Full blood count and white cell differential count reference ranges obtained from a healthy urban South African population residing in the Western Cape of South Africa

Background: Research has suggested that individuals of African descent have lower white cell and neutrophil counts than Caucasians. These differences could lead to incorrect clinical decisions, and therefore, ethnic-specific reference ranges are required. The Western Cape region of South Africa is uniquely diverse, comprising Caucasian, Mixed Ancestry and those of African descent. The aim of this study was to compare the full blood count and differential counts across the three major ethnic groups residing in this area and to propose appropriate RIs.

Methods: The study formed part of the international project led by the Committee on Reference Intervals and Decision Limits (C-RIDL), and therefore, the strict guidelines laid out by the committee were followed. Full blood count and differential counts were performed on a Beckman Coulter ACT 5 diff AL analyser within 2-4 hours of collection and were reported as mean (standard deviation), 2.5th and 97.5th percentiles. Comparisons were analysed using Spss v25 and Statistica v13, and a P value of < 0.05 was considered significant.

Results: Reference ranges for Caucasian and Mixed Ancestry individuals were similar while white cell (P = 0.016), monocyte (P < 0.001), neutrophil (P = 0.034) and red cell indices were significantly different amongst the three population groups. There were however no statistical and clinical significant differences between the eosinophil, lymphocyte, red cell and platelet counts across the three groups.

Conclusion: In conclusion, subjects of Mixed Ancestry, in this region, have similar reference intervals to those of European descent, while lower white cell and neutrophil counts in Africans have been confirmed.