Fully Automated Optical Hematocrit Measurement from Dried Blood Spots

Abstract

The impact of the hematocrit (HCT) on the dried blood spot (DBS)’s spreading area is one of the most important hurdles, which prevents the full acceptance of quantitative microsampling strategies. Several destructive and non-destructive strategies to assess the HCT from a DBS post-sampling have been presented. Unfortunately, the current methods are either labor-intensive, require a complicated algorithm or are not automatable. Here, we present a novel setup that permits the fully automated reflectance analysis to measure the HCT from a DBS. The underlying principle is based on the concept of the non-destructive single-wavelength HCT measurement. The novel module was embedded within the DBS-MS 500 platform to enable high-throughput analysis of HCT values in combination with automated DBS extraction. The novel setup was assessed and optimized for the probe to card distance, stability, anti-coagulant, spotting volume, scan number, calibration variability, accuracy and precision. It showed excellent inter-day (≤3.7%) and intra-day (≤1.16%) precision as well as high accuracy when analyzing authentic samples (101% ± 7% [range: 87–127%]). Besides, the simple and straightforward application of an HCT correction for DBS was demonstrated during a pharmacokinetic study with diclofenac involving three subjects. Thereby, the sample’s HCT and the HCT impact on the analyte were assessed and compensated. In conclusion, the novel setup enables quantitative analysis of non-volumetric samples in an automated fashion without compromising the concept of cost-effective, minimally invasive sampling.

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

“…This differs from the linear regression proposed by Luginbühl et al – however, that model was set up and evaluated using only a limited number of samples and relying on the correlation coefficient ( r 2 ), without in-depth validation, as performed here. 21 In addition, Capiau et al validated a linear regression model after log–log transformation. 15,16 Although these authors found the model to be statistically non-linear, a linear model was accepted based on the back-calculated values of the calibrators.…”

“…16 Overall, the method's performance was comparable to that of the previously published manual method, except for the precision, which was greatly improved, and with the substantial advantage that the fully automated set-up eliminates any hands-on time. 12,14–16,21…”

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.”…”

Analytical Platforms at Swiss Universities of Applied Sciences

“…In a joint effort between the University of Applied Sciences FHNW, the newborn screening laboratory of the children's Hospital Zürich and CAMAG, a new mass spectrometry-based screening method for amino acids, acylcarnitins, and steroids was developed and implemented (CTI Project: 16898.1 PFLS-LS). [5][6][7]…”