The epidemiology of chronic kidney disease and the association with non-communicable and communicable disorders in a population of sub-Saharan Africa

Abstract

In sub-Saharan Africa (SSA), epidemiological data for chronic kidney disease (CKD) are scarce. We conducted a prospective cross-sectional study including 952 patients in an outpatient clinic in Tanzania to explore CKD prevalence estimates and the association with cardiovascular and infectious disorders. According to KDIGO, we measured albumin-to-creatinine ratio and calculated eGFR using CKD-EPI formula. Factors associated with CKD were calculated by logistic regression. Venn diagrams were modelled to visualize interaction between associated factors and CKD. Overall, the estimated CKD prevalence was 13.6% (95% CI 11-16%). Ninety-eight patients (11.2%) (95% CI 9-14%) were categorized as moderate, 12 (1.4%) (95% CI 0-4%) as high, and 9 (1%) (95% CI 0-3%) as very high risk according to KDIGO. History of tuberculosis (OR 3.75, 95% CI 1.66-8.18; p = 0.001) and schistosomiasis (OR 2.49, 95% CI 1.13-5.18; p = 0.02) were associated with CKD. A trend was seen for increasing systolic blood pressure (OR 1.02 per 1 mmHg, 95% CI 1.00-1.03; p = 0.01). Increasing BMI (OR 0.92 per 1kg/m2, 95% CI 0.88-0.96; p = <0.001) and haemoglobin (OR 0.82 per 1g/dL, 95% CI 0.72-0.94; p = 0.004) were associated with risk reduction. Diabetes was associated with albuminuria (OR 2.81, 95% CI 1.26-6.00; p = 0.009). In 85% of all CKD cases at least one of the four most common factors (hypertension, diabetes, anaemia, and history of tuberculosis or schistosomiasis) was associated with CKD. A singular associated factor was found in 61%, two in 14%, and ≥3 in 10% of all CKD cases. We observed a high prevalence estimate for CKD and found that both classical cardiovascular and neglected infectious diseases might be associated with CKD in a semi-rural population of SSA. Our finding provides further evidence for the hypothesis that the "double burden" of non-communicable and endemic infectious diseases might affect kidney health in SSA.

Fig 1. Study flow.

ACR: Albumin-creatinine-ratio; eGFR: estimated glomerular filtration rate; albuminuria: ACR ≥30mg/g, (≥3 mg/mmol); impaired kidney function: eGFR <60ml/min/1.73m²; CKD: chronic kidney disease (ACR ≥30mg/g (≥3mg/mmol) and/or eGFR <60ml/min/1.73m²).

Fig 2. Distribution of patients based on eGFR and albuminuria with prevalence estimates according KDIGO chronic kidney disease risk groups [28].

Green: low CKD risk; yellow: moderate CKD risk; orange: high CKD risk; red: very-high CKD risk. ^a-f Subset of patients with evidence of systemic acute infection/inflammation or urinary tract infection (UTI) excluded from prevalence calculation (n = 54; 1/55 with acute infection/inflammation not shown due to missing ACR). ACR: albumin-creatinine-ratio; eGFR: estimated glomerular filtration rate; CKD: chronic kidney disease; KDIGO: Kidney disease improving global outcomes.

Fig 3. Venn diagram for interaction between chronic kidney disease and associated factors.

(a-d) Relationship between associated factors and chronic kidney disease (CKD). Overlapping areas: patients with CKD and a single associated factor and vice versa; (e) Interaction between the four associated factors,—elevated BP (red), diabetes (brown), anaemia (yellow) and history of schistosomiasis/tuberculosis (green) -, in relation to CKD (blue). The numbers indicate patients with CKD, one or more associated factors and overlap between CKD and associated factors. Of all CKD cases 85% (n = 101) are overlapping at least one associated factor, 15% (n = 18) are not associated to one of these factors. ^a TB: tuberculosis ^bSch: schistosomiasis; ^cElevated BP: elevated blood pressure (≥140/90 mmHg); CKD: chronic kidney disease (eGFR <60ml/min/1.73m2 or albumin-to-creatinine ratio (ACR) ≥30mg/g (≥3mg/mmol)).