QUALITY OF DRIED BLOOD SPOTS IS AN INTEGRAL COMPONENT OF PROMPT DETECTION OF INBORN ERRORS OF METABOLISM

Abstract

Introduction. Inborn Errors of Metabolism (IEM) are constituted a group of genetic diseases that are associated with defects in the synthesis or catabolism of complex molecules, impaired intermediary metabolism and energy production/utilization processes. The clinical manifestation of IEM is nonspecific, that looks similar to septicemia, and most often occurs in the neonatal period with life-threatening acute metabolic crises. Expanded Newborn Screening (ENS) – a biochemical study of the blood of all newborns without exception with the purpose to identify molecular markers of these diseases proved to be the most effective instrument of early IEM diagnostics. The quality of the biological samples (dried blood spots, DBS) in great extent determines the timing, accuracy, and reliability of the results of biochemical measurements. Obtaining of equivocal results in the case of analysis of poor quality DBS requires repeated laboratory tests, that delays the diagnostic process and postpones the start of specific treatment, which usually results in irreversible damage of the brain and internal organs of the child.
 The aim of this work is to (i) review the first results of the implementation of Expanded Newborn Screening in Ukraine (pilot part of the Baby Screen Project), and to analyze literature data regarding the negative impact of poor quality DBS on laboratory determination of IEM marker substances contents in the specimens, (ii) to characterize the typical errors in blood sampling and drying of blood spots, and (iii) to provide practical recommendations for the proper performance of these procedures.
 Materials and methods. Own data of retrospective analysis of the questionable ENS results was superimposed with dried blood specimens, that were investigated in the Pharmbiotest ENS Lab to outline most common inaccuracies. Based on the comparison of these data with the relevant publications it was formulated the practical recommendations for improving quality of DBS preparation to ensure the accuracy and reliability of laboratory measurements and speed up IEM diagnostics.
 Results. The quality of biomaterial selection is an important part of obtaining reliable results during expanded newborn screening. Capillary blood is collected in the maternity hospital from 48-72 hours (full-term) and for 7-11 days (in preterm babies) after the birth from the heel of babies. In this case, a few drops of blood are applied to a special test card made of filter paper, which is dried and sent to the laboratory. Blood tests are performed using a highly sensitive and accurate method of chemical analysis - tandem mass spectrometry in the laboratory "Pharmbiotest", located in Ukraine. Taking into analysis the low-quality samples lead to questionable results, which requires repeated DBS sampling and re-examining. This proved to be the most common cause of delaying IEM detection, diagnosis establishment, and initiation of treatment, which can be fatal for a child with severe IEM forms.
 Conclusions. Informing healthcare professionals and parents about the current results of laboratory monitoring of dried blood spots quality, typical errors in blood sampling and following on-site procedures and negative consequences of its improper performance, as well as providing clear practical recommendations of how these procedures should be done is a proven way of improving and speeding up IEM diagnostics.