Establishing Genomic Reference Intervals for Clinical Haematology Parameters in the Nigerian Population: A Multi-Ethnic Genome-Phenome Study

Reference intervals for haematological parameters currently used in Nigerian clinical practice are largely derived from non-African populations, creating systematic misclassification biases that affect disease diagnosis and population health research, particularly for conditions such as neutropaenia and thrombocytopaenia in African populations. This research establishes genomic and phenotypic reference intervals for comprehensive haematological parameters in a large, multi-ethnic, healthy Nigerian population. A multi-centre, population-based cross-sectional study will recruit 3,000 healthy adult volunteers from all six geopolitical zones, representing 18 major ethnic groups including Hausa, Yoruba, Igbo, Ijaw, Kanuri, Tiv, and Fulani. Full blood count, reticulocyte indices, and immature platelet fraction will be measured on standardised Sysmex XN-series analysers with rigorous internal and external quality control. Genome-wide genotyping on the H3Africa array will identify genetic variants associated with haematological trait variation through GWAS. Reference interval derivation will follow CLSI EP28-A3c and IFCC recommendations, with population stratification by age, sex, and ethnicity. Genetic determinants of the benign ethnic neutropaenia phenotype will be specifically characterised. Original contributions include the most comprehensive Nigerian haematological reference dataset, the first genome-phenome map of haematological traits in the Nigerian population, and ethnicity-specific reference interval recommendations for clinical implementation. Findings will directly improve diagnostic accuracy across all Nigerian healthcare settings and provide a foundational genomic resource for the Nigerian biomedical research community. Keywords: reference intervals, haematology, Nigerian population, genome-wide association, benign ethnic neutropaenia