Objective: Definition of upper limits for 17 alpha-hydroxyprogesterone (17 alpha-OHP) is important as its measurement is used in screening for congenital adrenal hyperplasia. This study aimed at investigating the cut off concentrations in relation to the day of sample collection.
Methods: 17 alpha-OHP concentration was determined in dried filter paper blood spots taken from cord blood and by heel pricking up to the sixth day of life. A sensitive fluoroimmunoassay (DELFIA) method was used. Samples from 1091 apparently health full term neonates were tested. Samples were separated according to the age of sampling.
Results: The 17 alpha-OHP (nmol/l blood) (median and 97.5th centile) concentrations according to the age of sampling were: cord blood (n = 126) 123.7, 265.6; first day 0-6 hours (n = 30) 49.4, 80.3; 6-12 hours (n = 57) 42.7, 79.8; 12-18 hours (n = 58) 38.1, 62.7; 18-24 hours (n = 67) 28.8, 49.7; second day 24-36 hours (n = 51) 23.6, 43.3; 36-48 hours (n = 63) 19.9, 35.4; third day (n = 200) 10.6, 23.5; fourth day (n = 197) 8.8, 20.8; fifth day (n = 76) 6.4, 18.3; sixth day (n = 166) 6.6, 19.4.
Conclusion: Cord 17 alpha-OHP concentrations were very high as previously described, probably owing to steroid production by fetal adrenal glands. Therefore, cord blood is not useful for screening purposes. Thereafter there is a gradual decline in 17 alpha-OHP median concentrations. A cut off value of 30 nmol/l blood was useful in samples obtained after 48 hours of life. However, cut off values before 48 hours should be adjusted according to the sampling time.