Aldosterone Assay Research Articles

A-056 Investigating Iodine Contrast Contamination in Cortisol and Aldosterone Samples

Abstract Background Primary aldosteronism (PA) is a condition characterized by hypertension resulting from excess secretion of aldosterone. PA caused by a unilateral aldosterone-producing adenoma can be treated with adrenalectomy but requires diagnosis by adrenal vein sampling (AVS). In this procedure, intravenous cosyntropin is administered to stimulate adrenal cortical secretion, followed by obtaining samples from the right and left adrenal veins and IVC. Laterization index is calculated by obtaining the aldosterone:cortisol ratio for each side, with a ratio cutoff ≥3 is used for confirmation. Iodinated contrast media facilitates visualization of catheter positioning during AVS and sometimes results in contamination of samples, evidenced by abnormal gel separator flotation (i.e. gel above plasma). This study had two aims: 1) to determine at what concentration contrast dye causes gel flotation and 2) discern whether contrast media interferes with our cortisol or aldosterone assays. Methods Gel flotation studies were performed by spiking pooled plasma samples with iohexol contrast media (Omnipaque 240, GE Healthcare) at concentrations ranging from 3%-10% v/v and aliquoting into fresh lithium heparin plasma separator tubes (BD, PSTs). Samples were then centrifuged and visually inspected for abnormal gel flotation. Contrast interference studies were performed using three pools of low (5 µg/dL), medium, (30 µg/dL), and high (55 µg/dL) cortisol concentrations. Sample pools were diluted with 20% contrast media or saline (control) and subsequently mixed at different ratios to create a range of dye concentrations (0.5%-18% v/v). Each mixture was assayed in triplicate for cortisol and aldosterone on a cobas e602 (Roche Diagnostics) and LIAISON XL (DiaSorin) immunoanalyzer, respectively. The total allowable error (TEa) was ±0.4 μg/dL or ±20% for cortisol and ±2 ng/dL or ±20% for aldosterone. Results Flotation of the gel separator was observed at a dye concentration of 4.5% v/v and greater. For the cortisol interference study, the bias was <5% for the three pools at all contrast media concentrations. Aldosterone was also measured in these pools, as bias could affect ratios calculated for PA. Aldosterone interference occurred at contrast dye concentrations ranging from 12%-20% v/v. An average positive bias of 34% was observed in aldosterone samples spiked with contrast media relative to the saline control. Compared to sample pool controls without added saline or dye, measurements for cortisol and aldosterone were 19%-22% and 16-25% lower in media- and saline-spiked samples (20% v/v), respectively, indicating a logical dilution effect. Conclusions Contrast dye contamination of AVS specimens can cause gel flotation in lithium heparin PSTs, preventing their analysis. The presence of contrast media at certain concentrations interfered with the DiaSorin aldosterone assay, leading to falsely elevated results. No cortisol assay interference occurred in the presence of contrast media but results were falsely decreased due to sample dilution. Samples collected during AVS may be contaminated with contrast dye causing gel flotation to occur. This is indicative of a minimum contrast media concentration of 4.5% v/v. Aldosterone:cortisol ratios may be inaccurate due to the positive aldosterone immunoassay bias with contrast media contamination. Care should be taken when reporting and interpreting AVS results with suspected contamination.

Endocrine data provide further evidence of physiologic derangement in sea turtles affected by the Deepwater Horizon oil spill

This study was conducted to characterize the adrenocortical and thyroid status of Kemp’s ridley sea turtles Lepidochelys kempii that were affected by the Deepwater Horizon oil spill. A plasma aldosterone assay was validated for L. kempii, and it was used along with previously validated assays for corticosterone and free thyroxine to assess hormone concentrations of 30 L. kempii that were hospitalized due to oil exposure, representing 2 severities of oiling (lightly or heavily oiled). Hormone concentrations were also assessed in relation to 8 clinical biochemical analytes. Analysis of paired samples indicated that oiled turtles had significantly higher initial aldosterone and corticosterone concentrations, which declined during convalescence (average 96 and 90% decrease, respectively). Thyroxine concentrations significantly increased between admission and convalescence (average 65% increase). Initial biochemical data indicated significantly higher plasma potassium, ionized magnesium, and lactate concentrations compared to convalescent values. Aldosterone concentrations were positively correlated with corticosterone, negatively correlated with free thyroxine, and variably correlated with several clinical biochemical analytes. Results of this study indicate that L. kempii had robust adrenocortical activity after oiling, capture, and transport to the hospital, regardless of the degree of oiling, resulting in very high plasma concentrations of aldosterone and corticosterone. This study also confirms that aldosterone can be reliably measured in sea turtle plasma samples, providing another diagnostic tool for the physiologic assessment of this Critically Endangered species.

