A renin-ssance in primary aldosteronism testing: obstacles and opportunities for screening, diagnosis, and management

Poor comparability of plasma renin activity measurement in determining patient samples: the status quo and recommendations for harmonization

OBJECTIVES

This study aims to investigate and update the consistency and comparability of plasma renin activity (PRA) assays in measuring clinical samples. The contributions of recalibration, blank subtraction, and incubation strategies to interchangeability were also explored.

METHODS

Five different laboratories were evaluated using forty-six individual plasma samples, including four liquid chromatography-tandem mass spectrometry (LC‒MS/MS) assays and one chemiluminescence immunoassay (CLIA). Spearman correlation coefficient (R), Passing-Bablok regression, and Bland‒Altman plot analyses were used to evaluate the consistency among assays. Consistency before and after recalibration, blank subtraction, and incubation strategy unification was compared.

RESULTS

A good correlation was observed among all assays (R>0.93). None of the samples measured by all assays showed coefficient variation (CV) <10 %, and 37 % of samples showed overall CVs >20 %. The 95 % confidence intervals (CIs) for slopes did not contain 1 for most assay pairs. Large relative biases (-85.1-104.2 %) were found, and 76 % (52-93 %) of samples had unacceptable biases. Recalibration reduced the calibration bias. Ignoring blank subtraction improved the comparability across all assays while unifying incubation did not.

CONCLUSIONS

The interchangeability of PRA measurement was unsatisfying. Harmonization on calibrator and ignoring blank were recommended. Unifying incubation strategy was unnecessary.

Aldosterone, Renin, and Aldosterone-to-Renin Ratio Variability in Screening for Primary Aldosteronism

CONTEXT

The plasma aldosterone concentration (PAC), renin, and aldosterone-to-renin ratio (ARR) are used to screen for primary aldosteronism (PA). Substantial intra-individual variability of PAC and ARR using plasma renin activity in the context of usual antihypertensive therapy has been described, but there is no data on ARR variability calculated using direct renin concentration (DRC).

OBJECTIVE

To describe the intra-individual variability of PAC, DRC, and ARR in the absence of interfering medications in patients with and without PA.

DESIGN

Retrospective cohort study.

PATIENTS

Hypertensive patients referred for investigation of PA, with at least 2 ARR measurements while off interfering medications.

SETTING

Endocrine hypertension service of a tertiary center, from May 2017 to July 2021.

MAIN OUTCOME MEASURES

PAC, DRC, and ARR variability was calculated as coefficient of variation (CV) and percent difference (PD).

RESULTS

Analysis of 223 patients (55% female, median age 52 years), including 162 with confirmed PA, demonstrated high variability with a sample CV of 22-25% in the PAC and sample CV of 41% to 42% in the DRC and ARR in both the PA and non-PA groups. The degree of variability was substantially higher than the assays' analytical CV. Sixty-two patients (38%) with PA had at least one ARR below 70 pmol/L:mU/L (2.4 ng/dL:mU/L), a cut-off for first-line screening of PA.

CONCLUSIONS

Significant intra-individual variability in PAC, DRC, and hence ARR occurs in a large proportion of patients being investigated for PA. These findings support the need for at least 2 ARR before PA is excluded or further investigated.

Comparison of the Chemiluminescence Immunoassay LIAISON® with the Radioimmunoassay for Aldosterone and Renin Measurement

