State of the art of aldosterone immunoassays. A multicenter collaborative study on the behalf of the Cardiovascular Biomarkers Study Group of the Italian Section of European Society of Ligand Assay (ELAS) and Società Italiana di Biochimica Clinica (SIBIOC)

Intact fibroblast growth factor 23 in heart failure with reduced and mildly reduced ejection fraction

BACKGROUND

Fibroblast growth factor-23 (FGF23) has been associated to left ventricular (LV) hypertrophy and heart failure (HF) severity. We aimed to investigate the clinical correlates and prognostic value of intact FGF23 (iFGF23) in HF patients.

METHODS

Patients with stable HF and left ventricular ejection fraction (LVEF) < 50% were prospectively enrolled, managed according to current recommendations and followed over time. iFGF23 was measured at baseline with a fully automated immuno-chemiluminescent assay.

RESULTS

We enrolled 150 patients (82% males; median age 65 years). First, second, and third iFGF23 tertiles were < 35.2 pg/mL, 35.2-50.9 pg/mL, and > 50.9 pg/mL. LVEF decreased from the first iFGF23 tertile to the third tertile (p = 0.014). N-terminal pro-B-type natriuretic peptide (NT-proBNP) increased from the first to the third tertile (p = 0.001), while peak oxygen consumption decreased (p < 0.001). Thirty-five patients (23%) experienced the primary endpoint (all-cause death or HF hospitalization at 5 years), and 26 (17%) the secondary endpoint (all-cause death at 5 years). On multivariable analysis, iFGF23 independently predicted the primary endpoint on top of age, gender and LVEF (HR 4.6 [95% CI 2.1-10.3], p < 0.001), age, gender and eGFR (HR 4.1 [95% CI 1.6-10.3], p = 0.003), as well as age, gender and NT-proBNP (HR 3.6 [95% CI 1.6-8.2], p = 0.002). iFGF23 even reclassified patient risk on top of all the 3 models, with NRI values of 0.65 (95% CI 0.30-1.01), 0.55 (95% CI 0.25-0.88), and 0.60 (95% CI 0.24-0.96), respectively (both p < 0.001).

CONCLUSIONS

Circulating iFGF23 is associated with disease severity and outcome in HF patients with reduced and mildly reduced ejection fraction.

Renin, aldosterone, the aldosterone-to-renin ratio, and incident hypertension among normotensive subjects from the general population

AIMS

To investigate the predictive ability of direct plasma renin and aldosterone concentrations as well as their ratio [aldosterone-to-renin (ARR)] for incident hypertension in the general population.

METHODS AND RESULTS

Concentration of renin and aldosterone were measured by a chemiluminescence immunoassay using the fully automated LIAISON® platform (DiaSorin) among 5362 participants of the population-based Gutenberg Health Study, who were normotensive and had no clinically overt cardiovascular disease at baseline. During a follow-up period of 5 years, 18.6% (n = 996) developed a new-onset hypertension. Comparing extreme quartiles of biomarker distribution, the relative risk (RR) for incident arterial hypertension was found to be 1.58 [95% confidence interval (CI) 1.25-2.00; P = 0.00015; Q1 vs. Q4ref] for renin; 1.29 (95% CI 1.05-1.59, P = 0.018; Q4 vs. Q1ref) for aldosterone and 1.70 (95% CI 1.33-2.12; P < 0.0001; Q4 vs. Q1ref) for ARR after multivariable adjustment in men. In females, only high ARR was independently predictive for incident hypertension over 5 years [RR 1.29 (95% CI 1.04-1.62); P = 0.024]. Even in the subgroup of individuals having biomarker concentrations within the reference range, high ARR was predictive for new-onset hypertension in men [RR 1.44 (95% CI 1.13-1.83); P = 0.003]. Finally, synergistic effects of co-prevalent obesity and ARR on incident hypertension were also demonstrated, resulting in markedly higher risk estimates as seen for biomarker alone [RR of 2.70 (95% CI 2.05-3.6) for Q4 of ARR and having body mass index ≥ 30 kg/m2 vs. low ARR (Q1ref) and normal weight; P < 0.0001].

CONCLUSION

Among normotensives from the general population ARR possesses a stronger predictive value for incident hypertension than renin or aldosterone alone. The prediction of arterial hypertension by ARR was even stronger in obese subjects.

