Underdiagnosis of hypertension and diabetes mellitus in South Africa

Background. Hypertension and diabetes mellitus (DM) are major causes of natural death in South Africa (SA). Underdiagnosis of these treatable diseases would hamper efforts to improve their management and hence reduce morbidity and mortality. Objectives. To assess the level of underdiagnosis of hypertension and DM in SA. Methods. Data from adult participants (≥15 years) in the 2016 South African Demographic and Health Survey, which draws a nationally representative sample of the population, was used. Using these data, the prevalence of hypertension and DM was assessed at the time of the study using objective criteria (hypertension: systolic blood pressure ≥140 mmHg and/or diastolic blood pressure ≥90 mmHg; DM: glycated haemoglobin (HbA1c) ≥6.5%), and disease prevalence based on participant recall of having ever received a diagnosis of hypertension or DM from a healthcare professional. The difference between the objectively measured prevalence of the diseases and the prevalence based on recall was used to assess the level of underdiagnosis. Results. Of 10 336 adult participants who answered the question on the recall of a diagnosis, 8 092 had their blood pressure measured, and 6 740 had HbA1c assessed. The prevalence of hypertension based on recall was 18.9% (95% confidence interval (CI) 17.7 - 20.1), while the prevalence using blood pressure measurements was 37.1% (95% CI 35.3 - 38.9). Therefore, 49% of cases of hypertension are likely to be undiagnosed (~7.1 million people). The prevalence of DM based on recall was 4.5% (95% CI 3.9 - 5.1), and 11.4% (95% CI 10.4 - 12.4) based on HbA1c values. Therefore, 61% of cases of DM are likely to be undiagnosed (~2.7 million people). Conclusions. There is significant underdiagnosis of hypertension and DM in SA. The underdiagnosis of these two treatable conditions, which have high morbidity and mortality, has major population health implications.