HAEMATOLOGICAL PROFILE OF CHRONIC KIDNEY DISEASE IN A MIXED-ANCESTRY SOUTH AFRICAN POPULATION

Abstract

Objective: Chronic kidney disease (CKD) encompasses a range of physiological processes altered by the progressive decline in glomerular filtration rate (GFR). Haematological factors, particularly red blood cell (RBC) indices, are most commonly affected, giving rise to anaemia. This study aimed to characterise the haematological profile of screen-detected CKD patients in a community-based sample, and to correlate the blood count measures with the commonly advocated kidney function estimators of CKD in urban South Africans. Design and method: Mixed-ancestry adults (n = 1564) were examined between February and November 2015. Kidney function was assessed using serum creatinine-based estimators of GFR (eGFR), including the Modification of Diet in Renal Disease (MDRD) and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations; omitting the ethnicity correction factor. CKD was defined as an eGFR < 60 ml/min/1.73m2, anaemia as a haemoglobin level < 13.5 g/dL (men) and < 12 g/dL (women) and hypertension as a systolic blood pressure (BP) > 140mmHg and/or diastolic BP > 90 mmHg. Results: Based on the MDRD and CKD-EPI equations, the crude prevalence of CKD was 6% and 3%, with 53.2% and 63.3% of these individuals being hypertensive. Irrespective of the eGFR equation used, RBC indices were consistently lower in CKD patients compared to those with normal kidney function [RBC count (MDRD): median (25th–75th percentiles): 4.3(3.9–4.7) vs. 4.7(4.4–5.0) ×10^6cells/μl, p < 0.0001; (CKD-EPI): 4.2(3.8–4.7) vs. 4.7(4.4–5.0) x10^6cells/μl, p < 0.0001, haematocrit (MDRD): median (25th–75th percentiles): 38(35–41) vs. 41(39–44)%, p < 0.0001; (CKD-EPI): 37(34–41) vs. 41(39–44)%, p < 0.0001 and haemoglobin (MDRD): median (25th–75th percentiles): 12.2(11.2–13.3) vs. 13.5(12.7–14.5) g/dL, p < 0.0001; (CKD-EPI): 11.9(11.1–13.2) vs. 13.5(12.6–14.4) g/dL, p < 0.0001]. Of the CKD patients, 45.5% (MDRD) and 57.8% (CKD-EPI) were anaemic, with the prevalence increasing with increasing severity of CKD, from 17.2% (stage 1) to 82.4% (stages 4–5). Furthermore, CKD-EPI-eGFR, but not MDRD-eGFR, was positively associated with RBC indices and anaemia. Conclusions: Though it remains unclear whether the advocated kidney function estimators provide accurate estimates of CKD burden in Africans, the correlation of their estimates with deteriorating profile of RBC (an indicator of the severity of kidney function impairment), suggests that advocated GFR estimates, to some extent measure the true kidney function in African populations.