Determination of renin plasma levels is useful in the diagnosis of hypertension and in the therapeutic follow-up of hypertensive patients. Plasmatic concentration of renin decreases in patients with hypertension due to a primary hyperaldosteronism, contrary to renovascular hypertension where concentrations of renin and aldosterone are both elevated. Blood samples (serum, EDTA plasma) were analysed using two different chemiluminiscent methods CLIA LIAISON® and radioimmunoassay for aldosterone (IMMUNOTECH Beckman Coulter) and renin (Cisbio Bioassay) measurements were compared. We used both methods to ascertain the correlation between serum vs. EDTA plasma levels of aldosterone (RIA, CLIA) and renin (IRMA, CLIA) and to compare aldosterone to renin ratios for CLIA and for radioimmunoassay: serum aldosterone to plasma renin and plasma aldosterone to plasma renin. We compared serum aldosterone CLIA vs. RIA (rP=0.933, P&lt;0.001) and plasma renin determined using CLIA vs. IRMA (rP=0.965, P=0.062). Furthermore, we used both methods to establish the correlation between the serum vs. plasma levels of aldosterone: RIA (rP=0.980, P&lt;0.001); CLIA (rP=0.994, P=0.353) and serum vs. plasma levels of renin: IRMA (rP=0.948, P&lt;0.001); CLIA (rP=0.921, P=0.011). Aldosterone (serum, plasma) to plasmatic renin ratios for CLIA (rP=0.999, P=0.286) and for radioimmunoassay (rP=0.992, P=0.025). Our data demonstrate that renin and aldosterone concentrations obtained using CLIA correlate with renin and aldosterone concentrations using radioimmunoassay methods. Correlation coefficients of pair results ranged from 0.921 to 0.994. Aldosterone (serum, EDTA plasma) to plasmatic renin ratios are comparable and any of them can be used with no significant differences found.

Mineralocorticoid Dysfunction during Critical Illness: A Review of the Evidence

The recent demonstration of the significant reduction in mortality in patients with septic shock treated with adjunctive glucocorticoids combined with fludrocortisone and the effectiveness of angiotensin II in treating vasodilatory shock have renewed interest in the role of the mineralocorticoid axis in critical illness. Glucocorticoids have variable interactions at the mineralocorticoid receptor. Similarly, mineralocorticoid receptor-aldosterone interactions differ from mineralocorticoid receptor-glucocorticoid interactions and predicate receptor-ligand interactions that differ with respect to cellular effects. Hyperreninemic hypoaldosteronism or selective hypoaldosteronism, an impaired adrenal response to increasing renin levels, occurs in a subgroup of hemodynamically unstable critically ill patients. The suggestion is that there is a defect at the level of the adrenal zona glomerulosa associated with a high mortality rate that may represent an adaptive response aimed at increasing cortisol levels. Furthermore, cross-talk exists between angiotensin II and aldosterone, which needs to be considered when employing therapeutic strategies.

A case report of idiopathic hyperaldosteronism characterized by bilateral adrenal adenoma

RATIONALE

Primary aldosteronism (PA) comprises 2 main subtypes: unilateral aldosterone-producing adenoma (APA) and idiopathic hyperaldosteronism or named as bilateral adrenal hyperplasia (BAH). An accurate discrimination between APA and BAH is crucial because the former is treated with adrenalectomy (ADX) and the latter is primarily by aldosterone antagonists. We report a case of idiopathic hyperaldosteronism characterized by BAH.

PATIENT CONCERNS

A 46-year-old woman had experienced a paroxysmal elevation of blood pressure for the past 2 months, along with an intermittent headache and mild occipital swelling and pain.

DIAGNOSES

We performed clinical, laboratory, and imaging tests, as well as bilateral adrenal vein sampling (AVS) on this patient. Specifically, computed tomography scan and magnetic resonance imaging were used to characterize the properties of bilateral adrenal adenoma. Additionally, bilateral AVS was performed to distinguish unilateral from bilateral adrenal abnormality in this patient.

INTERVENTIONS

After oral administration of aldosterone antagonists, her blood pressure and potassium levels returned to normal ranges and her condition improved.

OUTCOMES

Following differential diagnosis, screening, functional tests, a variety of imaging studies, and bilateral adrenal vein sampling (AVS) typing, she was finally diagnosed with idiopathic hyperaldosteronism.

LESSONS

For PA patients with lack of typical hypertension and hypokalemia performance, early identification and accurate diagnosis are of great significance for improving the prognosis of BAH. AVS plays an important role in the classification of PA subtype, especially for the cases with bilateral lesions. In regard to patients with rare bilateral adrenocortical adenoma-type aldosteronism, AVS plays a key role in choosing the appropriate treatment regimen.