Recent progress in the diagnosis and treatment of primary aldosteronism.

Primary aldosteronism (PA) is caused by excessive secretion of aldosterone from the adrenal glands, with subsequent changes in the renin-angiotensin system. In Japan, chemiluminescent enzyme immunoassay is currently performed for aldosterone assay rather than the earlier method of radioimmunoassay. This change in aldosterone measurement methods has resulted in faster and more accurate measurement of blood aldosterone levels. Since 2019, esaxerenone, a mineralocorticoid receptor antagonist (MRA) with a non-steroidal skeleton, has been available in Japan for the treatment of hypertension. Esaxerenone has been reported to have various effects, such as strong antihypertensive and anti-albuminuric/proteinuric effects. Treatment of PA with MRAs has been reported to improve the patient's quality of life and to suppress the onset of cardiovascular events independent of their effects on blood pressure. Measuring renin levels is recommended for monitoring the extent of mineralocorticoid receptor blockade during MRA treatment. Patients receiving MRAs are prone to developing hyperkalemia, and combining MRAs with sodium/glucose cotransporter 2 inhibitors is expected to prevent severe hyperkalemia and provide additional cardiorenal protection. Mineralocorticoid receptor-associated hypertension is a broad concept of hypertension that includes not only PA, but also hypertension caused by borderline aldosteronism, obesity, diabetes, and sleep apnea syndrome. New findings on primary aldosteronism, which is part of MR-associated hypertension. Aldosterone measurements have been changed to the CLEIA method. Treatment of primary aldosteronism with MRAs has a variety of positive effects. CT-guided radiofrequency ablation and transarterial embolization are alternatives to surgery for aldosterone-producing adenomas. BP blood pressure, CLEIA chemiluminescent enzyme immunoassay, CT computed tomography, K serum potassium, MR mineralocorticoid receptor, MRA mineralocorticoid receptor antagonist, QOL quality of life, SGLT2i sodium/glucose cotransporter 2 inhibitor.

PS-C22-3: VALIDATION AND CLINICAL EVALUATION OF DIAGNOSTIC ABILITY OF NOVEL CHEMILUMINESCENT ENZYME IMMUNOASSAY OF PLASMA ALDOSTERONE CONCENTRATION.

Plasma aldosterone concentration has been usually measured by radioimmunoassay and chemiluminescent enzyme immunoassay which have demonstrated lack of high specificity and variability in assay performances. Liquid chromatography-tandem mass spectrometry is considered to be ideal measurement method of plasma aldosterone, however it takes relatively high cost and measurement time. We recently developed a novel non-competitive chemiluminescent enzyme immunoassay for plasma aldosterone concentrations by the fully automated assay system. We performed clinical validation of diagnostic ability of the new assay-based screening of 344 hypertensive patients including 133 patients with primary aldosterone producing adenoma, 100 patients with bilateral hyperaldosteronism, and 111 patients with essential hypertension. Passing-bablok analysis revealed that the new measurement of plasma aldosterone concentration was significantly correlated and almost equivalent to liquid chromatography-tandem mass spectrometry measurement of aldosterone; the regression slope and intercept were 0.962 and -0.043, and the correlation coefficient was 0.962, which is more similar than radioimmunoassay especially in lower range (< 10 ng/dL). Bland-Altman plot analysis with the mass-spectrometry measurement also demonstrated that both bias and limits of agreement with 95% confidence interval of the automated aldosterone assay were smaller than those of the radioimmunoassay, suggesting smaller systemic errors in the novel measurement. The lowest plasma aldosterone concentration and ratio of aldosterone-over-renin concentrations in aldosterone producing adenoma group were 6.0 ng/dL and 16.3 ng/dL per pg/mL/hr, respectively. We suggest if aldosterone-over-renin concentrations is over 15 ng/dL per pg/mL/hr, the patient should be performed confirmatory test for primary aldosteronism. The novel chemiluminescent enzyme immunoassay is clinically reliable alternative for conventional radioimmunoassay and liquid chromatography-tandem mass spectrometry to provide better throughput and cost-effectiveness in diagnosis of primary aldosteronism from larger number of hypertensive patients.

