Near-infrared-based hematocrit determination of dried blood samples collected by volumetric absorptive microsampling: An in-depth evaluation

Abstract

BackgroundVolumetric absorptive microsampling (VAMS) has gained great interest in the past decade because of its capability to collect a fixed volume of blood independent of the hematocrit (Hct). This alternative microsampling technique tackles the well-known Hct-related area bias, a major issue in conventional partial-punch dried blood spot (DBS) analysis. However, as microsampling typically involves the collection of blood, whereas the ‘gold standard’ matrix used in clinical practice is plasma or serum, a major concern remains: how do we interpret or convert these dried blood microsample-based results? ResultsA method to determine the Hct of a VAMS sample based on non-contact NIR spectroscopy was developed and extensively validated. Using authentic patient samples (n = 102) and a dynamic measurement procedure (turning the VAMS samples in between measurements), accurate (maximum bias of –0.022 L/L) and precise (maximum total imprecision of 10.6 %) Hct determinations were obtained. Sample storage (up till one month at room temperature or lower), operator and lot of VAMS devices did not impact the resulting Hct, confirming the method’s robustness. Significance and noveltyThis is the first non-contact method allowing Hct determination of VAMS samples. Importantly, there is no ‘consumption’ of part of the microsample, which would impact subsequent analysis of target compounds. As one of the issues hampering wide implementation of microsampling is related to interpretation of (dried) blood-based results and conversion into plasma results, a simple and easy way to determine the Hct of a microsample, as presented here, may help to overcome this hurdle.