosteronism.

METHODS

We searched the MEDLINE, Embase, and Cochrane databases until February 2020. Observational studies assessing ARR diagnostic performance as a screening test for primary aldosteronism were selected. To limit verification bias, only studies where dynamic confirmatory testing was implemented as a reference standard regardless of the ARR result were included. Study-level data were extracted and risk of bias and applicability were assessed using the QUADAS-2 tool.

RESULTS

Ten studies, involving a total of 4110 participants, were included. Potential risk of bias related to patient selection was common and present in half of the included studies. The population base, ARR positivity threshold, laboratory assay, and reference standard for confirmatory testing varied substantially between studies. The reported ARR sensitivity and specificity varied widely with sensitivity ranging from 10% to 100% and specificity ranging from 70% to 100%. Notably, 3 of the 10 studies reported an ARR sensitivity of <50%, suggesting a limited ability of the ARR to adequately identify patients with primary aldosteronism.

CONCLUSIONS

ARR performance varied widely based on patient population and diagnostic criteria, especially with respect to sensitivity. Therefore, no single ARR threshold for interpretation could be recommended. Limitations in accuracy and reliability of the ARR must be recognized in order to appropriately inform clinical decision-making.

Adrenalectomy for Primary Aldosteronism: Significant Variability in Work-Up Strategies and Low Guideline Adherence in Worldwide Daily Clinical Practice

BACKGROUND

Various diagnostic tests are available to establish the primary aldosteronism (PA) diagnosis and to determine the disease laterality. Combined with the controversies in the literature, unawareness of guidelines and technical demands and high costs of some of these diagnostics, this could lead to significant differences in work-up strategies worldwide. Therefore, we investigated the work-up before surgery for PA in daily clinical practice within a multicenter study.

METHODS

Patients who underwent unilateral adrenalectomy for PA within 16 centers in Europe, Canada, Australia and the USA between 2010 and 2016 were included. We did not exclude patients based on the performed diagnostic tests during work-up to make our data representative for current clinical practice. Adherence to the Endocrine Society Guideline and variables associated with not performing adrenal venous sampling (AVS) were analyzed.

RESULTS

In total, 435 patients were eligible. An aldosterone-to-renin ratio, confirmatory test, computed tomography (CT), magnetic resonance imaging and AVS were performed in 82.9%, 32.9%, 86.9%, 17.0% and 65.3% of patients, respectively. A complete work-up, as recommended by the guideline, was performed in 13.1% of patients. Bilateral disease or normal adrenal anatomy on CT (OR 16.19; CI 3.50-74.99), smaller tumor size on CT (OR 0.06; CI 0.04-0.08) and presence of hypokalemia (OR 2.00; CI 1.19-3.32) were independently associated with performing AVS.

CONCLUSIONS

This study is the first to examine the daily clinical practice work-up of PA within a worldwide cohort of surgical patients. The results demonstrate significant variability in work-up strategies and low adherence to The Endocrine Society guideline.

Confounders of the aldosterone-to-renin ratio when used as a screening test in hypertensive patients: A critical analysis of the literature

The aldosterone‐to‐renin ratio (ARR) is a common screening test for primary aldosteronism in hypertensives. However, there are many factors which could confound the ARR test result and reduce the accuracy of this test. The present review's objective is to identify these factors and to describe to what extent they affect the ARR. Our analysis revealed that sex, age, posture, and sodium‐intake influence the ARR, whereas assay techniques do not. Race and body mass index have an uncertain effect on the ARR. We conclude that several factors can affect the ARR. Not taking these factors into account could lead to misinterpretation of the ARR.

Development of a clinical decision tool to reduce diagnostic testing for primary aldosteronism in patients with difficult-to-control hypertension

BACKGROUND

Satisfactory tools to preclude low-risk patients from intensive diagnostic testing for primary aldosteronism (PA) are lacking. Therefore, we aimed to develop a decision tool to determine which patients with difficult-to-control hypertension have a low probability of PA, thereby limiting the exposure to invasive testing while at the same time increasing the efficiency of testing in the remaining patients.

METHODS

Data from consecutive patients with difficult-to-control hypertension, analysed through a standardized diagnostic protocol between January 2010 and October 2017 (n = 824), were included in this cross-sectional study. PA was diagnosed by a combined approach: 1) elevated aldosterone-to-renin ratio (> 5.0 pmol/fmol/s), confirmed with 2) non-suppressible aldosterone after standardized saline infusion (≥280 pmol/L). Multivariable logistic regression analyses including seven pre-specified clinical variables (age, systolic blood pressure, serum potassium, potassium supplementation, serum sodium, eGFR and HbA1c) was performed. After correction for optimism, test reliability, discriminative performance and test characteristics were determined.

RESULTS

PA was diagnosed in 40 (4.9%) of 824 patients. Predicted probabilities of PA agreed well with observed frequencies and the c-statistic was 0.77 (95% confidence interval (95%CI) 0.70-0.83). Predicted probability cut-off values of 1.0-2.5% prevented unnecessary testing in 8-32% of the patients with difficult-to-control hypertension, carrying sensitivities of 0.98 (95%CI 0.96-0.99) and 0.92 (0.83-0.97), and negative predictive values of 0.99 (0.98-1.00) and 0.99 (0.97-0.99).

CONCLUSIONS

With a decision tool, based on seven easy-to-measure clinical variables, patients with a low probability of PA can be reliably selected and a considerable proportion of patients with difficult-to-control hypertension can be spared intensive diagnostic testing.

Diagnostic Accuracy of the Aldosterone-to-Active Renin Ratio for Detecting Primary Aldosteronism

Context

The aldosterone-to-active renin ratio (AARR) is the recommended screening test for primary aldosteronism (PA), but prospective study data on its sensitivity and specificity are sparse.

Objective

To investigate the diagnostic accuracy of the AARR for detecting PA.

Design

Prospective diagnostic accuracy study.

Setting

This study was conducted from February 2009 to August 2015 at the outpatient clinic of the Department of Endocrinology and Diabetology of the Medical University of Graz, Austria.

Participants

Four hundred patients with arterial hypertension who were referred to a tertiary care center for screening for endocrine hypertension.

Intervention

Participants had a determination of the AARR (index test) and a second AARR determination followed by a saline infusion test (SIT) after 2 to 6 weeks. PA was diagnosed in individuals with any AARR ≥3.7 ng/dL/µU/mL [including a plasma aldosterone concentration (PAC) of ≥9 ng/dL] who had a PAC ≥10 ng/dL after the SIT. We did not substantially alter antihypertensive drug intake.

Main Outcome Measures

Primary outcome was the receiver-operating characteristic (ROC) curve of the AARR in diagnosing PA.

Results

A total of 382 participants were eligible for analyses; PA was diagnosed in 18 (4.7%) patients. The area under the ROC curve of the AARR in detecting PA was 0.973 (95% CI, 0.956 to 0.990). Sensitivity and specificity for a positive AARR in diagnosing PA were 100% (95% CI, 81.5% to 100.0%) and 89.6% (95% CI, 86.0% to 92.5%), respectively.

Conclusions

The AARR has good diagnostic accuracy for detecting PA.