THE EXPLORATION OF THE RENINE ANGIOTENSIN SYSTEM IN NEPHROLOGY: EXPERIENCE OF THE NEPHROLOGY DEPARTMENT OF THE HEDI CHAKER UNIVERSITY HOSPITAL CENTER OF SFAX

Objective: Plasma renin and aldosterone assays are useful in clinical practice for the aetiological assessment of arterial hypertension (hypertension) and / or a disturbance of the electrolyte balance. The objective of our work is to describe the main indications exploration of the renin aldosterone system, its results, its diagnostic and etiological impact. Design and method: We conducted a retrospective study of 40 patients who received a renin / aldosterone dosage, collected in the Nephrology department at the Hédi Chaker CHU in Sfax for a period of 6 years from January 2014 until December 2020. Results: These are 21 women and 19 men with a sex ratio of 1.1. Hypertension was present in 82.5% of cases. The dosage indication was: hypertension with hypokalaemia in 52.5%, hypertension in young subjects in 20%, resistant hypertension and hypertension with incidentaloma in each 7, 5% of cases, and incidentaloma without HTA in each 5% of cases and in one case hypokalaemia without HTA. Aldosterone was elevated in 52.5% of cases. Renin was normal in 67.5% of cases, low in 25% and high in 7.5% of cases. The aldosterone / renin ratio was normal in 60% of cases, elevated, decreased and invalid in respectively 27.5%, 2.5% and 10%. The etiological investigation revealed: primary hyperaldosteronism in 42.5% of cases secondary to a Conn adenoma in 20% of cases, to adrenal hyperplasia in 17.5% of cases and with normal imaging in 5% of cases. Secondary hyperaldosteronism was confirmed in association with Liddle syndrome and renal artery stenosis in 2.5% of cases each. The other etiologies were pheochromocytoma in 12.5% of cases, Takayusu’s disease, tubulopathy in 2.5% of cases each. The dosage was non-contributory in 7.5% of cases and normal in 25% of cases. Conclusions: The exploration of the renin angiotensin aldosterone system has several indications, mainly in hypertension with hypokalaemia. It can help make the etiological diagnosis and guide therapeutic management.

Interference in aldosterone assay revealed by hemolysis.

Interference in aldosterone assay revealed by hemolysis.

Recalibrating Interpretations of Aldosterone Assays Across the Physiologic Range: Immunoassay and Liquid Chromatography-Tandem Mass Spectrometry Measurements Under Multiple Controlled Conditions.

ContextClinicians frequently rely on aldosterone thresholds derived from older immunoassays to diagnose primary aldosteronism. Liquid chromatography–tandem mass spectrometry (LC-MS/MS) is increasingly widespread and reported to yield lower aldosterone concentrations.ObjectiveGiven the health impact of incorrect interpretations of aldosterone levels, we compared measurements using LC-MS/MS and immunoassay across the full range of aldosterone physiology by evaluating distinct regulation by angiotensin II and adrenocorticotropin (ACTH).MethodsNormotensive volunteers underwent prospective characterization of aldosterone production by immunoassay and LC-MS/MS during 4 conditions (n = 188): oral sodium suppression and restriction (to assess angiotensin II–mediated aldosterone production) and dexamethasone suppression and cosyntropin stimulation (to assess ACTH-mediated aldosterone production).ResultsSerum aldosterone concentrations by LC-MS/MS and immunoassay had a correlation of 0.69 (P < .001), with good agreement (intraclass correlation 0.76; 95% CI 0.52-0.87). Aldosterone was lower by LC-MS/MS than immunoassay (median 10.5 [3.8, 21.9] vs 19.6 [9.5, 28.0] ng/dL; P < .001), with an average difference of 37.2%. The most notable discrepancy was in the clinically discriminatory range <20 ng/dL: 9.9 (7.1, 13.8) ng/dL using immunoassay corresponded to 5.5 (1.4, 8.9) ng/dL by LC-MS/MS (P < .001). Following oral sodium suppression, the aldosterone-to-renin ratio was 4-fold higher using immunoassay (27.2 [19.7, 62.4] vs 6.4 [3.5, 19.1] ng/dL per ng/mL/hour; P < .001).ConclusionAldosterone measurements are substantially lower by LC-MS/MS than immunoassay across the full physiologic range, especially when aldosterone levels were less than 20 ng/dL. These findings highlight the need to recalibrate diagnostic interpretations when measuring aldosterone via LC-MS/MS and provide insights into potential biologic causes of assay differences.

