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Influence of spironolactone on neonatal screening for congenital adrenal hyperplasia
I Terai1, K Yamano, N Ichihara
1Division of Clinical Pathology, Hokkaido Institute of Public Health, Sapporo 060, Japan. terai@iph.pref.hokkaido.jp
Aim:
To determine if the diuretic spironolactone cross reacts with 17alpha-hydroxyprogesterone (17OHP) in an enzyme linked immunosorbent assay (ELISA) kit used for the mass screening of congenital adrenal hyperplasia.
Methods:
Concentrations of 17OHP on a blood filter paper disc were measured using an ELISA kit (kit C-7: ENZAPLATE N-17alpha -OHP-7; Chiron, Tokyo, Japan). The cross reactivity of spironolactone and its metabolites with 17OHP was determined. The concentrations of spironolactone and its metabolites in blood were measured using HPLC (high performance liquid chromatography).
Results:
Spironolactone cross reacted with 17OHP using kit C-7 (0.01%), by increasing 17OHP concentration in a dose dependent manner. The blood concentration of spironolactone and its metabolites was nearly 900 ng/ml, high enough to show an additive effect on the 17OHP concentration. About 12% of the false positive cases screened using the kit were due to the administration of spironolactone.
Conclusions:
Spironolactone interferes with 17OHP concentrations, leading to false positive test results for CAH.