Chronic respiratory disease observatory for Africa (CHEST-Africa): study protocol for the prevalence, determinants and economic impacts of asthma and COPD in Africa

Introduction: Contemporary data on the burden of chronic respiratory diseases in sub-Saharan Africa is limited. More so, their economic burden is not well described. This study aims to establish a chronic respiratory disease observatory for Africa. Specific study aims are (1) to describe the prevalence and determinants of asthma with a target to screen up to 4000 children and adolescents across four African cities; (2) to determine the prevalence and determinants of chronic obstructive pulmonary disease (COPD) with a target to screen up to 3000 adults (≥18 years) across five African cities; (3) to describe the disease burden by assessing the frequency and severity of symptoms and exacerbations, medication use, emergency healthcare utilisation and hospitalisation; and (4) to assess the economic burden and affordability of the medicines for these diseases. Methods and analysis: Surveys will be conducted in schools to identify children and adolescents with asthma using the Global Asthma Network screening questionnaire in Ghana, Nigeria, the Democratic Republic of Congo, and Uganda. Community surveys will be conducted among adults using an adapted version of the Burden of Obstructive Lung Disease Questionnaire to identify persons with COPD symptoms in Nigeria, Burkina Faso, Mozambique, Rwanda, and Sierra Leone. Fractional exhaled nitric oxide and pre-bronchodilator and post-bronchodilator spirometry will be done for children with asthma or asthma symptoms and for all adult participants. Children and adults with respiratory symptoms or diagnoses will complete the health economic questionnaires. Statistical analysis will involve descriptive and analytical statistics to determine outcomes. Ethics and dissemination: Ethical approval has been obtained from participating institutions. This study’s results will inform deliberations at the United Nations General Assembly high-level meeting on non-communicable diseases in 2025. The results will be shared through academic conferences and journals and communicated to the schools and the communities

Predicting the environmental suitability and population at risk of podoconiosis in Africa

Podoconiosis is a type of tropical lymphedema that causes massive swelling of the lower limbs. The disease is associated with both economic insecurity, due to long-term morbidity-related loss of productivity, and intense social stigma. The geographical distribution and burden of podoconiosis in Africa are uncertain. We applied statistical modelling to the most comprehensive database compiled to date to predict the environmental suitability of podoconiosis in the African continent. By combining climate and environmental data and overlaying population figures, we predicted the environmental suitability and human population at risk of podoconiosis in Africa. Environmental suitability for podoconiosis was predicted in 29 African countries. In the year 2020, the total population in areas suitable for podoconiosis is estimated at 114.5 million people, (95% uncertainty interval: 109.4–123.9) with 16.9 million in areas suitable for both lymphatic filariasis and podoconiosis. Of the total 5,712 implementation units (typically second administrative-level units, such as districts) defined by the World Health Organization in Africa, 1,655 (29.0%) were found to be environmentally suitable for podoconiosis. The majority of implementation units with high environmental suitability are located in Angola (80, 4.8%), Cameroon (170, 10.3%), the DRC (244, 14.7%), Ethiopia (495, 29.9%), Kenya (217, 13.1%), Uganda (116, 7.0%) and Tanzania (112, 6.8%). Of the 1,655 environmentally suitable implementation units, 960 (58.0%) require more detailed community-level mapping. Our estimates provide key evidence of the population at risk and geographical extent of podoconiosis in Africa, which will help decision-makers to better plan more integrated intervention programmes

Translating preventive chemotherapy prevalence thresholds for Schistosoma mansoni from the Kato-Katz technique into the point-of-care circulating cathodic antigen diagnostic test.

BACKGROUND:Intervention guidelines against Schistosoma mansoni are based on the Kato-Katz technique. However, Kato-Katz thick smears show low sensitivity, especially for light-intensity infections. The point-of-care circulating cathodic antigen (POC-CCA) is a promising rapid diagnostic test detecting antigen output of living worms in urine and results are reported as trace, 1+, 2+, and 3+. The use of POC-CCA for schistosomiasis mapping, control, and surveillance requires translation of the Kato-Katz prevalence thresholds into POC-CCA relative treatment cut-offs. Furthermore, the infection status of egg-negative but antigen-positive individuals and the intensity-dependent sensitivity of POC-CCA should be estimated to determine its suitability for verification of disease elimination efforts. METHODOLOGY:We used data from settings in Africa and the Americas characterized by a wide range of S. mansoni endemicity. We estimated infection intensity-dependent sensitivity and specificity of each test at the unit of the individual, using a hierarchical Bayesian egg-count model that removes the need to define a 'gold' standard applied to data with multiple Kato-Katz thick smears and POC-CCA urine cassette tests. A simulation study was carried out based on the model estimates to assess the relation of the two diagnostic tests for different endemicity scenarios. PRINCIPAL FINDINGS:POC-CCA showed high specificity (> 95%), and high sensitivity (> 95%) for moderate and heavy infection intensities, and moderate sensitivity (> 75%) for light infection intensities, and even for egg-negative but antigen-positive infections. A 10% duplicate slide Kato-Katz thick smear prevalence corresponded to a 15-40% prevalence of ≥ trace-positive POC-CCA, and 10-20% prevalence of ≥ 1+ POC-CCA. The prevalence of ≥ 2+ POC-CCA corresponded directly to single slide Kato-Katz prevalence for all prevalence levels. CONCLUSIONS/SIGNIFICANCE:The moderate sensitivity of POC-CCA, even for very light S. mansoni infections where the sensitivity of Kato-Katz is very low, and the identified relationship between Kato-Katz and POC-CCA prevalence thresholds render the latter diagnostic tool useful for surveillance and initial estimation of elimination of S. mansoni. For prevalence below 10% based on a duplicate slide Kato-Katz thick smear, we suggest using POC-CCA including trace results to evaluate treatment needs and propose new intervention thresholds that need to be validated in different settings