Preanalytical phase: Effects of water ingestion during fasting on routine hematological parameters in a small cohort of young women.

BACKGROUND: We analyze the effects of water ingestion before blood extraction on routine hematological parameters. METHODS: Twenty female volunteers -mean 24 y- were included. Blood was collected after a 12 h fast period (T0) and 1 h after the ingestion of 300 ml water (T1). These parameters were analyzed: white blood cell (WBC) count; WBC differential count including lymphocytes (LYM), monocytes (MONO), neutrophils, eosinophils (EOS), and basophils; red blood cell (RBC) count; hematocrit (HCT); hemoglobin (HGB); mean cell volume; mean cell hemoglobin; RBC distribution width; and platelet count (PLT). Statistical significance: P < 0.05. Mean difference % (MD%) was calculated for each parameter and was compared with reference change value (RCV). A change was considered clinically significant when MD% exceeded the RCV. RESULTS: Significant differences were observed in (medians, T0 vs T1, P): WBC ×109/l (6.51 vs 6.12, 0.002); LYM ×109/l (2.90 vs 2.19, 0.000); MONO ×109/l (0.50 vs 0.48, 0.031); EOS ×109/l (0.17 vs 0.16, 0.003); RBC ×1012/l (4.46 vs 4.40, 0.024); HCT l/l (0.38 vs 0.37, 0.036); HGB g/l (129 vs 129, 0.009). All MDs% were lower than their respective RCV. CONCLUSION: Ingestion of 300 ml water 1 h before blood extraction does not alter the hematological parameters studied.