Dried Blood Spots in Neonatal Studies: A Computational Analysis for the Role of the Hematocrit Effect

Dried blood spot (DBS) microsampling is extensively employed in newborn screening (NBS) and neonatal studies. However, the impact of variable neonatal hematocrit (Ht) values on the results can be a source of analytical error, and the use of fixed Ht for calibration (Htcal) is not representative of all neonatal subpopulations. A computational approach based on neonatal demographics was developed and implemented in R® language to propose a strategy using correction factors to address the Ht effect in neonatal DBS partial-spot assays. A rational "tolerance level" was proposed for the Ht effect contribution to the total analytical error and a safe Ht range for neonatal samples, where the correction of concentrations can be omitted. Furthermore, an "alert zone" for a false positive or negative result in NBS was proposed, where the Ht effect has to be considered. Results point toward the use of Htcal values closely representative of populations under analysis and an acceptable level of percentage relative error can be attributed to the Ht effect, diminishing the probability of correction. Overall, the impact of the Ht effect on neonatal studies is important and future work may further investigate this parameter, correlated to other clinical variables potentially affecting results.

A validated method for the determination of hematocrit in dried blood spots using image analysis

Aim: To develop a nondestructive method for the estimation of hematocrit (HCT) in dried blood spots (DBSs). Materials & methods: Standards and controls were created (HCT range: 0.20-0.50 l/l) and DBS scanned using a flatbed scanner. Gray values and pixel areas were analyzed with open-source software to estimate HCT and volume, respectively. HCT obtained in whole blood using hematological analyzer was compared with DBS scanner method (n = 50). Results: Between-run precision was 4.7-10.2% and between-run accuracy was 89.6-102.1%. In the hematological instrument comparison, 96% of the patient sample results were within ±15%. Conclusion: The nondestructive method can be used to exclude patient DBS samples with extreme HCT levels from further analysis and avoid bias on measured concentration.

Therapeutic Drug Monitoring of Tacrolimus Based on Volumetric Absorptive Microsampling Technique (VAMS) in Renal Transplant Pediatric Recipients-LC-MS/MS Method Development, Hematocrit Effect Evaluation, and Clinical Application

Tacrolimus (TAC) is post-transplant pharmacotherapy's most widely used immunosuppressant. In routine clinical practice, frequent uncomfortable venipuncture is necessary for whole-blood (WB) collection to check trough TAC levels. Volumetric absorptive microsampling (VAMS) is an alternative strategy to WB collection. In this study, we aimed to validate and develop a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for TAC quantification in WB and VAMS samples. After extraction with water and protein precipitation, the samples were directly analyzed using LC-MS/MS. Whole-blood and VAMS capillary-blood samples were collected from 50 patients treated with TAC during the follow-up visits. The cross-correlation between the developed methods was evaluated using Passing-Bablok regression and a Bland-Altman bias plot. The matrix effect (ME) and carry-over were insignificant for both scenarios. There was a high correlation between the processes and no significant clinical deviation. LC-MS/MS methods were successfully developed and validated in the 0.5-60 ng/mL calibration range. This study demonstrated and confirmed the utility of VAMS-based TAC monitoring in the pediatric population. This is the first study to directly develop and validate the VAMS LC-MS/MS method for evaluating the hematocrit effect in the pediatric population. The statistical correlation between immunochemical and VAMS-based methods was satisfactory.

Hematocrit effect on dried blood spots in adults: a computational study and theoretical considerations

Dried blood spots (DBS) are formed by deposition of a small amount of blood on specific adsorbent paper and its physical drying. DBS are employed as a sampling method in several fields of life sciences and drug research. A concern about DBS is the so-called 'Hematocrit (Ht) effect', as a different Ht leads, due to different viscosity, to different spot size, affecting assay bias. Solutions have been proposed, including the correction of quantified concentrations with a suitable correction factor. In order to quantitatively assess Ht impact on the DBS measurements, a computational approach was developed and implemented in R^® language. First, the % relative error was modeled with respect to Ht. Then, Monte Carlo simulations were performed in virtual men/women populations with different Ht levels and the % relative error in relation to the Ht used for calibrators was quantified. An upper level for % relative error being a 'tolerable contribution' of Ht effect to % total analytical error was finally suggested, defining, for the first time, a potential Ht range for analysis of adults' samples, where correction of concentrations of unknown samples may be omitted. Such tolerable level for % relative error may be defined in each laboratory, also based on experimental parameters (type of paper and blood volume). Using a Ht calibration value representing the study population is fully rationalized, leading to reduced probability for concentration corrections. Regulatory criteria for bioanalysis can thus be targeted, moving towards wider utilization of DBS in human pharmacokinetic and clinical trials.

Dried blood spot analysis of (+) and (-) darunavir enantiomers on immobilized amylose tris-(3, 5-dimethylphenylcarbamate) LC and its application to pharmacokinetics

Dried blood spot analysis is an innovative novel blood sampling technique gaining interest in drug discovery and development processes owing to its inherent advantages over the conventional whole blood, plasma or serum sample collection. The present manuscript describes the development and validation of a highly sensitive and precise method of evaluation of pharmacokinetics of (+) and (-) darunavir enantiomers on rat dried blood spots. The enantiomers on rat dried blood spots were extracted into methanol and separated by LC on a Chiralpak IA column using hexane and ethanol containing 0.1% DEA (75:25, v/v) as a mobile phase at 20°C; both the enantiomers were detected at 266 nm using a photodiode array detector. The method was validated in terms of selectivity, linearity, accuracy, precision and stability as per the US Food and Drug and Administration guidelines. The hematocrit effect on extraction recovery was evaluated and the mean recoveries of (-) and (+) enantiomers of darunavir from dried blood spots were found to be 85.76 and 88.91% respectively. The intra- and inter-day precision and accuracy were 3.1-8.4 and 0.8-4.8% respectively. The developed method was successfully applied to a pharmacokinetic study of (+) and (-) enantiomers of darunavir on rat dried blood spots.

Glycemic control in the burn intensive care unit: focus on the role of anemia in glucose measurement

Glycemic control with intensive insulin therapy (IIT) has received widespread adoption secondary to findings of improved clinical outcomes and survival in the burn population. Severe burn as a model for trauma is characterized by a hypermetabolic state, hyperglycemia, and insulin resistance. In this article, we review the findings of a burn center research facility in terms of understanding glucose management. The conferred benefits from IIT, our findings of poor outcomes associated with glycemic variability, advantages from preserved diurnal variation of glucose and insulin, and impacts of glucometer error and hematocrit correction factor are discussed. We conclude with direction for further study and the need for a reliable continuous glucose monitoring system. Such efforts will further the endeavor for achieving adequate glycemic control in order to assess the efficacy of target ranges and use of IIT.