Full Blood Count Reference Ranges for Apparently Healthy Adults in Port Harcourt, Rivers State, South South Nigeria

This study establishes full blood count (FBC) reference ranges for apparently healthy adult residents of Port Harcourt, Rivers State, located in Nigeria's South South geopolitical zone. Locally derived haematological reference values are critical for accurate clinical interpretation, as population-specific differences in diet, altitude, genetics, and environmental exposure can cause significant deviations from values established in other populations. A cross-sectional descriptive study recruited 500 apparently healthy adults aged 18 to 65 years from three tertiary institutions and two community health centres in Port Harcourt, after excluding individuals with chronic illness, recent blood transfusion, or known haematological disorders. Blood samples were analysed using a calibrated automated haematology analyser. Reference intervals were calculated using the non-parametric method at the 2.5th and 97.5th percentiles, stratified by sex and age group. Male participants showed significantly higher haemoglobin, red blood cell count, and haematocrit values compared to females. Platelet counts were higher in females, consistent with previously reported sex-related differences. White blood cell counts were lower than European reference values across both sexes, a finding consistent with the benign ethnic neutropenia phenomenon documented in African populations. These locally derived reference ranges provide a foundation for improving diagnostic accuracy at hospitals in Rivers State and are recommended for adoption in laboratory quality assurance programmes across South South Nigeria. Keywords: full blood count, reference ranges, healthy adults, Port Harcourt, haematology.