Primary Aldosteronism: Practical Approach to Diagnosis and Management

Primary aldosteronism (PA) is the most common form of secondary hypertension. In many cases, somatic mutations in ion channels and pumps within adrenal cells initiate the pathogenesis of PA, and this mechanism might explain why PA is so common and suggests that milder and evolving forms of PA must exist. Compared with primary hypertension, PA causes more end-organ damage and is associated with excess cardiovascular morbidity, including heart failure, stroke, nonfatal myocardial infarction, and atrial fibrillation. Screening is simple and readily available, and targeted therapy improves blood pressure control and mitigates cardiovascular morbidity. Despite these imperatives, screening rates for PA are low, and mineralocorticoid-receptor antagonists are underused for hypertension treatment. After the evidence for the prevalence of PA and its associated cardiovascular morbidity is summarized, a practical approach to PA screening, referral, and management is described. All physicians who treat hypertension should routinely screen appropriate patients for PA.

Clinical biomarker innovation: when is it worthwhile?

Background

Choosing which biomarker tests to select for further research and development is not only a matter of diagnostic accuracy, but also of the clinical and monetary benefits downstream. Early health economic modeling provides tools to assess the potential effects of biomarker innovation and support decision-making.

Methods

We applied early health economic modeling to the case of diagnosing primary aldosteronism in patients with resistant hypertension. We simulated a cohort of patients using a Markov cohort state-transition model. Using the headroom method, we compared the currently used aldosterone-to-renin ratio to a hypothetical new test with perfect diagnostic properties to determine the headroom based on quality-adjusted life-years (QALYs) and costs, followed by threshold analyses to determine the minimal diagnostic accuracy for a cost-effective product.

Results

Our model indicated that a perfect diagnostic test would yield 0.027 QALYs and increase costs by €43 per patient. At a cost-effectiveness threshold of €20,000 per QALY, the maximum price for this perfect test to be cost-effective is €498 (95% confidence interval [CI]: €275–€808). The value of the perfect test was most strongly influenced by the sensitivity of the current biomarker test. Threshold analysis showed the novel test needs a sensitivity of at least 0.9 and a specificity of at least 0.7 to be cost-effective.

Conclusions

Our model-based approach evaluated the added value of a clinical biomarker innovation, prior to extensive investment in development, clinical studies and implementation. We conclude that early health economic modeling can be a valuable tool when prioritizing biomarker innovations in the laboratory.

The aldosterone to renin ratio in the diagnosis of primary aldosteronism: Promises and challenges

The complexity of evaluating patients for secondary treatable causes of hypertension is underappreciated. Primary aldosteronism (PA) is the most prevalent cause of secondary hypertension (3%-32% of hypertensive patients). The recent endocrine society clinical practice guideline (ESCPG), "The Management of Primary Aldosteronism: Case Detection, Diagnosis, and Treatment", differs from the previous version in the explicit recognition of PA as a major public health issue. Despite this, PA is underdiagnosed. The guidelines call on physicians to substantially ramp up the screening of hypertensive patients at risk of PA. Further, it recommends the plasma aldosterone to renin ratio (ARR), as the test of choice for screening for PA. However, the ARR is a highly variable test with reported diagnostic sensitivities and specificities ranging from 66% to 100% and 61% to 100%, respectively. Variability of the ARR can be attributed to the high degree of within-subject variation, differences in sampling protocols, laboratory assays, reporting units, the effect of medications and the population characteristics used to establish the decision thresholds. These factors render the possibility of false positive and false negative results-which have the potential to adversely impact patients. The limitations and caveats to the use of the ARR necessitate an effective clinic-laboratory interface, with specialist physician and clinical scientist collaboration for ARR result interpretation. Improvement in the diagnostic sensitivity and specificity of the ARR is predicated on harmonisation of pretesting patient preparation criteria, knowledge of the analytical methods used to derive the ratio and the method-specific threshold for PA.

