Rapid point of care tests in Zimbabwe: immunological and sociological perspectives

Rapid point-of-care (POC) tests overcome many of the limitations imposed by traditional diagnostics, with respect to turnaround time, expenses and laboratory infrastructure. This is particularly beneficial in resource-limiting environments, such as rural Zimbabwe, where this study analysed the use of POC tests from immunological and sociological perspectives. Preliminary work was carried out to establish proof-of-concept for rapid TB diagnostics, in a Schistosoma haematobium-endemic region. This project aimed to quantify the levels of specific immunoglobulin M (IgM) and immunoglobulin G (IgG) against five unique Mycobacterium tuberculosis peptides, thereby understanding the patterns of humoral immunity between differing sex and age groups, and the effects of schistosome infection. The number of S. haematobium eggs were counted in stool and enzyme-linked immunoabsorbent assays (ELISAs) were performed on sera to quantify peptide-specific antibody levels. The results were then stratified by sex and schistosomiasis status of participants, prior to analysis of antibody titres with age. M. tuberculosis sensitisation was prevalent throughout the cohort and various sex-, age- and schistosomiasis-associated differences were identified. Peak female IgM titres were experienced higher and at a younger age with respect to males. As for IgG titres, females displayed a biphasic spectrum, seeing antibody levels peak twice in adulthood. By contrast, males experienced one peak IgG titre in middle age. Schistosomiasis disease status was associated with peak titre expression in younger age groups and elevated IgG levels; however, it exerted inconsistent effects on the magnitude of IgM responses. This demonstrated how serodiagnostics can be used to quantify bacterial exposure and characterise the immunomodulatory effects of parasite infection. Additionally, attitudes towards the use of POC tests were investigated. This aimed to establish whether participants were willing and able to self-diagnose COVID-19 using lateral flow tests (LFTs), as well as to ascertain whether they were cognizant of undertaking self-isolation when appropriate. Village health workers (VHWs) counselled participants on the correct usage of LFTs, which they then completed independently. A questionnaire was then conducted to capture information on the demographics of the cohort, COVID-19-associated behaviours and testing preferences. Descriptive statistics for the responses were reported and demographic factors associated with willingness to test identified. Most participants (90.8%) were willing to use LFTs and primarily reported preferences for self-testing as it was easier, pain-free, convenient and confidential. Farmers and followers of the Apostolic faith were found to be overrepresented among those unwilling to test, indicating that these individuals would be less likely to respond to LFT distribution. Participants displayed high levels of health literacy, demonstrated by questionnaire responses to COVID-19 transmission-mitigating and sanitary behaviours. Taken together, immunological and sociological analysis inform context specific POC diagnostics, which is essential for implementation of novel health interventions.