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

Abstract

The patient's hematocrit (HCT) level can adversely affect the analysis results when dried blood spots (DBS) are used for sampling. Volumetric DBS sampling has been proposed to nullify the impact of HCT area bias (spreading area) on DBS by normalizing to a known sample volume. However, this strategy ignores DBS-related parameters such as analyte properties (red blood cell–to-plasma ratio) and HCT recovery bias. With the recent release of fully automated HCT measurement systems for DBS analysis, a broad range of end users are now able to measure and correct a sample's HCT level in a nondestructive manner. These systems permit correction for all known HCT-related impacts on DBS, such as analyte properties, HCT recovery bias, HCT area bias, and venous blood–to-DBS ratio, supporting and accelerating future quantitative DBS applications. However, with these novel tools, new questions arise concerning the normalization of analytical results, the choice of technique (single-wavelength reflectance vs near-infrared spectroscopy), and the DBS card-handling process post sampling. Herein, the necessary considerations for end users are addressed and examples are provided.

Validation of a novel automated system, Fluispotter®, for serial sampling of dried blood spots

“…DBS technology is increasingly being recognized as a valuable alternative to plasma sampling ( 8 ) and is potentially used in different scenarios such as testing for hepatitis C infection ( 9 ) or monitoring of anticancer drugs ( 10 ), screening at-risk populations for various diseases ( 11 ), and general screening ( 12 ). The analytical part has similarly advanced from manual handling of DBS samples to a combination of liquid chromotography-tandem mass spectrometry ( 13 ) and robotic DBS extraction systems allowing a fully automated analytical process of DBS ( 14 ). In the context of classical endocrinology, cortisol is of particular interest for timewise multiple assessments due to the diurnal variation and clinical use of dynamic testing, for example, diagnostic workup for Cushing’s syndrome or adrenal insufficiency.…”

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

“…18 For the UV-Vis-based Hct prediction, on the other hand, a Hct prediction module based on the technology developed by Capiau et al 15,16 was recently incorporated into a fully automated DBS extraction system (CAMAG® DBS-MS 500 HCT system). [19][20][21] This opens the possibility of combining individualized Hct prediction (and correction) with fully automated sample extraction. 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.…”

Alternative Sampling Strategies in Therapeutic Drug Monitoring: Microsampling Growing Toward Maturity

“…In addition, recent work from our group, using a commercially available setup (Büchi), supports the suitability of NIR-based Hct prediction. 18 In another contribution, Luginbühl and Gaugler summarized some key findings related to the use of noncontact-based methods for Hct prediction in DBS, whether based on NIR or on single-wavelength reflectance spectroscopy as previously described by these authors, based on technology initially developed by Capiau et al 15,19–21 These authors also focused on the implementation of automated solutions for DBS handling, and 2 such systems are commercially available as of today: the CAMAG DBS-MS 500 and the Gerstel DBS-A. In addition to fully automated handling of DBS cards, an approach that can be described as “ from card to chromatogram, with no hands-on ”, the integration of noncontact technologies for Hct prediction in these devices allows fully automated determination of and, if required, correction for Hct.…”