Validation of the Fujirebio Lumipulse G1200 aldosterone assay for measurements during adrenal venous sampling for primary hyperaldosteronism

Article Validation of the Fujirebio Lumipulse G1200 aldosterone assay for measurements during adrenal venous sampling for primary hyperaldosteronism was published on November 1, 2021 in the journal Clinical Chemistry and Laboratory Medicine (CCLM) (volume 59, issue 12).

DEVELOPING A MOST EQUIVALENT ALDOSTERONE MEASUREMENT TO LC-MS/MS BY A NOVEL HIGH-QUANTITATIVE NONCOMPETITIVE CHEMILUMINESCENCE IMMUNOASSAY

Objective: Measurement of plasma aldosterone and renin concentration, or activity, is useful for selecting antihypertensive agents and detecting hyperaldosteronism in hypertensive patients. However, it takes several days to get results even if measured by inaccurate radioimmunoassay, or we must accept high-cost LC/MS, and development of a more rapid and accurate substitute has been long hoped. We have developed a novel, fully-automated, high-quantitative noncompetitive chemiluminescence immunoassay (NC-CLEIA) for detecting aldosterone in serum and plasma, and its performance is evaluated as compared to LC/MS measurement. Design and method: Recently a unique anti-metatype antibody, which recognizes the immunocomplex of aldosterone and its monoclonal antibody, was established. Using this antibody for sensing permitted the construction of non-competitive assay for the detection of aldosterone. The reaction protocol of novel aldosterone assay is the following. In the 1st reaction, aldosterone in patient's sample is captured on anti-body coated magnetic particles. Alkaline phosphatase-conjugated anti-metatype antibody is added and incubated as 2nd reaction following a wash. Then substrate solution is added after washing immunocomplex. The resulting reaction signals are proportional to the amount of aldosterone in the sample allowing quantitative determination of in serum or plasma sample. The overall reaction is completed within 30 min. Results: Limit of blank (LoB), limit of detection (LoD) and limit of quantitation (LoQ) of our NC-CLEIA aldosterone assay were 0.09 ng/dL, 0.21 ng/dL and 0.57 ng/dL, respectively. NC-CLEIA aldosterone measurements were linearly well correlated with LC/MS aldosterone measurements (N = 130, y = 1.027x - 0.23 ng/dL, Spearman's p = 0.996, p &lt; 0.0001). Bland-Altman plot analysis between NC-CLEIA and LC-MS/MS of aldosterone revealed a bias of 0.40 ng/dL with the limits of agreement of -4.60 and 5.41 ng/dL with 95% confidence interval. Conclusions: Our novel NC-CLEIA aldosterone assay was well-correlated and had only a very low bias with LC-MS/MS method and also was able to accurately quantify low level samples even in essential hypertension patients. This assay may be useful for the routine analysis of aldosterone and for the screening and diagnosis of PA from large number of hypertensive patients.

Canine isolated hypoaldosteronism

AbstractA 2‐year‐old female neutered English bull terrier presented with a history of behavioural change (depression, lethargy, avoidance of light), a mild increase in thirst and urination and two episodes of collapse. General physical and neurological examinations were unremarkable. Initial investigations documented hyponatremia and hyperkalaemia. An adrenocorticotropic hormone (ACTH) stimulation test excluded hypocortisolism. Aldosterone concentrations obtained pre‐ and post‐ACTH stimulation were both undetectably low. Paired renin and aldosterone assays confirmed hyperreninemic hypoaldosteronism.The patient was treated with oral mineralocorticoid supplementation which resulted in a rapid improvement in both clinical signs and electrolyte concentrations; she remained well on treatment during a 5‐year follow‐up period.Isolated hypoaldosteronism is infrequently reported in the dog but should be considered in cases where hypoadrenocorticism is suspected based on electrolyte abnormalities, but hypocortisolism has been excluded.

