Abstract
Research studies have shown that populations may have significantly different haematological parameters due to race/ethnicity or geographic location. South Africa has a notably diverse population pool within a varied geographic setting. Much research still needs to be done on the haematological diversity of the ethnic population groups within South Africa.
The study aimed to report on the data regarding parameters of the full blood count (FBC) for first-time donors, establishes distribution amongst and comparison between different ethnic groups in the South African population, and compare this to countries in the rest of Africa and globally. It was expected that there might be haematological differences in some provinces due to age, gender, race/ethnicity, and geographic location. The current gap in knowledge regarding the distribution and possible association between the full blood count parameters was investigated in association with the South African National Blood Service (SANBS). Although it is not the aim of this study, the findings could be used to determine local reference ranges, assist the SANBS in distributing their blood products more effectively and also improve disease diagnosis and management.
The study population from which the data was collected consisted of first-time blood donors, who were considered healthy at the time of blood donation, from two periods (2014 and 2019), for whom all study parameters were available. The data set for 2014 comprised of blood samples collected from all the provinces except for the Western Cape, the 2019 data set was from a larger sample size, but only included donors from the Kwa-Zulu Natal (KZN) province.
The participants were screened before the donation at the SANBS for any abnormality, including point-of-care haemoglobin testing, blood pressure testing, human immunodeficiency virus (HIV), hepatitis B and C, and syphilis testing. Repeat donors were not considered for this study, as it has been proven that continued blood donation might result in alterations in haemoglobin (Hb), haematocrit (HCT), and iron profiles in participants over time. As part of the exclusion criteria, any participants suggestive of anaemia were identified and excluded.
The data for this retrospective descriptive study was extracted from the Laboratory Information Management System (LIMS)of the SANBS, transferred to a Microsoft Excel spreadsheet, and
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analysed using IBM Statistical Package for Social Sciences (SPSS) software program. version 28.0.1.0. The data was cleaned, and outliers were removed. The frequencies were analysed for demographics, and summary statistics were done for the parameters.
The data was analysed to determine normality using the Kolmogorov-Smirnov test. Since most parameters were not normally distributed, the non-parametric test the Kruskal-Wallis test was used. After doing Mann-Whitney and Kruskal-Wallis tests, descriptive and cross-comparison tables, were used to obtain the significance of the haematological variances in the South African population regarding gender, stratified age, race/ethnicity, and geographic location (Province). Reference Intervals were established in accordance with the International Federation of Clinical Chemistry (IFCC) in the Clinical Laboratory Standards Institute (CLSI) C278-P3 guidelines. The statistical results were also compared with similar findings of countries in Africa and globally.
The study included a total of 2417 first-time donors, with 369 participants from 2014 and 2048 participants from 2019. Female donors constituted 77.9% of first-time donors, while male donors made up 22.1%. The most common age group was between 20-29 years, while the least common was between 50-59 years. Gauteng province contributed the most first-time donors (47%), with Northern Cape having the least first-time donors (1.7%). Gender-based differences were found in most of the FBC parameters, including platelets (PLT), Hb, HCT, red blood cell count (RBC), mean corpuscular haemoglobin (MCH), and mean corpuscular haemoglobin concentration (MCHC). There were no significant differences for mean corpuscular volume (MCV) in both data sets. When comparing the ethnic groups, statistically significant differences were found for most haematological parameters between the ethnic groups including ‘Black and Coloured’, ‘Black and White’, ‘Black and Asian’, and ‘White and Asian’ ethnic groups. Using the 2014 data set, significant differences were found between certain provinces. The significant provincial pairs included, ‘Eastern Cape and Gauteng’ (Hb & HCT), ‘Gauteng and Kwa-Zulu Natal (KZN)’ (MCH, Hb, RBC, HCT & MCHC), ‘Gauteng and Mpumalanga’ (RBC & HCT), ‘Free State and KZN’ (MCH), ‘KZN and Limpopo’ (MCH, MCHC, and PLT), and ‘KZN and Mpumalanga’ (MCHC). The reference intervals (RIs) provided in this study differed from the current RIs used by National Health Laboratory Services (NHLS) and SANBS.
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The study provided the distribution of the haematological parameters according to age, gender, race/ethnicity, and province for both data sets. Population-specific RIs are necessary and vital to clinical decision-making. These can help the SANBS to correctly diagnose anaemia, among other haematological abnormalities, and help increase the donor pool through improved assessment of the Hb donor deferral values. This will optimise blood product collection and distribution across the country.