Performance of the aldosterone-to-renin ratio as a screening test for primary aldosteronism in primary care

Primary aldosteronism (PA) is the most common and potentially curable form of secondary hypertension, affecting 5-10% of primary care patients with hypertension. Primary care physicians have an important role in initiating the screening for PA in patients with hypertension and referring to a specialist service depending on the screening test results. The currently recommended screening test for PA is the plasma aldosterone-to-renin ratio (ARR). Test results are influenced by medications so careful patient preparation is required including adjusting existing antihypertensive medications to avoid diagnostic errors. A range of laboratory method-dependent ARR thresholds are used for the screening of PA around the world. Periodic clinical audits and case reviews by clinicians and the laboratory may help refine the local thresholds. Patients with an abnormally elevated ARR should be referred to a specialist for confirmatory testing while patients with a high pre-test probability but a normal ARR could have a repeat test in view of the within-individual variability. Despite the heterogenous ARR thresholds, measuring the ARR is still more likely to detect PA than not screening at all.

Early Renin Recovery After Adrenalectomy in Aldosterone-Producing Adenomas: A Prospective Study

The aim of the study was to clarify the relationship and the time of aldosterone and renin recoveries at immediate and long-term follow-up in aldosterone-producing adenoma (APA) patients who underwent adrenalectomy. Prospective and longitudinal protocol in a cohort of APA patients was followed in a single center. Among 43 patients with primary aldosteronism (PA), thirteen APA patients were enrolled in this study. Blood was collected for aldosterone, renin, potassium, creatinine, cortisol, and ACTH before and 1, 3, 5, 7, 15, 30, 60, 90, 120, 180, 270, 360 days after adrenalectomy. At diagnosis, most patients (84%) had hypokalemia and high median aldosterone levels (54.8; 24.0-103 ng/dl) that decreased to undetectable (<2.2) or very low (<3.0) levels between fifth to seventh days after surgery; then, between 3-12 months, its levels gradually increased to the lower normal range. The suppressed renin (2.3; 2.3-2.3 mU/l) became detectable between the fifteen and thirty days after surgery, remaining normal throughout the study. The aldosterone took longer than renin to recover (60 vs.15 days; p<0.002) and patients with higher aldosterone had later recovery (p=0.03). The cortisol/ACTH levels remained normal despite the presence of a post-operative hypoaldosteronism. Blood pressure and antihypertensive requirement decreased after adrenalectomy. In conclusion, our prospective study shows the borderline persistent post-operative hypoaldosteronism in the presence of early renin recovery indicating incapability of the zona glomerulosa of the remaining adrenal gland to produce aldosterone. These findings contribute to the comprehension of differences in renin and aldosterone regulation in APA patients, although both are part of the same interconnected system.

The simultaneous quantitative detection of multiple hormones based on PS-MS: affinity capture by a single antibody

Here, we utilized single antibody to capture and separate multiple hormones from samples to avoid LC procedures and MS/MS detection to realize simultaneously qualitative and quantitative analysis of multiple molecules in a single run.

Patients with cardiac amyloidosis have a greater neurohormonal activation than those with non-amyloidotic heart failure

BACKGROUND

Neurohormonal activation has never been investigated in patients with cardiac amyloidosis (CA).

METHODS

Forty-seven patients with amyloid light-chain (AL)-CA and 61 with transthyretin (ATTR)-CA were matched to non-amyloidotic heart failure (HF) patients based on age, sex, left ventricular ejection fraction ranges, renal function and HF therapies. N-terminal pro-B-type natriuretic peptide (NT-proBNP), norepinephrine and renin were dosed. The primary and secondary endpoints were 1-year cardiovascular death or HF hospitalisation, and 5-year cardiovascular death, respectively.

RESULTS

Patients with AL-CA had a 10-fold higher NT-proBNP than HF patients (6548 ng/L [2059-15,097] vs. 692 [243-2241], p < 0.001), and slightly higher norepinephrine (595 ng/L [383-869] vs. 416 [250-693], p = 0.047). Patients with ATTR-CA had higher NT-proBNP (3984 ng/L [2275-9505] vs. 1751 [470-4768], p = 0.006), norepinephrine (552 ng/L [344-855] vs. 441 [323-601], p = 0.020), and renin (14 mU/L [8-80] vs. 10 [4-34], p = 0.017). Patients with AL- or ATTR-CA had more often 2 or 3 neurohormones above the corresponding upper reference limits than matched HF patients. NT-proBNP and aldosterone were univariate predictors of the primary endpoint in patients with ATTR-CA, but not in matched controls. NT-proBNP and renin predicted the secondary endpoint in patients with AL-CA, but not in matched controls.