Subclinical hypernatraemia in a population of endurance racing sled dogs

Electrolyte disturbances occur in both human and veterinary endurance athletes; however, hypernatraemia is poorly documented in dogs. To further explore electrolyte changes in canine endurance athletes, we collected blood from two teams of dogs (n=16) participating in the mid-distance (336 km) CanAm race. Serum samples were collected 36 hours before the start and within 20 minutes of race completion. Serum was similarly collected from 18 dogs withdrawn after completing 264 km. Biochemical profiles and aldosterone assays were performed. Mean serum sodium (&gt;155 mEq/l) and corrected chloride concentrations were significantly increased (P&lt;0.01) from baseline in finishing and withdrawn dogs; however, unlike sodium, corrected chloride concentrations remained within the reference interval. Serum phosphorous, hepatic enzymes, cholesterol, creatinine kinase, blood urea nitrogen, globulin, glucose, and iron concentrations were also significantly increased (P&lt;0.01) compared to baseline in both finishing and withdrawn dogs. Both mean serum aldosterone and urea nitrogen concentrations were significantly increased (P&lt;0.01) from baseline in finishing and withdrawn dogs, with finishers having greater concentrations than withdrawn dogs (P&lt;0.01). Pre-race and matched finishing dog populations were then used for correlation analysis. Serum sodium concentrations were significantly (P&lt;0.01) and strongly correlated with chloride (r=0.92), albumin (r=0.88), total protein (r=0.87), globulin (r=0.81), and potassium (r=0.86). Serum sodium concentrations were not significantly correlated with serum aldosterone concentrations (r=0.04, P=0.87). This study uniquely described subclinical hypernatraemia in the canine endurance athlete. The data lend support of dehydration through free water loss as a cause of hypernatraemia likely compounded by insufficient replenishment by drinking. Elevations in aldosterone concentrations in the face of hypernatraemia may be attributed to concurrent extra-renal hypotonic water losses, counter regulatory hormone influences, or physiological hyperthermia. Such findings demonstrate a degree of clinical tolerance for euvolemic driven hypernatraemia in endurance sled dogs, while highlighting the need for appropriate water supplementation.

SUN-LB95 Developing a Highly Equivalent Non-Competitive Chemiluminescence Immunoassay Aldosterone Measurement to LC/MS

Background Measurement of plasma aldosterone and renin concentration, or activity, is useful for selecting antihypertensive agents anddetecting hyperaldosteronism in hypertensive patients. However, it takes several days to get results even if measured by inaccurateradioimmunoassay, or we must accept high-cost LC/MS, and development of a more rapid and accurate substitute has been long hoped. We havedeveloped a novel, fully-automated, high-quantitative noncompetitive chemiluminescence immunoassay (NC-CLEIA) for detecting aldosterone inserum and plasma, and its performance is evaluated as compared to LC/MS measurement. Methods Recently a unique anti-metatype antibody,which recognizes the immunocomplex of aldosterone and its monoclonal antibody, was established. Using this antibody for sensing permittedthe construction of non-competitive assay for the detection of aldosterone. The reaction protocol of novel aldosterone assay is the following. Inthe 1st reaction, aldosterone in patient’s sample is captured on anti-body coated magnetic particles. Alkaline phosphatase-conjugated antimetatypeantibody is added and incubated as 2nd reaction following a wash. Then substrate solution is added after washing immunocomplex.The resulting reaction signals are proportional to the amount of aldosterone in the sample allowing quantitative determination of in serum orplasma sample. The overall reaction is completed within 30 min. Results Limit of blank (LoB), limit of detection (LoD) and limit of quantitation(LoQ) of our NC-CLEIA aldosterone assay were 0.09 ng/dL, 0.21 ng/dL and 0.57 ng/dL, respectively. NC-CLEIA aldosterone measurements werelinearly well correlated with LC/MS aldosterone measurements (N = 130, y = 1.027x - 0.23 ng/dL, Spearman’s ρ = 0.996, P< 0.0001). Bland-Altmanplot analysis between NC-CLEIA and LC-MS/MS of aldosterone revealed a bias of 0.40 ng/dL with the limits of agreement of -4.60 and 5.41 ng/dLwith 95% confidence interval. Conclusion Our novel NC-CLEIA aldosterone assay was well-correlated and had only a very low bias with LC-MS/MSmethod and also was able to accurately quantify low level samples even in essential hypertension patients. This aldosterone assay can be a most equivalent to LC-MS/MS measurement with a low cost of 12 $ and a short measuring time of 30 minutes.

A comprehensive quality control system suitable for academic research: application in a pediatric study.

