How Long are Residual Newborn Screening Specimens Useful for Retesting when Stored in Suboptimal and Uncontrolled Conditions of Temperature and Humidity?

Residual DBS specimens from newborns diagnosed with Phenylketonuria, Congenital Hypothyroidism, Cystic Fibrosis, Adrenal Hyperplasia and Galactosemia collected within 1995-2018, stored in cardboard boxes at ambient temperature uncontrolled conditions, were retested for phenylalanine (Phe), thyrotropin (TSH), immunoreactive trypsinogen (IRT), total galactose (TGal) 17-hydroxyprogesterone (17OHP), to demonstrate how long are they stable these conditions useful reconfirm a previous abnormal result. Recovery percentage retesting qualitative interpretation regarding the current cutoff evaluated. Phe, TSH IRT recoveries showed decreasing trends along time. Phe recovery was 64 % after 2-years storage; decayed rapidly recovering 47.3 1-year, while of 60 1-year. Although 17OHP presented wide variation results, decaying trend also found. Results suggest is more than IRT, as supported by > 71 when ≤ 2-years. TGal an erratic behavior, so that it not possible estimate expected concentrations function storage above 100 found UDP-galactose-4-epimerase galactose-1-phosphate uridyltransferase deficiencies, evidencing liberation other sources. These results make very valuable contribution programs storing residual conditions.