The effect of inadequate drying of blood spots on newborn screening analyte concentrations

BackgroundA critical pre-analytical phase of newborn screening (NBS) testing involves the drying of blood applied to the blood collection devices to form the dried blood spots (DBS). Guidance states that blood applied should be air-dried for a minimum of 3 h. A recent survey highlighted that a number of DBS specimens routinely received into laboratories have a 'crinkled' appearance and that DBS specimens collected in a hospital setting are transported to the laboratory in sealed plastic bags. To date no scientific studies have evaluated aspects of blood drying on DBS NBS analyte concentrations.MethodsWe undertook experiments to recreate 'crinkled' DBS specimens in the laboratory and assess the impact on analyte concentrations. We also assessed the impact of storing collection devices following blood application in hermetically sealed plastic bags to impede the drying process. Experiments were performed using whole blood enriched with thyroid stimulating hormone, immunoreactive trypsinogen, phenylalanine, tyrosine, leucine, methionine, octanoyl-carnitine, decanoyl-carnitine, isovaleryl-carnitine and glutaryl-carnitine to pathophysiological concentrations.Results'Crinkled' DBS specimens produced significantly lower results (mean -15.5%, range -25.1 to -4.7%) for all analytes measured versus air-dried DBS specimens (P < .05). Analyte concentrations obtained from DBS specimens following storage in plastic bags before drying were significantly lower (mean -41.6%, range -60.0 to -27.6%) for all analytes measured (P < .05) versus air-dried DBS specimens.ConclusionResults from this study demonstrate that all DBS specimens with a crinkled appearance and those received in plastic specimen bags should be rejected and a repeat specimen collected to prevent erroneous screening results.