Haemorheological Reference Intervals in Sub-Saharan African Populations: A Critical Appraisal of Methodological Standardisation, Ethnic Variability, and Clinical Application

Abstract

Reference intervals, the statistically defined ranges of physiological parameter values expected in a healthy reference population, constitute a cornerstone of clinical laboratory medicine. In haemorheology, reference intervals for whole blood viscosity, plasma viscosity, erythrocyte deformability, and red cell aggregation index underpin the diagnosis of rheological pathology, guide therapeutic decisions in conditions associated with abnormal blood flow properties, and serve as comparative baselines in clinical research. However, the validity of haemorheological reference intervals depends critically upon their derivation from appropriately characterised reference populations, using standardised and reproducible measurement methodologies under rigorously controlled pre-analytical conditions. In sub-Saharan Africa, where the prevalence of haemoglobinopathies, infectious diseases, nutritional deficiencies, and other conditions that perturb blood rheology is among the highest in the world, the absence of regionally validated, ethnically representative haemorheological reference intervals constitutes a significant gap with direct consequences for clinical practice and research validity. This critical appraisal examines the methodological, biological, and clinical dimensions of haemorheological reference interval derivation in sub-Saharan African populations, with particular focus on Nigeria. We analyse the principal sources of rheological variability in these populations: haemoglobin genotype distribution, endemic infectious disease burden, nutritional status, demographic characteristics (age, sex, body mass), and environmental factors (altitude, temperature, hydration), and critically evaluate the extent to which existing reference interval studies have adequately controlled for these variables. We review the technical standards required for reproducible viscometry, ektacytometry, and aggregometry, and assess the degree to which published sub-Saharan African haemorheological data meet these standards. We then propose a methodological framework for establishing robust, population-specific haemorheological reference intervals suitable for clinical application in high-burden African settings, and identify priority research areas for advancing haemorheological laboratory medicine in the region.