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