The interpretation of bloodspot 17 alpha-hydroxyprogesterone levels in term and pre-term neonates

Bloodspot 17 alpha-hydroxyprogesterone, plasma cortisol, plasma sodium and urinary 17 alpha-hydroxyprogesterone, cortisol, sodium and creatinine levels were determined in 24 term and 32 pre-term infants on the third, eighth and fourteenth days of life. Pre-term infants, whether 'well' or 'sick', had significantly raised bloodspot 17 alpha-hydroxyprogesterone levels (up to 158 nmol/L) compared with those found in term infants (up to 18.8 nmol/L). Urinary 17 alpha-hydroxyprogesterone creatinine ratios were also higher in pre-term infants. Plasma cortisol results showed similar ranges for term and pre-term infants, and bloodspot 17 alpha-hydroxyprogesterone/plasma cortisol ratios for day 3 specimens correlated with the degree of prematurity. These results may be due either to immature enzyme systems in the pre-term baby or to an excess of related steroids cross-reacting in the 17 alpha-hydroxyprogesterone assay. We propose the use of two distinct upper limits of normal of 20 nmol/L (term infants) and 200 nmol/L (pre-term infants), for the interpretation of bloodspot 17 alpha-hydroxyprogesterone levels at the end of the first week of life.