International Blood Research & Reviews

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

Adenuga Jacob Olaitan — 2026-05-14

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.

Thrombo-Haemorheological Coupling in Haemoglobinopathies: Mechanistic Insights into the Bidirectional Interplay between Coagulation Activation and Erythrocyte Flow Properties

Adenuga Jacob Olaitan — 2026-05-16

Hemoglobinopathies (e.g., HbS, HbC, HbF) are the most common single-gene disorders worldwide, especially in sub-Saharan Africa. Beyond affecting red blood cells and oxygen transport, they significantly disrupt blood clotting (hemostasis) and blood flow properties (haemorheology).

This review synthesizes current evidence from molecular biology, cellular hematology, and clinical hemostasis research to construct a mechanistically integrated framework for thrombo-haemorheological coupling in hemoglobinopathies. We examine how hemoglobin structural variants alter erythrocyte membrane phospholipid topology, intracellular viscosity, and cytoskeletal integrity to produce downstream procoagulant signaling, and conversely, how activated coagulation factors, fibrin deposition, and platelet-mediated networks feed back to impair erythrocyte flow properties. Specific genotype-phenotype relationships are examined across HbAA, HbAS, HbSS, HbSC, HbCC, HbAC, and elevated HbF phenotypes. The role of the vascular endothelium, neutrophil extracellular traps (NETs), and the thrombo-inflammatory axis is critically evaluated. We propose the Thrombo-Haemorheological Coupling Axis (THCA) as a framework for future research and therapeutic targeting.

RhD Frequency and Maternal Alloimmunisation Among Pregnant Women Attending Federal Medical Centre, Asaba, Nigeria: Implications for Preventing Foetal and Newborn Haemolytic Disease

Kevin Erhamwonyia Aghatise — 2026-05-13

Background: Maternal alloimmunisation against the RhD antigen remains a preventable cause of haemolytic disease of the foetus and newborn (HDFN), a condition responsible for substantial perinatal morbidity and mortality in resource-limited settings. Population-specific data on RhD phenotype frequency and alloimmunisation burden are critical to designing appropriate antenatal prophylaxis programmes in sub-Saharan Africa.

Objectives: To determine the frequency of the RhD-negative phenotype and the prevalence of maternal alloimmunisation among pregnant women attending a tertiary antenatal clinic in Asaba, Delta State, south-south Nigeria, and to examine the age and parity distribution of RhD-negative women.

Methods: A prospective, observational, cross-sectional study was conducted among 200 pregnant women of varying gravidity attending the antenatal clinic of Federal Medical Centre Asaba. RhD phenotyping was performed using standard tube agglutination with polyclonal anti-D antisera. Indirect antiglobulin test (IAT) was performed on the sera of all RhD-negative women using pooled group O red cells and antihuman globulin to screen for clinically significant alloantibodies. Ethical approval was obtained from the hospital's Health Research and Ethics Committee.

Results: RhD-positive phenotype was identified in 192/200 (96.0%) and RhD-negative in 8/200 (4.0%) participants. The majority of participants were in the 31–35-year age group (37.0%) and were primigravid (48.0%). Among the 8 RhD-negative women, 1 (12.5%) was alloimmunised, corresponding to an overall alloimmunisation rate of 0.5% of the total cohort. No alloantibodies were detected in RhD-positive women.

Conclusions: The RhD-negative frequency of 4.0% is consistent with reported values for south-south Nigeria and broader sub-Saharan African populations. An alloimmunisation rate of 12.5% among RhD-negative women signals a clinically meaningful burden that warrants universal antenatal antibody screening, structured anti-D immunoprophylaxis, and systematic screening of all RhD-negative women regardless of parity.

Pancytopenia in Narcotic Addicts: A 3-Year Study in a South-South Nigerian Tertiary Hospital (Ages 21–35)

Ndudi Dibigbo–Ibeaji — 2026-05-14

Background: Pancytopenia reflects a failure of normal hematopoiesis or excessive destruction or sequestration of blood cells and is frequently associated with significant morbidity and mortality if not promptly identified and managed. Despite growing global recognition of the systemic complications associated with substance use disorders, there remains a substantial gap in the understanding of the relationship between narcotic addiction and pancytopenia, particularly in low- and middle-income regions such as Sub-Saharan Africa.