CONCLUSIONS

Patients with CA display a neurohormonal activation, with some prognostic significance.

Norepinephrine, plasma renin activity and cardiovascular mortality in systolic heart failure

OBJECTIVE

We analysed the circulating levels and prognostic value of N-terminal pro-B-type natriuretic peptide (NT-proBNP), norepinephrine (NE), epinephrine (E), plasma renin activity (PRA) and aldosterone in patients with systolic heart failure (HF) receiving therapies that target the sympathetic system and the renin-angiotensin-aldosterone axis.

METHODS

We retrieved data from consecutive HF outpatients with left ventricular ejection fraction (LVEF) <50% and available neurohormones, evaluated at a tertiary referral centre for HF from 1999 to 2016.

RESULTS

Patients (n=1477) were aged 66±13 years, 75% were men, median LVEF was 32% (IQR 25-38), 77% had LVEF <40% and 44% ischaemic HF. At the time of sampling, 69% were on beta-blockers, 75% on ACE inhibitors/angiotensin receptor blockers and 48% on mineralocorticoid receptor antagonists vs 88%, 87% and 66%, respectively, after therapy optimisation. Median NT-proBNP, NE, E, PRA and aldosterone were 1441 ng/L, 494 ng/L, 30 ng/L, 1.2 ng/mL/hour and 130 ng/dL, respectively. Over a 4.8-year follow-up (2.4-8.2), 376 patients died from cardiovascular causes (26%). NT-proBNP and PRA predicted cardiovascular mortality after adjusting for all other univariable predictors. The risk of cardiovascular death increased by 8% or 7% per each doubling of PRA in 2 models considering therapies at the time of sampling or after therapy optimisation. PRA improved metrics of reclassification and discrimination, and independently predicted outcome even in the LVEF <40% subgroup.

CONCLUSIONS

In patients with HF with LVEF <50% or <40%, PRA shows independent prognostic significance from a model that includes NT-proBNP, and might represent an additive tool for risk stratification.

Renin profiling predicts neurohormonal response to sacubitril/valsartan

AIMS

Clinical trials and observational cohorts show that beneficial effects of sacubitril/valsartan are less strong in an appreciable proportion of patients with heart failure with reduced ejection fraction (HFrEF). Lower blood pressure and impaired renal function predict suboptimal sacubitril/valsartan titration and a less favourable response. Circulating renin encompasses neurohormonal activation, intravascular volume, and renal function. We hypothesized that renin may predict response to sacubitril/valsartan, assessed by changes in N-terminal fraction of pro-brain natriuretic peptide (NT-proBNP).

METHODS AND RESULTS

We performed a prospective, open-label, real-life cohort study. The study population consisted of 80 consecutive HFrEF patients (age 66 ± 10 years, 83% men) planned to initiate sacubitril/valsartan. Clinical and biohumoral assessment, including a full neurohormonal panel, was performed at baseline and at 1, 3, and 6 month follow-up. Response to sacubitril/valsartan was defined as ≥30% reduction in NT-proBNP levels from baseline to 6 months. Patients in the lower renin tertile had higher blood pressure and plasma sodium concentration (all P < 0.05). At follow-up, 38 patients (48%) were classified as responders. Circulating renin was lower in the responder group compared with non-responders (19.8 mU/L, IQR 3.7-78.0 mU/L vs. 55.0 mU/L, IQR 16.4-483.1 mU/L; P = 0.004). After adjustment for age, renal function, and blood pressure, renin was independently associated to response to sacubitril/valsartan (P = 0.018).

CONCLUSIONS

In our preliminary study, we show that circulating renin predicts reduction in NT-proBNP levels after sacubitril/valsartan initiation in HFrEF patients. Renin assessment might be useful to discriminate potential responders from the subgroup with a weaker expected benefit, thus needing a closer, tailored management strategy.

Noncardiac Versus Cardiac Mortality in Heart Failure With Preserved, Midrange, and Reduced Ejection Fraction

Background

A thorough analysis of noncardiac determinants of mortality in heart failure (HF) is missing. Furthermore, evidence conflicts on the outcome of patients with HF and no or mild systolic dysfunction. We aimed to investigate the prevalence of noncardiac and cardiac causes of death in a cohort of chronic HF patients, covering the whole spectrum of systolic function.

