The stability of markers in dried-blood spots for recommended newborn screening disorders in the United States.

We aimed to measure separately the contributions of heat and humidity to changes in levels of 34 markers of inborn disorders in dried-blood-spot (DBS) samples. We stored paired sets of DBSs at 37°C for predetermined intervals in low-humidity and high-humidity environments. Marker levels of all samples in each complete sample set were measured in a single analytic run. During the 30 ± 5 day studies, galactose-1-phosphate uridyltransferase and biotinidase lost almost 65% of initial activities in low-humidity storage; most of the degradation in 27 other markers was attributable to adverse effects of high-humidity storage; seven markers in DBSs stored at high humidity lost more than 90% of initial levels by the end of the study and 4 of the 7 lost more than 50% of initial levels within the first week of storage. Minimizing both humidity and temperature in DBS transportation and storage environments is essential to maintaining sample integrity.