Evaluation of volumetric blood collection devices for the measurement of phenylalanine and tyrosine to monitor patients with phenylketonuria

Background: Measurement of dried blood spot (DBS) phenylalanine (Phe) is central to the monitoring of patients with phenylketonuria. However, the volume and hematocrit (Hct) of the blood applied to conventional DBS cards significantly affects analytical results. Volumetric blood collection devices are reported to be more accurate, precise and less prone to Hct effects.Methods: Accuracy, imprecision, effect of blood volume and Hct were evaluated for measurement of Phe and tyrosine using three volumetric devices and compared with the conventional PerkinElmer-226 filter-paper collection devices. i.e. conventional DBS cards. Applicability for use in a clinical laboratory was assessed qualitatively.Results: Blood volume did not impact on the performance of the volumetric devices; however, significant biases were observed with the conventional DBS card. A higher Hct introduced unacceptable bias for Neoteryx-Mitra and conventional DBS card. All devices had a mean relative standard deviation (RSD) <= 4.1 %, except for the Neoteryx-Mitra (<= 6.2 %). Relative to liquid blood, the mean biases of Phe for the various devices were-5.1 (HemaXis-DB10),-7.8 (Capitainer-qDBS),-12.0 (Neoteryx-Mitra) and-32.6 % (conventional DBS card).Conclusions: Introducing volumetric collection devices will overcome the significant pre-analytical issues asso-ciated with conventional DBS collection and improve the biochemical monitoring of patients with PKU.

Automated summary

This study evaluated the accuracy, imprecision, blood volume, and hematocrit effects of using volumetric devices and conventional DBS cards for measuring phenylalanine and tyrosine. The results showed that volumetric devices performed better in terms of accuracy and were less affected by hematocrit compared to the conventional method.