Remote HbA_1c testing via microsampling: fit for purpose?

The collection of capillary blood microsamples via finger-prick has several advantages over traditional blood collection. It is considered convenient and more patient-centric, enabling collection of the sample by the patient at her/his home with subsequent analysis in the lab following postal shipment. Determination of the diabetes biomarker HbA_1c in self-collected microsamples to remotely monitor diabetes patients seems to be a very promising option which could eventually lead to better treatment adaptations and disease control. This is especially convenient/relevant for patients living in areas where venipuncture is impractical, or to support virtual consultations using telemedicine. Over the years, a substantial numbers of reports on HbA_1c and microsampling have been published. However, the heterogeneity of the applied study designs and data evaluation is remarkable. This review provides a general and critical overview of these papers, along with specific points of attention that should be dealt with when aiming at implementing microsampling for reliable HbA_1c determination. We focus on the used (dried) blood microsampling techniques, collection conditions, stability of the microsamples, sample extraction, analytical methods, method validation, correlation studies with conventional venous blood samples and patient satisfaction. Lastly, the possibility of using liquid instead of dried blood microsamples is discussed. Liquid blood microsampling is expected to have similar advantages as dried blood microsampling and several studies suggest it to be a suitable approach to collect samples remotely for subsequent HbA_1c analysis in the lab.