Methods and Results

We enrolled 2791 stable HF patients, classified into HF with reduced ejection fraction (HFrEF; left ventricular ejection fraction [EF] <40%), HR with midrange EF (HFmrEF; left ventricular EF 41–49%), or HF with preserved EF (HFpEF; left ventricular EF ≥50%), and followed up for all‐cause, cardiac, and noncardiac mortality (adjudicated as due to cancer, sepsis, respiratory disease, renal disease, or other causes). Over follow‐up of 39 months, adjusted mortality was lower in HFpEF and HFmrEF versus HFrEF (hazard ratio: 0.75 [95% CI, 0.67–0.84], P<0.001 for HFpEF; hazard ratio: 0.78 [95% CI, 0.63–0.96], P=0.017 for HFmrEF). HFrEF had the highest rates of cardiac death, whereas noncardiac mortality was similar across left ventricular EF categories. Noncardiac causes accounted for 62% of deaths in HFpEF, 54% in HFmrEF and 35% in HFrEF; cancer was twice as frequent as a cause of death in HFpEF and HFmrEF versus HFrEF. Yearly rates of noncardiac death exceeded those of cardiac death since the beginning of follow‐up in HFpEF and HFmrEF.

Conclusions

Noncardiac death is a major determinant of outcome in stable HF, exceeding cardiac‐related mortality in HFpEF and HFmrHF. Comorbidities should be regarded as main therapeutic targets and objects of dedicated quality improvement initiatives, especially in patients with no or mild systolic dysfunction.

Sympathetic and renin-angiotensin-aldosterone system activation in heart failure with preserved, mid-range and reduced ejection fraction

BACKGROUND

Evidence of sympathetic and renin-angiotensin-aldosterone system activation provided a rationale for neurohormonal antagonism in heart failure with reduced ejection fraction (HFrEF), while no data are available in patients with milder degree of systolic dysfunction. We aimed to investigate neurohormonal function in HF with preserved and mid-range EF (HFpEF/HFmrEF).

METHODS

Three cohorts (n = 189/each) of stable HFpEF, HFmrEF and HFrEF patients were selected (median age 70, 67 and 67 years; male 56%, 73% and 74%, respectively). Patients received a baseline clinical assessment including plasma renin activity (PRA), aldosterone, catecholamines, and N-terminal fraction of pro-B-type natriuretic peptide (NT-proBNP) assays, and were followed-up for all-cause death.

RESULTS

Neuroendocrine profile was similar between HFpEF and HFmrEF, while all neurohormones except epinephrine were higher in HFrEF than in HFmrEF (NT-proBNP 2332 ng/L, IQR 995-5666 vs 575 ng/L, 205-1714; PRA 1.7 ng/mL/h, 0.4-5.6 vs 0.6 ng/mL/h, 0.2-2.6; aldosterone 153 ng/L, 85-246 vs 113 ng/L, 72-177; norepinephrine 517 ng/L, 343-844 vs 430 ng/L, 259-624; all p < 0.001, epinephrine 31 ng/L, 10-63 vs 25 ng/L, 10-44; p = 0.319). These findings were unrelated to treatment heterogeneity. Ten percent of HFpEF patients had elevated PRA, aldosterone and norepinephrine vs. 8% in HFmrEF and 21% in HFrEF. During a 5-year follow-up, survival decreased with the number of neurohormones elevated (HFpEF: log-rank 7.8, p = 0.048; HFmrEF: log-rank 11.8, p = 0.008; HFrEF: log-rank 8.1, p = 0.044).

CONCLUSIONS

Neurohormonal activation is present only in a subset of patients with HFpEF and HFmrEF, and may hold clinical significance. Neurohormonal antagonism may be useful in selected HFpEF/HFmrEF population.

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.

Criteria for diagnosing primary aldosteronism on the basis of liquid chromatography-tandem mass spectrometry determinations of plasma aldosterone concentration

BACKGROUND

Primary aldosteronism is affecting about 10% of hypertensive patients. Primary aldosteronism should be diagnosed by screening tests based on plasma aldosterone concentration (PAC) and aldosterone-to-renin ratio (ARR), followed by confirmatory test. The cutoff values for PAC and ARR depend on PAC and plasma renin measurement methods. Liquid chromatography-tandem mass spectrometry (LC-MS/MS), the new gold standard method for aldosterone determination, is now widespread but shows lower values than immunoassays. New cutoff values have yet to be determined with LC-MS/MS PAC.

