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Hematocrit, blood volume, and surface area of dried blood spots - a quantitative model
Mervat M Alsous1,2,3, Ahmed F Hawwa1,4, James C McElnay1
1Clinical and Practice Research Group, School of Pharmacy, Queen's University Belfast, UK.
Insights
Dried blood spot (DBS) analysis is crucial for pediatric research. This study developed a model showing blood volume significantly impacts DBS surface area more than hematocrit, aiding quality control and error estimation.
Area of Science:
- Clinical chemistry
- Biomedical engineering
- Pediatric research
Background:
- Dried blood spot (DBS) sampling is vital for clinical research, especially in pediatrics.
- Variations in hematocrit and blood volume can affect DBS analyte concentration accuracy.
- Guthrie cards are commonly used for DBS collection.
Purpose of the Study:
- To investigate the impact of hematocrit and blood volume on DBS surface area.
- To develop and validate a model linking these factors to surface area.
- To propose surface area measurement as a quality control metric.
Main Methods:
- ImageJ® software was used to measure blood spot surface area.
- Experiments varied hematocrit levels (25-55%) and blood volumes (7.5-30 μL).
- A validated mathematical model was created.
Main Results:
- Both blood volume and hematocrit influence DBS surface area.
- Blood volume has a greater positive effect on surface area than hematocrit's negative effect.
- The validated model accurately predicts surface area based on volume and hematocrit.
Conclusions:
- Blood spot surface area measurement can serve as a quality control in fixed-volume DBS sampling.
- This method can help estimate unknown hematocrit levels or identify technical errors in blood volume.
- The findings enhance the reliability of pediatric DBS studies.
Abstract:
The use of the dried blood spot (DBS) sampling technique has extended the scope of clinical research, particularly in children. The effects of different hematocrit levels (25-55%) and different blood volumes (7.5-30 μL) on the surface area of the blood spots were investigated using ImageJ® software. Variation in hematocrit levels between patients and inaccuracies in blood volumes applied to Guthrie cards can have a marked effect on analyte concentrations measured in DBS samples. The current study presents a validated model that links blood volume and hematocrit to the surface area of the blood spot. The final model showed that both factors affect the blood spot surface area, however, the positive effect of blood volume is higher than the negative effect of hematocrit. The measurement of surface area could be added as an additional quality control step in clinical studies that have adopted fixed volume DBS sampling for the quantification of the analytes. This approach can be used in estimating the hematocrit if this is not known for a patient or estimating the volume in spots that are visually different in size from the norm, i.e. technical error.
