Influence of spironolactone on neonatal screening for congenital adrenal hyperplasia

Spironolactone metabolite causes falsely increased progesterone in the Abbott Architect immunoassay

BACKGROUND

Immunoassays are important for routine clinical testing and medical diagnosis. However, they are limited by cross-reactivity especially at low analyte concentrations. There is a critical need to investigate compounds that can interfere with immunoassays. Herein, we describe the identification of canrenone, a spironolactone metabolite that falsely increases progesterone concentrations on the Abbott Architect i2000 Immunoassay.

METHODS

Serum samples and assay diluents were spiked with spironolactone or canrenone and progesterone concentrations were measured on the Architect i2000 and Immulite XPi immunoassay platforms. Blood samples from patients taking spironolactone were analyzed with liquid chromatography-tandem mass spectrometry to evaluate the intrinsic response of progesterone concentrations to the presence of canrenone.

RESULTS

We measured approximately 10-fold higher progesterone concentrations on the Abbott Architect i2000 compared to reference immunoassay analyzers (Siemens Immulite XPi and Roche Cobas e601/602), suggesting an analytical error which is unique to the Architect i2000 antibody and/or assay conditions. By measuring serum progesterone after addition of spironolactone or canrenone to serum samples, we found that canrenone falsely increased progesterone on the Architect i2000 immunoassay. However, this interference was more pronounced at low serum progesterone concentrations. Moreover, a strong positive correlation was seen between canrenone and measured serum progesterone concentrations.

CONCLUSIONS

Our investigations are important for individuals who require progesterone measurements using the Architect i2000 immunoassay, especially because it is unlikely for clinicians to order canrenone measurements alongside progesterone measurements for individuals taking spironolactone. Further research is needed to determine whether canrenone can influence progesterone measurements on other immunoassay systems.

Spironolactone dose‑dependently alleviates the calcification of aortic rings cultured in hyperphosphatemic medium with or without hyperglycemia by suppressing phenotypic transition of VSMCs through downregulation of Pit‑1

Vascular calcification (VC) is highly prevalent in chronic kidney disease (CKD), especially in patients with end stage renal disease and is strongly associated with cardiovascular morbidity and mortality. Clinical observations have demonstrated that hyperphosphatemia and hyperglycemia can accelerate VC. Spironolactone (SPL) has been proven to improve cardiovascular outcomes in clinical trials and its protective effect on VC has been reported recently; however, the underlying mechanisms are not completely understood and require further investigation. Furthermore, the current CKD rat models that are used to research VC do not match well with the clinical characteristics of CKD patients. Aortic rings were obtained from male Sprague-Dawley rats, then cultured in different media with varying phosphorus and glucose concentrations to investigate the effects and the possible mechanisms, as well as the effective serum concentrations of SPL, on VC and type III sodium-dependent phosphate cotransporter-1 (Pit-1) expression. SPL dose-dependently alleviated VC by suppressing the phenotypic transition of vascular smooth muscle cell (VSMCs) through downregulation of Pit-1 in a high phosphorus medium and even in a high phosphorus combined with high glucose medium. The combined effects of hyperglycemia and hyperphosphatemia on the calcification of aortic rings ex vivo were demonstrated. In conclusion to the best of our knowledge, this article is the first report on the effective serum concentrations of SPL capable of protecting VSMCs from calcification and provides the first experimental evidence for the combined effects of hyperglycemia and hyperphosphatemia on VC of aortic rings. Additionally, the Pit-1 protein level may be a novel index for evaluating the magnitude of VC in CKD patients.

Diuretics acting on the distal renal tubule for preterm infants with (or developing) chronic lung disease

BACKGROUND

Lung disease in preterm infants is often complicated with lung edema.

OBJECTIVES

To assess the risks and benefits of diuretics acting on distal segments of the renal tubule (distal diuretics) in preterm infants with or developing chronic lung disease (CLD).

SEARCH STRATEGY

The standard method of the Cochrane Neonatal Review Group were used. Initially, MEDLINE (1966 to November 2001), EMBASE (1974 to November 2001) and the Cochrane Controlled Trials Register (CENTRAL,The Cochrane Library, Issue 4, 2001) were searched. In addition, several abstract books of national and international American and European Societies were hand searched. Updated searches in April 2003, April 2007, and December 2010 did not yield any additional trials.

SELECTION CRITERIA

Included in this analysis are trials in which preterm infants with or developing CLD and at least five days of age were randomly allocated to receive a diuretic acting on the distal renal tubule. Eligible studies needed to assess at least one of the outcome variables defined a priori for this systematic review.