Aim: Clinical research in pediatrics is progressively initiated by academia. As the reliability of pharmacodynamic measures is closely linked to the quality of bioanalytical data, bioanalytical quality assurance is crucial. However, clear guidance on comprehensive bioanalytical quality monitoring in the academic environment is lacking. Methods & results: By applying regulatory guidelines, international recommendations and scientific discussions, a five-step quality control system for monitoring the bioanalysis of aldosterone by immunoassay was developed. It comprised performance qualification, calibration curve evaluation, analysis of the intra- and inter-run performance via quality control samples, incurred sample reanalysis and external quality assessment by interlaboratory testing. A total of 55 out of 70 runs were qualified for the quantification of aldosterone in the study sample enabling the evaluation of 954 pediatric samples and demonstrating reliability over the 29-month bioanalysis period. Conclusion: The bioanalytical quality control system successfully monitored the aldosterone assay performance and proved its applicability in the academic environment.

Atypical hypoadrenocorticism in a dog with chronically elevated serum alanine aminotransferase (ALT) activity

A 10-year-old male, castrated, Beagle dog was presented for subclinical, chronic elevated serum alanine aminotransferase activity on serial serum biochemistry profiles. Additionally, mild hypocholesterolaemia, hypoalbuminaemia and hyperammonaemia were identified. Microhepatica...

SAT-012 Urinary Aldosterone Assay Using LC-MS/MS Could Improve Primary Aldosteronism Screening

Primary aldosteronism (PA) is the first cause of endocrine hypertension accounting for about 6% of all cases of hypertension. According to international guidelines, PA screening is based on plasma aldosterone-to-renin concentration ratio (ARR) computation. Nevertheless, measurement of urine aldosterone excretion may be of interest since it integrates aldosterone secretion over 24 hours. However, available urine aldosterone immuno-assays have poor specificity. In this context, we developed a new aldosterone assay using liquid chromatography and tandem mass spectrometry detection (LC-MS/MS) to recover specifically urine free aldosterone and glucuronide metabolites after 18-hour acid hydrolysis. Our method was validated according to FDA recommendations, and covers the expected range of aldosterone concentrations found in 24-hour urine collection (from 1.10 to 75 nM) with improved specificity. It has a within-run precision below 2% and a maximum between-run precision of 5.6%. The diagnostic performance of the assay was assessed in a cross-sectional retrospective study that included 234 subjects: 63 healthy volunteers (HV), 107 patients with essential hypertension (EH) and 64 PA patients. Final diagnosis was based on routine hormone measurements in accordance with international guidelines. Median (5th to 95th percentile) of 24-hour urine aldosterone excretion was 19.5 (5.2-53.4) nmol/24h in HV, 39.1 (13.3-97.4) nmol/24h in EH and 91.4 (40.6-225.3) nmol/24h in PA subjects. By ROC curve analysis (area 0.864), a cutoff value of aldosterone excretion of 65 nmol/24h yielded a 76.6% sensitivity and 78.5% specificity to discriminate PA from EH patients. 24-hour urinary aldosterone:creatinine ratio was more discriminant than 24-hour aldosterone excretion, with ratios (nmol/mmol) of 1.42 (0.5-3.9) for HV, 3.4 (1.3-7.9) for EH and 6.9 (2.5-30.0) for PA. By ROC curve analysis (area 0.867) a cutoff value of 24-hour urinary aldosterone:creatinine ratio of 5.0 nmol/mmol had 81.3% sensitivity and 81.3% specificity to discriminate PA from EH patients. Finally, 11% of our 64 PA patients showed a urinary aldosterone:creatinine ratio above this suggested cutoff value while ARR was below cut-off value. In conclusion, LC-MS/MS measurement of urinary aldosterone is a specific, sensitive and effective method for the diagnosis of PA.