METHODS

In a retrospective cohort, we measured PAC by LC-MS/MS in 93 healthy volunteers, 77 patients with essential hypertension and 82 primary aldosteronism patients (42 lateralized, 24 bilateral, 16 primary aldosteronism without adrenal vein sampling) after 30 min in a seated position.

RESULTS

PAC ranged from 42 to 309 pmol/l in healthy volunteers and from 63 to 362 pmol/l in essential hypertensive patients. A cutoff value of 360 pmol/l for basal PAC had a sensitivity of 90.5% and a specificity of 95.1% to differentiate lateralized primary aldosteronism from essential hypertensive patients. ARR ranged from 2.3 to 22.3 in healthy volunteers and from 3.2 to 55.6 pmol/mU in essential hypertensive patients. Using ROC curves, we selected an ARR of 46 pmol/mU, which provided a sensitivity of 100% and a specificity of 93.4% to distinguish between essential hypertensive and lateralized primary aldosteronism patients (sensitivity 94.4%, specificity 93.9% for the overall primary aldosteronism population).

CONCLUSION

Criteria for primary aldosteronism screening need to be adapted, given the increasing use of LC-MS/MS to determine PAC. We suggest to use 360 pmol/l and 46 pmol/mU as cutoff values, respectively, for basal PAC and ARR after 30 min of seated rest.

Application of 3D-printed scabbard-like sorbent for sample preparation in bioanalysis expanded to 96-wellplate high-throughput format

Modern bioanalysis, which involves the quantitative and qualitative determination of small-molecule endogenous and exogenous substances in biological samples, is a powerful and useful tool that can generate valuable information related to many areas connected with human health and quality of life. Although LC-MS and GC-MS are widely viewed as the gold standards for many bioanalytical tasks, the scientific community has not abandoned its search for newer, more efficient, and more inexpensive methods of performing extraction as a sample preparation step before final analysis. Recent research showing the immense potential of 3D printing compelled our group to explore how this technology could be applied to techniques used in analytical chemistry. In particular, 3D printing offers three promising advantages: availability, low cost of materials and equipment, and the ability to fabricate objects of nearly any shape to suit the needs of a given application. Previously, we demonstrated that a commercial 3D material (LAY-FOMM) can function as a chemically active object that enables the reversible sorption of the antidiabetic drug, glimepiride, and endogenous steroids. In this report, we use a 3D printer to fabricate sorbents with a scabbard-like shape for use with a 96-blade system, which, along with the use of a 96-well plate, allows multiple extractions to be performed simultaneously. In order to assess the relative benefits of this 3D printed approach, we compare the performance of the proposed LAY-FOMM-based sorbent to that of the widely used C18 sorbent. Although the LAY-FOMM sorbent showed lower extraction recovery rates than the C18 sorbent, all of the other validation parameters suggest that it is suitable for use in high-throughput analysis of steroids in human plasma.

Migration from RIA to LC-MS/MS for aldosterone determination: Implications for clinical practice and determination of plasma and urine reference range intervals in a cohort of healthy Belgian subjects

Background

Aldosterone measurement is critical for diagnosis of primary aldosteronism and disorders of the renin-angiotensin system. We developed an LC-MS/MS method for plasma and urinary aldosterone and compared it to our RIA method. We present a reference interval study for a Belgian population.

Methods

68 plasma and 23 urine samples were assayed for as part of a method comparison. For the reference interval study, we enrolled 282 healthy Caucasian volunteers (114 Male: mean age 35 ± 11 y and 168 Female: mean age 42 ± 13 y). A subset of 139 healthy volunteers agreed to a 24-h urine collection. For the method validation, 5 plasma and 8 urine pools were run in triplicate and quadruplicate, respectively, on 3 different days.

