Establishing population-based reference intervals for hematological parameters among apparently healthy adults in Northwest Ethiopia, 2023

Ethiopian diagnostic facilities currently use Western hematological reference ranges, lacking national standardization. This study establishes hematological reference values for healthy adults in Northwest Ethiopia through a population-based cross-sectional study conducted from June to August 2023. Whole blood samples from 759 participants were analyzed using the Siemens ADVIA-560 hematology analyzer. Data were processed with Stata 17.0, and reference intervals (RIs) were calculated for the central 95% of the distribution, with gender & altitude differences assessed via the Mann-Whitney U test (p < 0.05). Sex and altitude based partitioning was done using Harris & Boyd’s Z-test and Lahti et al.’s proportion criteria. Results showed significant variations by sex and altitude, with males exhibiting higher median values for several hematological parameters. The combined 95% reference intervals (RIs) were: WBC (3.11–9.89 × 10⁹/L), NEU (0.96–6.54 × 10⁹/L), LYM (0.69–2.89 × 10⁹/L), MON (0.31–1.46 × 10⁹/L), and BAS (0.05–0.42 × 10⁹/L), with corresponding differential percentages also established. Sex-specific RIs were defined for key parameters. In men: RBC (4.54–6.39 × 10¹²/L), HGB (13.68–19.21 g/dL), HCT (41.39–57.01%), MCHC (32.01–34.91 g/dL), and PLT (127.10–367.10 × 10⁹/L); and in women: RBC (4.17–5.55 × 10¹²/L), HGB (12.51–16.39 g/dL), HCT (37.91–48.89%), MCHC (31.51–34.70 g/dL), and PLT (146.22–411.00 × 10⁹/L). Altitude-based stratification further revealed higher values at high altitude. In men, monocytes, eosinophils, RBC, HGB, HCT, and PLT were elevated, while in women, higher values were observed for neutrophils, monocytes, basophils, HGB, HCT, MCV, and MCH. These findings demonstrate that hematological reference intervals vary by sex and altitude among healthy adults in Northwest Ethiopia. The study highlights the potential value of using locally derived and context-specific reference intervals to improve interpretation of laboratory results. Further multicenter validation studies across diverse Ethiopian populations are recommended to support their application in clinical practice and research.