But it's no longer the only technique you need to know about.
With the numerous advantages of blood microsampling, venipuncture can and should be replaced in some situations. The question is not which blood sampling method gives the best results, but rather how close to the best are test results, obtained from capillary blood via microsampling technique.
The quality of capillary vs. plasma samples are primarily determined by specimen composition rather than blood collection method. Regarding pH and gasses, capillary blood is actually closer to arterial than venous blood. Compared to a venous plasma, capillary plasma contains higher concentrations of proteins, calcium and chloride, and lower levels of potassium, sodium, and urea nitrogen.
When the correlation between test results obtained from capillary blood and venous plasma has been established, capillary blood samples can produce high-quality results. As demonstrated in a study published in European Journal of Clinical Pharmacology, the capillary blood piperaquine measurement could prove useful in field assessment studies of the therapeutic efficacy of malaria treatment. Similarly, a study in American Journal of Clinical Pathology demonstrates the applicability of point-of-care capillary blood testing in international normalized ratio (INR) monitoring programs for POC INR programs.
To avoid poor-quality specimens in research and medicine, it is crucial that the sampling is conducted in accordance with established best practices:
With numerous advantages of blood microsampling, it is tempting to label the technique the best. The fact is, it can be the best in some situations, and a close second in others. However, to enter the debate of capillary blood vs. plasma, rigorous, ongoing quality assurance measures during all stages of a sample cycle are an absolute must.