Measuring thiamine status in dried blood spots

Background: A reliable and robust method with minimum sample collection requirement for thiamine assay is needed in clinical and research settings. Methods: A simple and robust assay for three vitamers (thiamine, Th; thiamine monophosphate, TMP; and thiamine diphosphate, TDP) using a 6.35-mm dried blood spot (DBS) disc was developed, validated and applied. Results: We were able to quantify accurately thiamine status covering all major vitamers Th, TMP and TDP with acceptable recovery (90%–114%), limit of quantification (TDP: 3.0 nM, TMP and Th: 1.5 nM), linearity (TDP: LOQ 400 nM, TMP and Th: LOQ 50 nM, all R² > 0.99), imprecision (coefficient variation < 4.3% for TDP, <10.0% for TMP and < 12.6% for Th) and stability at −20 °C for up to 42 days. By recruiting 20 healthy participants, we cross compared finger capillary DBS with venous whole blood and venous blood pre-spotted on filter papers. The results demonstrated minimum bias between methods. A preliminary dosing study showed the method had excellent sensitivity after a single dose of supplemental thiamine. Conclusions: We have developed and clinically validated a simple, robust, accurate and sensitive assay for the analysis of thiamine status in DBS, suitable for large-scale population studies.