RESUMO
Newborn screening for congenital adrenal hyperplasia (CAH) is performed by measuring the concentration of 17α-hydroxyprogesterone (17-OHP) in dried blood spots. Unfortunately, the level of 17-OHP varies due to multiple factors, and therefore, the false positive rate for the test is a challenge. We analyzed screening data from 2007 to 2015 to determine the effect of seasonal changes and manufacturer kit lot changes on 17-OHP values and on numbers of infants referred. Data from screening 2.2 million infants over a 9-year period indicates that in the NYS during the colder months, daily mean 17-OHP values are higher, more retests are performed, and more infants are referred even though fewer infants are born. The practice of using fixed cutoffs for referring infants for CAH leads to more false positive results in colder months. In addition, there was an overall 10% increase in the daily mean 17-OHP values from the 2 years before and after a manufacturer kit lot change that occurred in November 2013, suggestive of a functional change in the kit at that time. CONCLUSION: Newborn screening programs should be cognizant of seasonal temperature variations and (un)anticipated manufacturer kit changes because they may affect 17-OHP values and CAH referral rates. What is Known: ⢠Newborn screening for congenital adrenal hyperplasia is generally performed by measuring 17α-hydroxyprogesterone (17-OHP) levels in dried blood spots. ⢠17-OHP concentrations are affected by gestational age/weight of infant when specimen is collected, specimen collection time after birth, as well as race and sex of infant. What is New: ⢠Seasonal temperature variations and unanticipated manufacturer kit changes affect 17-OHP levels and consequently referral rates in programs that use fixed cutoffs. ⢠Daily mean 17-OHP is generally higher when the ambient temperature is lower.