Forgotten but not gone in rural South Africa: Urinary schistosomiasis and implications for chronic kidney disease screening in endemic countries

Background: Urinary schistosomiasis caused by infection with Schistosoma haematobium (S. haematobium) remains endemic in Africa and is associated with haematuria and albuminuria/proteinuria. Kidney Disease Improving Global Outcomes clinical guidelines recommend evaluating proteinuria/albuminuria and glomerular filtration rate for chronic kidney disease (CKD) diagnosis. The guidelines are informed by population data outside of Africa but have been adopted in many African countries with little validation. Our study aimed to characterise the burden of urinary schistosomiasis in rural South Africa (SA) and evaluate its relationship with markers of kidney dysfunction with implications for CKD screening. Methods: In this population-based cohort study, we recruited 2021 adults aged 20 – 79 years in the Mpumalanga Province, SA. Sociodemographic data were recorded, urinalysis performed, and serum creatinine and urine albumin and creatinine measured. Kidney dysfunction was defined as an estimated glomerular filtration rate (eGFR) 3.0mg/mmol. S. haematobium infection was determined by urine microscopy. Multivariable analyses were performed to determine relationships between S. haematobium and markers of kidney dysfunction. Results: Data were available for 1226 of 2021 participants. 717 (58.5%) were female and the median age was 35 years (IQR 27 – 47). Prevalence of kidney dysfunction and S. haematobium was 20.2% and 5.1% respectively. S. haematobium was strongly associated with kidney dysfunction (OR 8.66; 95% CI 4.10 – 18.3) and related to albuminuria alone (OR 8.69; 95% CI 4.11 – 18.8), with no evidence of an association with eGFR <90ml/min/1.73m2 (OR 0.43; 95% CI 0.05 – 3.59). Discussion: The strong association between urinary schistosomiasis and albuminuria requires careful consideration when screening for CKD. Screening for, and treatment of, schistosomiasis should be a routine part of initial work-up for CKD in S. haematobium endemic areas. Urinary schistosomiasis, a neglected tropical disease, remains a public health concern in the Mpumulanga province of SA

Chronic kidney disease (CKD) and associated risk in rural South Africa: a population-based cohort study.

BACKGROUND: In Africa, true prevalence of chronic kidney disease (CKD) is unknown, and associated clinical and genetic risk factors remain understudied. This population-based cohort study aimed to investigate CKD prevalence and associated risk factors in rural South Africa. METHODS: A total 2021 adults aged 20-79 years were recruited between 2017-2018 from the Agincourt Health and Socio-Demographic Surveillance System in Bushbuckridge, Mpumalanga, South Africa. The following were collected: sociodemographic, anthropometric, and clinical data; venous blood samples for creatinine, hepatitis B serology; DNA extraction; spot urine samples for dipstick testing and urine albumin: creatinine ratio (UACR) measurement. Point-of-care screening determined prevalent HIV infection, diabetes, and hypercholesterolemia. DNA was used to test for apolipoprotein L1 (APOL1) kidney risk variants. Kidney Disease Improving Global Outcomes (KDIGO) criteria were used to diagnose CKD as low eGFR (<60mL/min/1.73m2) and /or albuminuria (UACR ≥ 3.0mg/mmol) confirmed with follow up screening after at least three months. eGFR was calculated using the CKD-EPI(creatinine) equation 2009 with no ethnicity adjustment. Multivariable logistic regression was used to model CKD risk. RESULTS: The WHO age-adjusted population prevalence of CKD was 6.7% (95% CI 5.4 - 7.9), mostly from persistent albuminuria. In the fully adjusted model, APOL1 high-risk genotypes (OR 2.1; 95% CI 1.3 - 3.4); HIV infection (OR 1.8; 1.1 - 2.8); hypertension (OR 2.8; 95% CI 1.8 - 4.3), and diabetes (OR 4.1; 95% CI 2.0 - 8.4) were risk factors. There was no association with age, sex, level of education, obesity, hypercholesterolemia, or hepatitis B infection. Sensitivity analyses showed that CKD risk factor associations were driven by persistent albuminuria, and not low eGFR. One third of those with CKD did not have any of these risk factors. CONCLUSIONS: In rural South Africa, CKD is prevalent, dominated by persistent albuminuria, and associated with APOL1 high-risk genotypes, hypertension, diabetes, and HIV infection

Chronic kidney disease (CKD) and associated risk in rural South Africa: a population-based cohort study.

Background: In Africa, true prevalence of chronic kidney disease (CKD) is unknown, and associated clinical and genetic risk factors remain understudied. This population-based cohort study aimed to investigate CKD prevalence and associated risk factors in rural South Africa. Methods: A total 2021 adults aged 20-79 years were recruited between 2017-2018 from the Agincourt Health and Socio-Demographic Surveillance System in Bushbuckridge, Mpumalanga, South Africa. The following were collected: sociodemographic, anthropometric, and clinical data; venous blood samples for creatinine, hepatitis B serology; DNA extraction; spot urine samples for dipstick testing and urine albumin: creatinine ratio (UACR) measurement. Point-of-care screening determined prevalent HIV infection, diabetes, and hypercholesterolemia. DNA was used to test for apolipoprotein L1 (APOL1) kidney risk variants. Kidney Disease Improving Global Outcomes (KDIGO) criteria were used to diagnose CKD as low eGFR (<60mL/min/1.73m2) and /or albuminuria (UACR ≥ 3.0mg/mmol) confirmed with follow up screening after at least three months. eGFR was calculated using the CKD-EPI(creatinine) equation 2009 with no ethnicity adjustment. Multivariable logistic regression was used to model CKD risk. Results: The WHO age-adjusted population prevalence of CKD was 6.7% (95% CI 5.4 - 7.9), mostly from persistent albuminuria. In the fully adjusted model, APOL1 high-risk genotypes (OR 2.1; 95% CI 1.3 - 3.4); HIV infection (OR 1.8; 1.1 - 2.8); hypertension (OR 2.8; 95% CI 1.8 - 4.3), and diabetes (OR 4.1; 95% CI 2.0 - 8.4) were risk factors. There was no association with age, sex, level of education, obesity, hypercholesterolemia, or hepatitis B infection. Sensitivity analyses showed that CKD risk factor associations were driven by persistent albuminuria, and not low eGFR. One third of those with CKD did not have any of these risk factors. Conclusions: In rural South Africa, CKD is prevalent, dominated by persistent albuminuria, and associated with APOL1 high-risk genotypes, hypertension, diabetes, and HIV infection

Dataset From: Forgotten but not gone in rural South Africa: Urinary schistosomiasis and implications for chronic kidney disease screening in endemic countries

Supporting dataset showing sociodemographic data from this population-based cohort study