Is the plasma aldosterone-to-renin ratio associated with blood pressure response to treatment in general practice?

BACKGROUND

Individualized antihypertensive treatment based on specific biomarkers such as renin may lead to more effective blood pressure control in patients with newly diagnosed essential hypertension. Recent studies suggested that the plasma aldosterone-to-renin ratio (ARR) may also be a candidate predictor for this purpose.

OBJECTIVE

To assess whether the ARR is associated with the blood pressure response to antihypertensive treatment in patients with newly diagnosed hypertension.

METHODS

In this prospective cohort study in primary care, we determined the ARR in patients with newly diagnosed hypertension prior to starting treatment. Treatment was categorized in five groups: no medication, use of angiotensin-converting-enzyme inhibitor or angiotensin receptor blocker, use of calcium channel blocker, use of diuretic, or use of beta blocker. We examined the relation between the ARR and blood pressure response within 1 year of treatment, taking into account the type of antihypertensive treatment and adjusting for gender, age, baseline blood pressure, and comorbidity.

RESULTS

Out of 304 patients, we used 947 measurements (727 no medication, 220 medication) for analysis. There was no association between the ARR and the response in blood pressure, and this applied to each treatment group. Target blood pressure, defined as systolic blood pressure <140 mmHg, was reached in 31% of patients. There was no association between the ARR and reaching target blood pressure (OR 1.002, 95% CI 0.983-1.022).

CONCLUSION

The ARR is not associated with the response in blood pressure within 1 year of antihypertensive treatment in primary care.

Postmenopausal osteoporosis is associated with elevated aldosterone/renin ratio

Plasma aldosterone/renin ratio (ARR) is a useful method for primary aldosteronism (PA) screening. However some confounders, such as medications and dietary, affect plasma renin and aldosterone levels, resulting in false-negative or -positive plasma ARR. This study investigated the association between postmenopausal osteoporosis (PMO) and plasma ARR. Bone mineral density (BMD) was measured by dual-energy X-ray-absorptiometry (DXA) in 324 normotensive postmenopausal women. Based on clinical characteristics and BMD, 186 and 96 subjects were diagnosed as PMO and osteopenia respectively, and the remaining 42 subjects were grouped as normal BMD. Plasma aldosterone concentration (PAC), plasma renin concentration (PRC), parathyroid hormone (PTH), bone alkaline phosphatase (BALP) and 25-Hydroxyvitamin D(25-(OH)D) were determined. Subjects with PMO showed significantly higher levels of PAC (121.0 ± 78.8 vs. 81.8 ± 71.5 pg/ml, p < 0.01 and 121.0 ± 78.8 vs. 91.7 ± 56.2 pg/ml, p < 0.01) and ARR (32.0 ± 53.6 vs. 9.0 ± 9.3 pg/μU, p < 0.01 and 32.0 ± 53.6 vs. 16.3 ± 32.1 pg/μU, p < 0.01) compared to women with normal BMD and osteopenia, respectively. Using ARR ≥ 37.0 pg/μU as the cutoff for positive screening, more false-positive was found in the PMO group when compared to the normal BMD group (24 vs. 2%) and osteopenia group (24 vs. 7%), respectively. PAC was negatively associated with lumbar spine BMD T-score (r = -0.239, p < 0.001), femur neck BMD T-score (r = -0.234, p < 0.001) and total hip BMD T-score (r = -0.228, p < 0.001). PTH was positively associated with PAC (r = 0.119, p < 0.05) and ARR (r = 0.136, p < 0.05). PAC and ARR are elevated in women with PMO, which might increase the risk of false-positive for case detection of PA.