Results

Between-run imprecision (CV) was 2.8-5.1% for plasma and 4.5-8.6% for urine, except at the low urine concentration of 2.99 nmol/L where a CV of 15.4% was observed. The limit of quantitation was 0.04 nmol/L for plasma and 6.65 nmol/L for urine. Recoveries, based on spiking experiments into natural matrix, did not differ significantly from 100%. Regression comparisons showed that, on average, RIA generated results were 59% and 11% higher than LC-MS/MS for plasma and urine, respectively. The MS reference interval we propose for plasma aldosterone is 0.07 nmol/L-0.73 nmol/L for women and 0.04 nmol/L-0.41 nmol/L for men. No gender difference was observed for urine aldosterone. The reference interval was determined to be <60.94 nmol/day.

Conclusions

The LC-MS/MS method was validated and reference intervals for plasma and urine were established. A significant bias between RIA and LC-MS/MS was noted.

Endocrine and haemodynamic changes in resistant hypertension, and blood pressure responses to spironolactone or amiloride: the PATHWAY-2 mechanisms substudies

BACKGROUND

In the PATHWAY-2 study of resistant hypertension, spironolactone reduced blood pressure substantially more than conventional antihypertensive drugs. We did three substudies to assess the mechanisms underlying this superiority and the pathogenesis of resistant hypertension.

METHODS

PATHWAY-2 was a randomised, double-blind crossover trial done at 14 UK primary and secondary care sites in 314 patients with resistant hypertension. Patients were given 12 weeks of once daily treatment with each of placebo, spironolactone 25-50 mg, bisoprolol 5-10 mg, and doxazosin 4-8 mg and the change in home systolic blood pressure was assessed as the primary outcome. In our three substudies, we assessed plasma aldosterone, renin, and aldosterone-to-renin ratio (ARR) as predictors of home systolic blood pressure, and estimated prevalence of primary aldosteronism (substudy 1); assessed the effects of each drug in terms of thoracic fluid index, cardiac index, stroke index, and systemic vascular resistance at seven sites with haemodynamic monitoring facilities (substudy 2); and assessed the effect of amiloride 10-20 mg once daily on clinic systolic blood pressure during an optional 6-12 week open-label runout phase (substudy 3). The PATHWAY-2 trial is registered with EudraCT, number 2008-007149-30, and ClinicalTrials.gov, number NCT02369081.

FINDINGS

Of the 314 patients in PATHWAY-2, 269 participated in one or more of the three substudies: 126 in substudy 1, 226 in substudy 2, and 146 in substudy 3. Home systolic blood pressure reduction by spironolactone was predicted by ARR (r²=0·13, p<0·0001) and plasma renin (r²=0·11, p=0·00024). 42 patients had low renin concentrations (predefined as the lowest tertile of plasma renin), of which 31 had a plasma aldosterone concentration greater than the mean value for all 126 patients (250 pmol/L). Thus, 31 (25% [95% CI 17-33]) of 126 patients were deemed to have inappropriately high aldosterone concentrations. Thoracic fluid content was reduced by 6·8% from baseline (95% CI 4·0 to 8·8; p<0·0001) with spironolactone, but not other treatments. Amiloride (10 mg once daily) reduced clinic systolic blood pressure by 20·4 mm Hg (95% CI 18·3-22·5), compared with a reduction of 18·3 mm Hg (16·2-20·5) with spironolactone (25 mg once daily). No serious adverse events were recorded, and adverse symptoms were not systematically recorded after the end of the double-blind treatment. Mean plasma potassium concentrations increased from 4·02 mmol/L (95% CI 3·95-4·08) on placebo to 4·50 (4·44-4·57) on amiloride (p<0·0001).

INTERPRETATION

Our results suggest that resistant hypertension is commonly a salt-retaining state, most likely due to inappropriate aldosterone secretion. Mineralocorticoid receptor blockade by spironolactone overcomes the salt retention and resistance of hypertension to treatment. Amiloride seems to be as effective an antihypertensive as spironolactone, offering a substitute treatment for resistant hypertension.

FUNDING

British Heart Foundation and UK National Institute for Health Research.

Validated low-volume aldosterone immunoassay tailored to GCLP-compliant investigations in small sample volumes

Introduction

Heart failure is well investigated in adults, but data in children is lacking. To overcome this shortage of reliable data, appropriate bioanalytical assays are required.

Objectives

Development and validation of a bioanalytical assay for the determination of aldosterone concentrations in small sample volumes applicable to clinical studies under Good Clinical Laboratory Practice.

Methods

An immunoassay was developed based on a commercially available enzyme-linked immunosorbent assay and validated according to current bioanalytical guidelines of the European Medicines Agency (EMA) and U.S. Food and Drug Administration (FDA).