Sex‐Differences in Renal Na+ Regulatory Mechanisms During Acclimation to a High Salt Diet

Hypertension is more prevalent in men compared to premenopausal women. Maintenance of Na+ homeostasis is an essential component of blood pressure regulation, and defects in the renal capacity to appropriately excrete Na+ are fundamental mechanisms involved in the initiation of salt‐sensitive hypertension. We recently reported that female rats elicit a more rapid natriuretic response to a high salt (HS) diet compared to males. The overall goal of the current study was to determine the natriuretic signaling pathway(s) involved in the enhanced ability of females to handle HS challenges. Male and female Sprague Dawley rats (16–18 weeks old) were placed into metabolic cages on normal salt (NS, 0.49% NaCl) followed by HS (4% NaCl) diet for 5 days. 24‐hour urine samples were assessed for endothelin‐1 (ET‐1), aldosterone (ALD) and norepinephrine (NE). On NS, urinary ET‐1 was significantly higher in females, compared to males; no sex‐differences were detected in urinary ALD or NE. In males, urinary ET‐1 was increased (10.2±0.8 vs. 5.6±1.0 pg/kg/day, n=8 each, p=0.002) and urinary ALD was decreased on day 1 HS relative to NS (6.1±0.7 vs. 15.2±2.6 μg/kg/day, n=5 each, p=0.02); no significant changes were observed in ET‐1 or ALD in females on day 1 HS. Urinary NE remained unchanged during the HS challenge in both sexes. Ingenuity Pathway Analysis (IPA) of RNA sequencing data from inner medullae from males and females on NS identified an enrichment (p=3.11E‐04) of transcripts in the ET‐1 signaling pathway in females, with the abundance of 35/190 (18.4%) of pathway transcripts being at least 1.5‐fold different in abundance between sexes. Further, IPA predicted that ET‐1 signaling is activated in female inner medulla, relative to males. Previous studies showed that interleukin‐1β (IL‐1β) stimulates renal ET‐1 production. Thus we tested whether renal IL‐1β is upregulated in response to HS in a sex‐dependent manner. Renal IL‐1β was assessed by ELISA and IHC. Renal cortical IL‐1β was significantly increased on day 1 HS, relative to NS, only in males (8.1±0.3 vs. 6.4±0.3 pg/mg protein, n=9 each, p=0.03). Our data suggest that activation of IL‐1β/ET‐1 and inhibition of ALD signaling pathways contribute to acclimation to HS challenges in males. We further suggest that the already activated renal ET‐1 signaling in females under NS may contribute to the enhanced ability to acclimate to HS challenges observed in females.Support or Funding InformationFunded by AHA 18CDA34110010 and 15POST25090329 to EYG, and P01 HL136267 to JSP and DMP. We appreciate Drs. Celso and Elise Gomez‐Sanchez's help with ALD assay.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

A1728 Measurement of aldosterone

Objectives: To compare aldosterone assay by RIA with LC-MS/MS and to evaluate the performance of proposed LC-MS/MS-specific cut-offs for primary aldosteronism (PA) screening and confirmatory testing. Methods: Peripheral aldosterone concentration (PAC) was tested by both methods among 52 patients during fludrocortisone suppression testing (FST). Direct renin concentration (DRC) was measured by CLIA. The proposed PACLC-MS/MS cut-offs for the aldosterone/renin ratio (ARR) and FST were derived from the regression equation obtained from our previous in-house comparison between two assays. Results: The obtained equation was PACLC-MS/MS = 0.79 × PACRIA-28.1 (R2 = 0.87, n = 200). In this study, median PACLC-MS/MS was 29.3% lower (p < 0.05) than PACRIA. A positive correlation (Spearman coefficient 0.92, p < 0.01) and linear relationship (p < 0.01, R2 = 0.81, n = 208) were observed between the two assays, with a positive bias of 34.5% (95% limits of agreement: −34.2% to 103.3%) for RIA. Forty-one patients showed conclusive FSTs (37 consistent and 4 inconsistent by two assays) A good agreement (Kappa coefficient 0.74, p < 0.01) and no differences were observed between the current FST day 4 upright PACRIA cut-off of 165 pmol/L and the proposed PACLC-MS/MS cut-off of 130 pmol/L. Among the 37 patients with consistent FSTs, no differences were observed in sensitivity (89.7% vs 93.1%) and specificity (87.5% for both) between the current ARRRIA cut-off of 70 and the proposed ARRLC-MS/MS cut-off of 55. Conclusion: Adjustment of the current cut-off for PA diagnostic testing is necessary if PACLC-MS/MS is measured. Our preliminary results revealed that the proposed cut-offs of 55 for the ARR (PACLC-MS/MS/DRC) and 130 pmol/L for FST day 4 upright PACLC-MS/MS perform as well as the current RIA threshold values.

Renin Activity and Aldosterone Assay Among Nigerians with Hypertension and Normotension: An Insight into Normative Values and Clinical Correlates.

