RESUMEN
OBJECTIVE: We aimed at defining the most effective routine immunoassay- or liquid chromatography-tandem mass spectrometry (LC-MS/MS)-determined steroid biomarkers for identifying non-classic adrenal hyperplasia due to 21-hydroxylase deficiency (21-NCAH) in a PCOS-like population before genotyping. METHODS: Seventy PCOS-like patients in reproductive age with immunoassay-determined follicular 17OH-progesterone (17OHP) ≥ 2.00 ng/mL underwent CYP21A2 gene analysis and 1-24ACTH test. Serum steroids were measured by immunoassays at baseline and 60 min after ACTH stimulation; basal steroid profile was measured by LC-MS/MS. RESULTS: Genotyping revealed 23 21-NCAH, 15 single allele heterozygous CYP21A2 mutations (21-HTZ) and 32 PCOS patients displaying similar clinical and metabolic features. Immunoassays revealed higher baseline 17OHP and testosterone, and after ACTH stimulation, higher 17OHP (17OHP60) and lower cortisol, whereas LC-MS/MS revealed higher 17OHP (17OHPLC-MS/MS), progesterone and 21-deoxycortisol and lower corticosterone in 21-NCAH compared with both 21-HTZ and PCOS patients. Steroid thresholds best discriminating 21-NCAH from 21-HTZ and PCOS were estimated, and their diagnostic accuracy in identifying 21-NCAH from PCOS was established by ROC analysis. The highest accuracy was observed for 21-deoxycortisol ≥ 0.087 ng/mL, showing 100% sensitivity, while the combination of 17OHPLC-MS/MS ≥ 1.79 ng/mL and corticosterone ≤ 8.76 ng/mL, as well as the combination of ACTH-stimulated 17OHP ≥ 6.77 ng/mL and cortisol ≤ 240 ng/mL by immunoassay, showed 100% specificity. CONCLUSIONS: LC-MS/MS measurement of basal follicular 21-deoxycortisol, 17OHP and corticosterone seems the most convenient method for diagnosing 21-NCAH in a population of PCOS with a positive first level screening, providing high accuracy and reducing the need for ACTH stimulation test.