Fully automated correction for the hematocrit bias of non-volumetric dried blood spot phosphatidylethanol analysis

Current evolutions, applications, and challenges of phosphatidylethanol analysis for clinical and forensic purposes

“…The use of DBS sampling in combination with DBS autosamplers overcomes some of the aforementioned challenges and permits fully automated analysis of PEth in combination with nondestructive HCT assessment and correction, using single‐wave reflectance spectroscopy, within about 5 min per sample (Luginbühl, Fischer, et al, 2020; Luginbühl, Gaugler, et al, 2019; Luginbühl, Stöth, et al, 2020). This represents a significant advantage, as large batches of samples can be processed in a fully automated manner, “from card to chromatogram, with no hands‐on.”…”

“…The latter is not easy to obtain in routine practice and might be less preferred. Alternatively, one can estimate the erythrocyte fraction of the whole blood by measuring (or predicting) the HCT (in conventional blood samples or in dried blood samples), followed by a normalization of the PEth concentrations by applying certain correction algorithms (Luginbühl, Stöth, et al, 2020), similar to the analysis of creatinine in urine and the normalization of analyte concentrations thereafter (Cone et al, 2009; Viau et al, 2004). Thereby, a decision has to be made on how to reference the HCT values for PEth: For example, there is the possibility to define HCT intervals in which obtained results are “acceptable” and do not require any HCT‐related conversion, to reference to a common HCT for all samples (e.g., 40%), or to reference to the gender mean, with the normal range for male subjects at 40.7%–50.3% (Kehat et al, 2003) being distinct from that of female subjects at 36.1%–44.3% (Groves et al, 2016).…”

“…For PEth, to the best of our knowledge, no matrix‐based working calibrators are commercially available yet and only a very limited range of proficiency testing programs and materials is available that could serve for quality control purposes. ACQ Science sells authentic and spiked PEth blood samples (Luginbühl, Stöth, et al, 2020), Equalis AB has a proficiency testing program for PEth in liquid blood (Beck et al, 2021), and Arvecon (which organizes proficiency tests on behalf of and in cooperation with the German Society of Toxicological and Forensic Chemistry [GTFCh]) lists an upcoming PEth proficiency study on their webpage.…”

Addressing New Possibilities and New Challenges: Automated Nondestructive Hematocrit Normalization for Dried Blood Spots

“…The direct alcohol marker phosphatidylethanol is an example of such an analyte; it accumulates in the RBC fraction, showing a linear HCT dependence and yields the same results via venous blood analysis and capillary DBS analysis. 23,24 When preparing and measuring an HCT calibration from authentic samples containing the analyte (mixing RBC fraction and plasma), the analyte's HCT dependency can be assessed and normalized together with HCT area and recovery biases. However, this approach does not compensate for differences between venous blood analysis and capillary blood DBS analysis.…”

In-depth evaluation of automated non-contact reflectance-based hematocrit prediction of dried blood spots

“…An initial evaluation of the module by Luginbühl et al yielded promising results 21 and a first application was to use the obtained Hct values to perform a Hct correction of phosphatidylethanol concentrations in DBS. 22 However, as these evaluations only encompassed a limited number ( n = 6) of non-clinical samples, it remained to be demonstrated whether automated reflectance-based Hct prediction of DBS can robustly and universally generate reliable results. In addition, it remained unclear whether each end-user would be required to individually set up and validate their own calibration model (which would limit the potential of routine implementation), and to what extent measurement or DBS variables may impact the result.…”