Delayed Processing of Chilled Whole Blood for 24 Hours Does Not Affect the Concentration of the Majority of Micronutrient Status Biomarkers.

Background The measurement of micronutrient status is essential to understand the health of individuals and populations, but there are limited data on the stability of micronutrients in whole blood. Objective The objective was to investigate the effect of delayed processing of whole blood on the stability of 25 micronutrient and selected clinical biomarkers. Methods Blood from 16 healthy adults was collected into ethylenediaminetetraacetic acid (EDTA), lithium heparin (LH) or serum tubes. Samples were processed within 2 hours of collection "2-hour processed") or mailed overnight (boxed with frozen cold packs) before processing ("24-hour processed"). Micronutrient and clinical biomarker concentrations were quantified with validated methods. Concentration % difference between the 2- and 24-hour processed samples was calculated and was compared against quality specifications determined from intra- and inter-individual variation. Results All analytes had a sample type where the % difference concentration between 2-hour and 24-hour processed samples was ≤ 4% and that was acceptable based on calculated limits, including for biomarkers of vitamin A, vitamin D, thiamin, folate, vitamin B-12, iron (ferritin) and zinc status, and selected clinical markers, C-reactive protein, HDL and total cholesterol, and triglycerides. EDTA plasma vitamin C was (geometric mean (95% CI)) 43% (36, 49%) lower compared to the 2-hour processed sample. Pyridoxal-5-phosphate (vitamin B-6 biomarker) decreased, with differences from the 2-hour processed samples of -8% (-13, -2%) and -14% (-18, -9%), in LH plasma and serum, respectively. Conclusions In blood collected from adult participants, delayed processing of chilled, whole blood for 24 hours did not materially affect the measured concentrations of the majority of micronutrient and selected clinical biomarkers. This suggests that for these analytes, adherence to a 2-hour processing protocol may be unnecessary. This knowledge is valuable and may help to simplify logistics for sample transport and processing of blood samples for micronutrient status assessment.