Aim: This study aimed to evaluate the haematological profile of young adult narcotic addicts aged 21-35 years and determine the occurrence of pancytopenia among this population in a tertiary healthcare setting in South-South Nigeria.

Study design: This was a hospital-based retrospective descriptive study.

Place and Duration of Study: The study was conducted in a tertiary healthcare institution in South-South Nigeria over a three-year period.

Methodology: A total of 22 young adult patients aged 21–35 years with documented history of narcotic addiction who had undergone full blood count investigations during the study period were included. Relevant demographic and laboratory data including age, gender, packed cell volume (PCV), total white blood cell (WBC) count, and platelet count were extracted from laboratory records using a structured data extraction format. Haematological parameters were analyzed using a Mindray BC-5000 5-part differential automated haematology analyzer. Data were analyzed using Statistical Package for Social Sciences (SPSS) version 27. Descriptive statistics were presented as mean ± standard deviation, minimum and maximum values. Comparison of haematological parameters across age groups (<30 years and ≥30 years) and gender (male and female) was performed using the Mann-Whitney U test. Statistical significance was set at P < 0.05.

Results: The mean age of participants was 28.09 ± 3.7 years. The mean packed cell volume was 23.86 ± 6.81%, mean total white blood cell count was 2890.90 ± 3437.49 cells/µL, and mean platelet count was 43,759.09 ± 30,922.78 cells/µL, indicating reductions across all three haematopoietic cell lines consistent with pancytopenia. Comparison across age groups showed no statistically significant differences in PCV (P = 0.688), WBC (P = 0.591), or platelet count (P = 0.640). Similarly, gender-based comparisons revealed no statistically significant differences in PCV (P = 0.457), WBC (P = 0.566), or platelet count (P = 0.110).

Conclusion: This study demonstrated the presence of pancytopenia among young adult narcotic addicts in a hospital-based population in South-South Nigeria. In the absence of HIV and viral hepatitis coinfection among participants, the observed haematological abnormalities are more likely attributable to opioid-related immune modulation, nutritional deficiencies, and possible exposure to toxic adulterants associated with illicit drug use. Routine haematological evaluation should therefore form an essential component of clinical assessment in individuals with narcotic addiction.

Correlates of Systolic Blood Pressure Among Middle-Aged U.S. Adults: A Survey-weighted Regression Analysis of NHANES Data (2017 – 2018)

Gideon Kwame Gargar — 2026-05-14

Background: Hypertension is a leading modifiable risk factor for cardiovascular disease, and midlife is a critical period when adverse systolic blood pressure (SBP) trajectories emerge. We estimated nationally representative associations between SBP and demographic, socioeconomic, behavioral, and anthropometric factors among U.S. adults aged 40 - 64 years.

Methodology: We analysed the National Health and Nutrition Examination Survey (NHANES) (2017–2018) Mobile Examination Center (MEC) data (N=1,884 adults). SBP was defined as the mean of up to four standardized systolic readings. Age, body mass index (BMI), and income-to-poverty ratio (PIR) were treated as continuous predictors. Gender, race/ethnicity, smoking status, and doctor-advised physical activity were modelled as categorical covariates. We compared main-effects and interaction models using the Bayesian Information Criterion. The main-effects model was selected and estimated using survey-weighted linear regression with MEC examination weights, strata, and primary sampling units to obtain population-level estimates.

Results: SBP increased with age (0.56 mmHg per year; 95% CI: 0.34, 0.78; p = 0.004) and BMI (0.47 mmHg per kg/m²; 95% CI: 0.23, 0.71; p = 0.008). Compared with non-Hispanic White adults, SBP was 9.01 mmHg higher among non-Hispanic Black adults (95% CI: 6.09, 11.93; p = 0.002) and 4.56 mmHg higher among non-Hispanic Asian adults (95% CI: 0.40, 8.72; p = 0.040). PIR showed an inverse but non-significant association (−0.75 mmHg; 95% CI: −1.74, 0.25; p = 0.096). Gender differences, Smoking status and doctor-advised physical activity were not statistically significant.

Conclusions: Among middle-aged U.S. adults, SBP was associated with age and adiposity. Racial and ethnic differences persisted, with SBP about 9 mmHg higher among non-Hispanic Black adults and 5 mmHg higher among non-Hispanic Asian adults compared with non-Hispanic White adults. These findings emphasise the need for midlife weight management and equity-focused hypertension prevention strategies.