Urinary pregnanetriol-3-glucuronide excretion in neonates and the use of urinary pregnanetriol-3-glucuronide/creatinine ratio in differentiating 21-hydroxylase deficiency

Introduction: A number of neonatal patients with 21-hydroxylase deficiency (21-OHD) have been discovered since the initiation of a nationwide mass screening program for congenital adrenal hyperplasia (CAH) in Japan. At the same time more than 80% of the referred neonates were found to be free from 21-OHD after detailed examination. Therefore, a simple method for identifying 21-OHD among referred neonates from mass screening or a second screening method for referred neonates is required. Methods: In order to examine whether measurements of pregnanetriol-3-glucuronide (PT-3-G) in a single spot urine enable us to diagnose neonatal patients with 21-OHD. urinary PT-3-G concentrations were measured with our newly developed enzyme-linked immunosorbent assay method in 163 urine specimens from 107 infants and those from 21 referred neonates from a mass-screening program for CAH. Results: Median PT-3-G concentrations in 5-, 6-and 14-day-old infants were 11.5 nmol/l (range: 2.9–85.6, n = 35), 20.1 nmol/l (range: 5.4–89.1, n = 43) and 38.8 nmol 1 (range: 8.9–143.5, n = 34), respectively. Median values of the molar ratio of PT-3-G to excreted creatinine (PT-3-G, creatinine; × 105) were 0.82 (range: 0.23–2.95), 1.2 (range: 0.40–6.5) and 3.7 (range: 0.92–8.2). respectively. Both concentrations and ratios increased significantly with age (5 days vs. 6 days: P < 0.001 for the concentrations, P < 0.01 for the ratios; 6 days vs. 14 days: P < 0.01 for the concentrations, P < 0.001 for the ratios). Seven of the 21 neonates were diagnosed with 21-OHD, while the remaining 14 neonates did not have this disease. PT-3-G concentrations and the ratios in the 14 false-positive cases ranged from 21.2 to 909 nmol/l and 1.7 to 28.0. Those in the 7 diagnosed patients ranged from 1161 to 2814 nmol/l and 81.4 to 365, respectively. Discussion: Neither value overlapped between the patients and the false-positive cases. Therefore, measurement of urinary PT-3-G was a useful method of detecting neonates with 21-OHD among referred neonates. However, the ratios appeared to be more useful than concrete concentrations in distinguishing the neonates with 21-OHD.