Plasma renin activity (PRA) and aldosterone tend to differ between Blacks and Caucasians and studies are very scarce among Africans. We therefore aimed to determine the normative value of plasma renin activity and serum aldosterone among school teachers in Nigeria with normal blood pressure compared with their hypertensive counterparts and relevant clinical/ demographic associations. Plasma renin activity and serum aldosterone were measured using the kits provided by Diagnostic Biochem, Canada among randomly selected school teachers recruited as part of a study to assess their total cardiovascular risks. Mean serum values were compared between normotensive and hypertensive participants and were correlated with clinical and demographic parameters. Statistical analysis was done using SPSS 17.0, Chicago, Ill, USA. P <0.05 was taken as statistically significant. The mean PRA level of all study participants was 0.80 ± 0.85 ng/mL.h (mean ± SD) while the mean serum level of aldosterone was 93.9 ± 60.9 pg/ml. The mean aldosterone: renin ratio was 446.5 ± 958.2. The frequency of occurrence of hypertension was 29%. Only plasma renin activity was significantly correlated with systolic and diastolic blood pressure, age and the rate pressure product (a measure of cardiovascular risk). The finding of a higher mean PRA among hypertensive subjects is definitely related to the antihypertensive medications being taken including beta blockers and angiotensin converting enzyme inhibitors among others. The prevalence of high aldosterone/ renin ratio which could reflect the proportion of primary aldosteronism was 10.8%. Nigerians have a low renin activity compared to their Caucasian counterpart. PRA may be an important determinant of blood pressure among Nigerians. Appropriate drugs that target phenotypic status of PRA and aldosterone may be useful in the management of hypertension and the choice of pharmacotherapy among Nigerians.

PP.27.21] HYPERTENSION AND PRIMARY ALDOSTERONISM

Objective: At the age of 45 years, more than 50% of the population suffers from hypertension. It is in most cases essential. However, in some situations, a secondary origin must be sought. Primary hyperaldosteronism is the most frequent cause after nephropathy. Design and method: Our study is retrospective on a year (March 2015-March 2016), including hypertensive patients who received a renal aldosterone (R/A) assay in the presence of secondary hypertension after eliminating unilateral or bilateral parenchymal nephropathy. Results: We collected sixteen patients with an average age 46 years. The average seniority of the high blood pressure was 3 years. primary hyper aldosternism was suspected face to a hypertension associated wih hypokalaemia in 10 cases, in front of a resistant hypertension in 4 cases and before the fortuitous discovery of an adrenal nodule in 2 patients. The results of the assays were in favor of a primary hyper aldosternism on average in 8 patients A/R ratio up to 28 according to the usual values of the laboratory). An adrenal nodule was found in 6 of these patients. Therapeutic management was adrenalectomy in 2 of these patients, and spironolacton treatment for the others. Conclusions: Primary hyperaldosteronism is probably under-diagnosed and affects about 10% of hypertensive patients. The earlier diagnosis, the more likely avoiding cardiovascular and renal complications.

PP.27.02] PERFORMANCE OF FULLY AUTOMATED CHEMILUMINESCENCE ALDOSTERONE IMMUNOASSAY IN A POPULATION OF HYPERTENSIVE PATIENTS

Objective: Verify, retrospectively the ARR threshold in a population of hypertensive patients investigated for PA, and to attest the precision of the new method in intra venous salt loading (ivSLT) as confirmatory test. Design and method: We compared aldosterone results obtained with the CL method and RIA in stored blood samples from hypertensive patients investigated for PA (102 baseline and 85 after ivSLT). Results: A very good correlation between RIA and CL aldosterone assays was found in the all population for both aldosterone (r 0.922) and ARR (r 0.977). For the ARR, Deming regression demonstrated a good accordance between methods, and according to the fit model, considering our institutional cut-off of 32 pg/ml/pg/ml, the corresponding ARR cut off with CL aldosterone assay is 20 pg/ml/mUL. However, the correlation was was lower in the low end of aldosterone concentrations (r 0.676 for aldosterone <100 pg/ml by RIA). Accordingly, results of ivSLT with both assays were concordant in only 66% of patients. Conclusions: CL assay displays an accuracy similar to RIA for ARR screening, but its diagnostic accuracy remains suboptimal in the low end of aldosterone concentrations, which characterizes the setting of confirmatory tests such as ivSLT.