Abstract
Dried blood spots (DBS) have been used in newborn screening (NBS) tests for over 50 years. The Newborn Screening Quality Assurance Program (NSQAP) at the Centers for Disease Control and Prevention (CDC) conducted studies to assess the individual impacts of hematocrit and total-spot volume on characteristics of DBS samples. Per-punch serum volumes decreased 27%, RBC volumes more than doubled, absorption times increased over 300%, and spot diameters decreased marginally between the hematocrits of 40% to 65%. Per-punch serum and RBC volumes decreased logarithmically with lowering total-spot volumes. Patient hematocrit is an uncontrollable variable and inevitably affects the resulting punch from a DBS sample. It may be possible, though, to identify samples that fall outside of an acceptable range by noting certain physical characteristics of the DBS.
Highlights
Newborn screening (NBS) began in the early 1960s when Dr Robert Guthrie developed an assay that used bacterial growth patterns to test small disks of blood-saturated blotter paper for elevated levels of phenylalanine [1]
Within the range of hematocrits that we investigated, higher hematocrits resulted in higher per-punch volumes of whole blood and red blood cell (RBC) but lower per-punch volumes of serum
When hematocrit increased from 40% to 65%, per-punch serum volume decreased by 27%
Summary
Newborn screening (NBS) began in the early 1960s when Dr Robert Guthrie developed an assay that used bacterial growth patterns to test small disks of blood-saturated blotter paper for elevated levels of phenylalanine [1]. Over 50 years later, dried blood spot (DBS) samples are still collected from babies’ heels in much the same way, but the filter paper used is more stringently regulated and NBS testing methods have made dramatic advances. Today’s testing methods are almost exclusively quantitative—requiring a consistent sample volume in order to deliver comparable results—and NBS laboratories rely on the assumption that. Flores conducted the laboratory experiments and data collection. Hall contributed the majority of the writing of the manuscript.
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