DATA COLLECTION AND ANALYSIS

The standard method for the Cochrane Collaboration described in the Cochrane Collaboration Handbook were used. Two investigators extracted, assessed and coded separately all data for each study. Any disagreement was resolved by discussion. Parallel and cross-over trials were combined. Whenever possible, baseline and final outcome data measured on a continuous scale was transformed into change scores using Follmann's formula.

MAIN RESULTS

Of the six studies fulfilling entry criteria, most focused on pathophysiological parameters and did not assess effects on important clinical outcomes defined in this review, or the potential complications of diuretic therapy.In preterm infants > 3 weeks of age with CLD, a four week treatment with thiazide and spironolactone improved lung compliance and reduced the need for furosemide. A single study showed thiazide and spironolactone decreased the risk of death and tended to decrease the risk for remaining intubated after eight weeks in infants who did not have access to corticosteroids, bronchodilators or aminophylline.

AUTHORS' CONCLUSIONS

In preterm infants > 3 weeks of age with CLD, acute and chronic administration of distal diuretics improve pulmonary mechanics. However, positive effects should be interpreted with caution as the numbers of patients studied are small in surprisingly few randomized controlled trials.

Spironolactone interference in the immunoassay of androstenedione

Background

In an evaluation of androstenedione results from patient serum samples using the Siemens Immulite 2500 analyser and manual Coat-A-Count (CAC) methods, three outliers were evident with grossly elevated results in the CAC assay.

Methods

The clinic notes of three patients with apparently high serum androstenedione concentrations by the CAC assay were checked for medications. The samples were all from patients with polycystic ovary syndrome taking 100–200 mg/d of a steroidal antiandrogen (spironolactone). Two other patients on 50 mg spironolactone per day had less markedly higher androstendione results with the CAC assay. In a further five patients who were selected since they were on spironolactone and had high androstenedione results by the CAC method, spironolactone was temporarily withdrawn and fresh blood samples obtained for analysis.

Results

Spironolactone treatment was associated with higher androstenedione concentrations measured by the CAC assay that reverted to normal on treatment withdrawal. Based on a single test with spironolactone at 1000 ng/mL, the manufacturer reported only 0.109% interference in the CAC assay.

Conclusions

Spironolactone (and/or its metabolites) may interfere in the Siemens CAC assay for androstenedione but not in the Immulite 2500 assay. This experience highlights the need for information from clinicians on drug treatment when laboratory investigations are requested. Drug interferences in immunoassay are common and need evaluation beyond tests performed to certify laboratory reagents.

21-hydroxylase deficiency congenital adrenal hyperplasia

CONONGENITAL ADRENAL hyperplasia (CAH) is an inborn error of metabolism that can produce life-threatening disease in the first one to three weeks of life, unless properly diagnosed and managed. This autosomal recessive disease results in insufficient biosynthesis of cortisol due to an enzyme defect in the adrenal gland. CAH due to 21-hydroxylase (21-OH) deficiency is found in 1/11,000–1/15,000 people in the general population, with a prevalence as high as 1/750 people in some populations such as the Yupik Eskimos in Alaska and the people of La Réunion in France.1 Males and females are equally affected by this disease due to the autosomal recessive pattern of inheritance.

Multiple positive results during a neonatal screening program: a retrospective analysis of incidence, clinical implications and outcomes

AIMS

Neonatal screening programs perform different screening tests on the same blood-spot sample collected on a Guthrie card. We retrospectively investigated the incidence of multiple positive results as well as the outcomes and the physical characteristics of newborns with more than one positive result for phenylketonuria (PKU), congenital hypothyroidism (CH) and congenital adrenal hyperplasia (CAH).

METHODS

Neonatal screening was performed on blood-spot for PKU (phenylalanine concentration by fluorescent ninhydrine method), for CH (simultaneous total thyroxin (tT4) and thyroid-stimulating hormone (TSH) levels by fluoroimmunometric assay); and for CAH (17-hydroxyprogesteron level by fluoroimmunometric assay).

RESULTS

During three years of screening, 39 newborns (37 preterms) showed multiple positive results at screening tests (incidence 1:6387). The most frequent positive results were the combinations of CH and CAH (25/39) and PKU and CH (12/39). At recall, only two newborns were confirmed positive and each for only one disease: one, premature baby, for PKU from the PKU and CH combination; the other, born at term, for CAH from the CH and CAH combination.

CONCLUSIONS

Multiple positive results are a rare observation at neonatal screening for PKU, CH and CAH, more frequently observed in preterm babies. However, multiple positive results must not be overlooked because of true positive results at recall.