Results

The assay (range 31.3–1000 pg/mL [86.9–2775 pmol/L]) is characterized by a between-run accuracy from − 3.8% to − 0.8% and a between-run imprecision ranging from 4.9% to 8.9% (coefficient of variation). For within-run accuracy, the relative error was between − 11.1% and + 9.0%, while within-run imprecision ranged from 1.2% to 11.8% (CV). For parallelism and dilutional linearity, the relative error of back-calculated concentrations varied from − 14.1% to + 8.4% and from − 7.4% to + 10.5%, respectively.

Conclusions

The immunoassay is compliant with the bioanalytical guidelines of the EMA and FDA and allows accurate and precise aldosterone determinations. As the assay can run low-volume samples of 40 μL, it is especially valuable for pediatric investigations.

•

Low-volume assay allowing investigations in small sample volumes.

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Assay was validated according to bioanalytical guidelines of the EMA and FDA.

•

Assay is applied in pediatric clinical studies of the LENA project.

•

Obtained data is required for rational, efficient & safe drug therapy in children.

Hypertension: The role of biochemistry in the diagnosis and management

Hypertension is defined as a persistently elevated blood pressure ≥140/90mmHg. It is an important treatable risk factor for cardiovascular disease, with a high prevalence in the general population. The most common cause, essential hypertension, is a widespread disease - however, secondary hypertension is under investigated and under diagnosed. Collectively, hypertension is referred to as a "silent killer" - frequently it displays no overt symptomatology. It is a leading risk factor for death and disability globally, with >40% of persons aged over 25 having hypertension. A vast spectrum of conditions result in hypertension spanning essential through resistant, to patients with an overt endocrine cause. A significant number of patients with hypertension have multiple cardiovascular risk factors at the time of presentation. Both routine and specialised biochemical investigations are paramount for the evaluation of these patients and their subsequent management. Biochemical testing serves to identify those hypertensive individuals who are at higher risk on the basis of evidence of dysglycaemia, dyslipidaemia, renal impairment, or target organ damage and to exclude identifiable causes of hypertension. The main target of biochemical testing is the identification of patients with a specific and treatable aetiology of hypertension. Information gleaned from biochemical investigation is used to risk stratify patients and tailor the type and intensity of subsequent management and treatment. We review the approach to the biochemical investigation of patients presenting with hypertension and propose a diagnostic algorithm for work-up.

Establishment of reference intervals for aldosterone and renin in a Caucasian population using the newly developed Immunodiagnostic Systems specialty immunoassay automated system

BACKGROUND

Measurement of aldosterone and/or renin is essential to aid the differential diagnosis of secondary hypertension, guide strategy for therapeutic management of hypertension and assess adequacy of mineralocorticoid replacement.

AIM

The objective was to establish normative data for aldosterone and renin using the Immunodiagnostic Systems specialty immunoassay system platform in a Caucasian population.

METHODS

Following informed consent, 365 subjects were recruited to this study. Subjects were ambulatory and attended clinic for blood pressure measurement and phlebotomy between the hours of 7:00 and 11:00. Blood pressure was measured according to the 2013 European Society of Hypertension/Cardiology guidelines. The inclusion criteria: age ≥18 years, BMI <30 kg/m(2), non-pregnant, blood pressure <140/90, normal electrolytes and kidney function and not taking prescribed/over the counter medications. Ninety-four subjects were excluded based on these criteria. A total of 271 volunteers (females n = 145), aged 18-65 years formed the reference cohort. Blood for aldosterone/renin was collected into ethylenediaminetetraacetic acid specimen tubes. Samples were kept at room temperature and transported within 30 min of blood draw to the laboratory for immediate processing (centrifugation, separation and freezing of plasma). Plasma was stored at -20℃ prior to analysis on the Immunodiagnostic Systems specialty immunoassay system instrument.

RESULTS

The established reference intervals in an Irish Caucasian population for renin: females: 6.1-62.7 mIU/L, males: 9.0-103 mIU/L, for aldosterone: females: <138-1179 pmol/L, males: <138-670 pmol/L, respectively.

CONCLUSION

This study demonstrates that reference intervals for aldosterone and renin should be gender specific. These automated immunoassays offer rapid stratification of patients with refractory hypertension and will better facilitate the optimization of therapeutic management.