The Low-Renin Hypertension Phenotype: Genetics and the Role of the Mineralocorticoid Receptor

A substantial proportion of patients with hypertension have a low or suppressed renin. This phenotype of low-renin hypertension (LRH) may be the manifestation of inherited genetic syndromes, acquired somatic mutations, or environmental exposures. Activation of the mineralocorticoid receptor is a common final mechanism for the development of LRH. Classically, the individual causes of LRH have been considered to be rare diseases; however, recent advances suggest that there are milder and "non-classical" variants of many LRH-inducing conditions. In this regard, our understanding of the underlying genetics and mechanisms accounting for LRH, and therefore, potentially the pathogenesis of a large subset of essential hypertension, is evolving. This review will discuss the potential causes of LRH, with a focus on implicated genetic mechanisms, the expanding recognition of non-classical variants of conditions that induce LRH, and the role of the mineralocorticoid receptor in determining this phenotype.

Prevalence of primary aldosteronism in primary care: a cross-sectional study

BACKGROUND

Primary aldosteronism (PA) is the most frequent cause of secondary hypertension. Reported prevalences of PA vary considerably because of a large heterogeneity in study methodology.

AIM

To examine the proportion of patients with PA among patients with newly diagnosed, never treated hypertension.

DESIGN AND SETTING

A cross-sectional study set in primary care.

METHOD

GPs measured aldosterone and renin in adult patients with newly diagnosed, never treated hypertension. Patients with elevated aldosterone-to-renin ratio and increased plasma aldosterone concentration underwent a saline infusion test to confirm or exclude PA. The source population was meticulously assessed to detect possible selection bias.

RESULTS

Of 3748 patients with newly diagnosed hypertension, 343 patients were screened for PA. In nine out of 74 patients with an elevated aldosterone-to-renin ratio and increased plasma aldosterone concentration the diagnosis of PA was confirmed by a saline infusion test, resulting in a prevalence of 2.6% (95% confidence interval = 1.4 to 4.9). All patients with PA were normokalaemic and 8 out of 9 patients had sustained blood pressure >150/100 mmHg. Screened patients were younger (P<0.001) or showed higher blood pressure (P<0.001) than non-screened patients.

CONCLUSION

In this study a prevalence of PA of 2.6% in a primary care setting was established, which is lower than estimates reported from other primary care studies so far. This study supports the screening strategy as recommended by the Endocrine Society Clinical Practice Guideline. The low proportion of screened patients (9.2%), of the large cohort of eligible patients, reflects the difficulty of conducting prevalence studies in primary care clinical practice.

Screening for primary aldosteronism using the newly developed IDS-iSYS® automated assay system

BACKGROUND

The recommended approach to screening for primary aldosteronism (PA) in at-risk populations is to determine the ratio of aldosterone concentration (serum (SAC)/plasma (PAC)) to renin measured in plasma as activity (PRA) or concentration (DRC). However, lack of assay standardisation mandates the need for method-specific decision thresholds and clinical validation in the local population.

AIM

The study objective was to establish method-specific aldosterone: renin ratio (ARR) cut-offs for PA in men and women using the IDS-iSYS® assay system (IDS plc).

METHODS

A prospective cohort study design was used. PAC and DRC were measured immunochemically in ethylenediamine-tetraacetic acid (EDTA) plasma on the IDS-iSYS® instrument.

RESULTS

A total of 437 subjects (218 men, 219 women) were recruited including: healthy normotensive volunteers (n=266) and women taking the oral contraceptive pill (OCP; n=15); patients with essential hypertension (EH; n=128); confirmed PA (n=16); adrenal cortical carcinoma (ACC; n=3); Addison's disease (AD; n=4) and phaeochromocytoma/paraganglioma (PPGL; n=5). In this population, an ARR cut-off at >37.4 pmol/mIU provided 100% diagnostic sensitivity, 96% specificity and positive likelihood ratio for PA of 23:1. When the ARR decision threshold was stratified according to gender, a cut-off of >26.1 pmol/mIU in men and >113.6 pmol/mIU in women resulted in diagnostic sensitivity and specificity of 100%.

