Introduction. Patient-related variables, such as physical exercise, stress and fasting status are important sources of variability in laboratory testing. However, no clear indications about fasting requirements exist for routine hematological testing, nor the influence of meals were previously assessed.
Methods. Seventeen healthy volunteers consumed a light meal, containing a standardized amount of carbohydrates, protein and lipids. Blood sampling for routine hematological testing was performed before the meal and 1, 2 and 4 hours thereafter.
Results. One hour after the meal, neutrophils and mean corpuscular hemoglobin (MHC) significantly increased, whereas lymphocytes, monocytes, red blood cells distribution width (RDW), hematocrit, mean corpuscular volume (MCV) significantly decreased. A clinically significant variation was only observed for lymphocytes. Two hours after the meal, a significant increase was observed for neutrophils and MCH, whereas lymphocytes, eosinophils, hemoglobin and hematocrit significantly decreased. Clinically significant variations were recorded for lymphocytes, red blood cells (RBC), hemoglobin, hematocrit and MCH. Four hours after the meal MCH was significantly increased, while lymphocytes, eosinophils, RBC, hemoglobin and hematocrit significantly decreased. Clinically significant variations were recorded for neutrophils, eosinophils, RBC, hematocrit and MCH.
Conclusion. The significant variation of several hematological parameters after a light meal demonstrates that the fasting time needs to be carefully considered when performing hematological testing, to allow appropriate interpretation of test results.
Key Words: Fasting, Hematological testing, Meal, Preanalytical variability.