Determination of Biotinidase Enzyme Levels in Umbilical Cord Blood and Comparisons with Dried Blood Spot Testing in Newborns

Aim: Biotinidase deficiency (BD) is an autosomal recessive inherited metabolic disorder caused by enzymatic deficiency.Untreated patients may develop neurologic symptoms, hearing loss, optic atrophy, skin eruptions and/or alopecia.Although cord blood has been explored as a possible sampling type for various newborn screening tests, there is limited data on its use to measure biotinidase activity.In particular, there are no standard reference ranges or established cut-off values for BD detection in cord blood.In this prospective cohort study, we aimed to determine biotinidase activity levels in cord blood samples from newborns and to investigate their comparability with dried blood spot (DBS) measurements.Materials and Methods: This prospective cohort study was conducted between October 2020 and December 2021.Biotinidase activity was measured in umbilical cord blood samples at birth and in DBS samples collected as part of the national screening program.In addition, venous blood samples were taken from 20 newborns who agreed to have their biotinidase activity remeasured from venous blood after six months.Results: This study included 97 newborns, 53 girls (54.6%) and 44 boys (45.4%).Measurements of biotinidase activity in umbilical cord blood revealed an enzymatic deficiency in twenty patients (20%).These 20 patients had normal biotinidase enzyme activities according to their DBS samples.None of the 97 patients had a biotinidase enzyme activity of less than 65 U in their DBS samples.The sensitivity of the cord blood measurement, which was defined as the reference standard compared to the DBS test results, was calculated to be 79.38%. Conclusion:The measurement of biotinidase activity in umbilical cord blood may not be suitable for routine screening due to its high rate of false-positive results and uncertain specificity.