Effect of blood volume on analytical bias in dried blood spots prepared for newborn screening external quality assurance.

Abstract

Aim: Dried blood spots (DBS) are used for the analysis of more than 2000 biomarkers. We assessed a range of analyte concentrations and diameters of DBS. Materials & methods: DBS samples were created by the application of increasing volumes of whole blood prepared by the UK NEQAS Quality Assurance Laboratory. Samples were analyzed in four separate laboratories. Results: Volumes less than 25μl (8mm) and more than 75μl (14mm) created unsatisfactory analytical biases. Results obtained from peripheral subpunches tended to be higher than those from a central subpunch. Conclusion: DBS diameters formed from nonvolumetric application of blood to filter paper can be used to assess whether measurement bias will be within acceptable limits according to the analyte being quantified. DBS received for newborn screening in the UK with diameters less than 8mm and those more than 14mm should be rejected.