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

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.

Current Status of Newborn Bloodspot Screening Worldwide 2024: A Comprehensive Review of Recent Activities (2020–2023)

“…For example, several NBS activities that are focused on the NBS laboratory have been described. Primary is the development of a quality assurance (QA) and proficiency testing (PT) program for LATAM screening laboratories, the “External Quality Assurance Scheme for Neonatal Screening” (PEEC-PN—after its Spanish name, “Programa de Evaluación Externa de Calidad—Pesquisa Neonatal ” ), located at the Fundación Bioquímica Argentina [ 1108 ]. Since 2000, participation in the PEEC-PN has steadily increased, improving the quality and harmonization of NBS screening test results across the region.…”

“…The specimens had been stored up to 23 years in suboptimal and uncontrolled conditions of temperature and humidity and were analyzed for Phe, TSH, IRT, TGal, and 17-hydroxyprogesterone (17OHP). The findings were summarized for the benefit of laboratories in resource poor countries who might meet similar specimen storage challenges [ 1111 ].…”

Evaluation of a New Laboratory Protocol for Newborn Screening for Congenital Adrenal Hyperplasia in New Zealand

“…Data from the retrospective analysis of steroid levels in stored NBS samples should be interpreted with caution. It has previously been shown that measurements of 11DF and F are not reliable in bloodspots stored longer than 3 months at room temperature [ 15 ], and 17OHP has shown to be sufficiently stable for at least 2 years for retrospective studies [ 25 ]. We could not identify any similar studies for the long-term stability (>1 year) of 21DF; however, the results were sufficiently informative for the purposes of this study.…”