CONCLUSION

This study demonstrates that decision thresholds for PA should not only be method-specific but also gender-specific. However, given the small number of PA patients (n=16), particularly women (n=4), further validation through a prospective study with a larger PA cohort is required before the thresholds presented here could be recommended for routine clinical use.

Dietary Sodium Restriction Increases the Risk of Misinterpreting Mild Cases of Primary Aldosteronism

CONTEXT

The aldosterone to renin ratio (ARR) is recommended to screen for primary aldosteronism (PA).

OBJECTIVE

To evaluate whether dietary sodium restriction results in misinterpretation of PA screening.

PARTICIPANTS

Untreated hypertensives with ARR more than 20 on a high dietary sodium intake (HS) were also evaluated on a low dietary sodium intake (LS) (n = 241). Positive screening for PA was defined as: plasma renin activity (PRA) less than or equal to 1.0 ng/mL · h with serum aldosterone more than or equal to 6 ng/dL. PA was confirmed by a 24-hour urinary aldosterone excretion more than or equal to 12 mcg with urinary sodium more than 200 mmol.

RESULTS

Only 33% (79/241) of participants with an ARR more than 20 had a positive PA screen on HS. On LS, 56% (44/79) of these participants no longer met criteria for positive PA screening. When compared with participants with positive PA screening on both diets, participants with a positive screen on HS but negative on LS exhibited a significantly higher PRA on both diets. Remarkably, of the 48/79 participants who had PA confirmed, 52% had negative PA screening on LS. The distinguishing feature of these participants with "discordant" screening results was a larger rise in PRA on LS resulting in normalization of the ARR and higher Caucasian race prevalence.

CONCLUSIONS

Sodium restriction is recommended in hypertension; however, it can significantly raise PRA, normalize the ARR, and result in false interpretation of PA screening. Milder phenotypes of PA, where PRA is not as suppressed, are most susceptible to dietary sodium influences on renin and ARR. Optimal screening for PA should occur under conditions of HS.

Mass Spectrometry-Based Adrenal and Peripheral Venous Steroid Profiling for Subtyping Primary Aldosteronism

BACKGROUND

Differentiating patients with primary aldosteronism caused by aldosterone-producing adenomas (APAs) from those with bilateral adrenal hyperplasia (BAH), which is essential for choice of therapeutic intervention, relies on adrenal venous sampling (AVS)-based measurements of aldosterone and cortisol. We assessed the utility of LC-MS/MS-based steroid profiling to stratify patients with primary aldosteronism.

METHODS

Fifteen adrenal steroids were measured by LC-MS/MS in peripheral and adrenal venous plasma from AVS studies for 216 patients with primary aldosteronism at 3 tertiary referral centers. Ninety patients were diagnosed with BAH and 126 with APAs on the basis of immunoassay-derived adrenal venous aldosterone lateralization ratios.

RESULTS

Among 119 patients confirmed to have APAs at follow-up, LC-MS/MS-derived lateralization ratios of aldosterone normalized to cortisol, dehydroepiandrosterone, and androstenedione were all higher (P < 0.0001) than immunoassay-derived ratios. The hybrid steroids, 18-oxocortisol and 18-hydroxycortisol, also showed lateralized secretion in 76% and 35% of patients with APAs. Adrenal venous concentrations of glucocorticoids and androgens were bilaterally higher in patients with BAH than in those with APAs. Consequently, peripheral plasma concentrations of 18-oxocortisol were 8.5-fold higher, whereas concentrations of cortisol, corticosterone, and dehydroepiandrosterone were lower in patients with APAs than in those with BAH. Correct classification of 80% of cases of APAs vs BAH was thereby possible by use of a combination of steroids in peripheral plasma.

CONCLUSIONS

LC-MS/MS-based steroid profiling during AVS achieves higher aldosterone lateralization ratios in patients with APAs than immunoassay. LC-MS/MS also enables multiple measures for discriminating unilateral from bilateral aldosterone excess, with potential use of peripheral plasma for subtype classification.