Reassessment of predictive values of ACTH-stimulated serum 21-deoxycortisol and 17-hydroxyprogesterone to identify CYP21A2 heterozygote carriers and nonclassic subjects.

ABSTRACT

INTRODUCTION: Heterozygotes (HZs) for 21-hydroxylase deficiency (21OHD) are highly prevalent, ranging from 160 to 111 for classic and nonclassic (NC) forms, respectively. Detection of HZ and asymptomatic NC by CYP21A2 genotyping is valuable for genetic counselling, but costly, complex and narrowly available. Adrenocorticotropic hormone (ACTH)-stimulated serum 17-hydroxyprogesterone (17P) and 21-deoxycortisol (21DF) discriminate 21OHD phenotypes effectively, notably if measured simultaneously by liquid chromatography-tandem mass spectrometry (LC-MS/MS). OBJECTIVE: This study was performed to reassess former LC-MS/MS-defined post-ACTH 21DF, 17P and cortisol (F) cutoffs in family members at risk for 21OHD. DESIGN AND PATIENTS Prospective study in which we screened 58 asymptomatic relatives from families with 21OHD patients and compared post-ACTH steroid phenotypes with subsequent genotypes. RESULTS: Post-ACTH 21DF, 17P, F and (21DF + 17P)/F ratio segregate NC, HZ and wild-type (WT) phenotypes (subsequently genotyped) with some overlap. New receiver operating characteristic curve-defined cutoffs for post-ACTH 21DF, 17P and (21DF + 17P)/F ratio are 60 ng/dl, 310 ng/dl and 12 (unitless). Twenty-six of 33 HZ and all 6 NC (82.1%) had post-ACTH 21DF > 60 and 17P > 310 ng/dl, whereas 17/19 WT (89.5%) had values below cutoffs. Post-ACTH 21DF and 17P had a strong positive correlation (r = .9558; p < .001). A (21DF + 17P)/F ratio > 12 correctly identified 36 of 39 HZ plus NC (92.3% sensitivity) with 84.2% specificity (16 of 19 WT). Given the high frequency of 21OHD HZ, the negative prediction of ratio values below 12 excludes heterozygosity in 99.8% and 99.1% for classic and NC mutations, respectively. CONCLUSIONS: Reassessed ACTH-stimulated 21DF and 17P cutoffs by LC-MS/MS (60 and 310 ng/dl, respectively) correctly recognised 82.5% HZ plus NC, but combined precursor-to-product ratio ([21DF + 17P]/F) cutoff of 12 was superior, identifying 92.3% HZ plus NC. Since one WT subject is an outlier (potential HZ), these values would be somewhat better reinforcing their utility for screening asymptomatic relatives at risk for 21OHD.