Health needs are diverse, and programmes are expected to provide a range of diagnostics to assist health workers in managing patients. The diagnosis of TB often begins with symptom screening, which is not specific to TB, given that cough and fever overlap with COVID-19 and other respiratory infections. Additionally, TB patients may be coinfected with HIV, particularly in sub-Saharan Africa, and services for both diseases are usually provided at the same levels of care. The relative diagnostic volumes are also quite heterogeneous and can be low when considered by disease and by day at peripheral health centres, justifying the need for multi-disease testing using the same equipment.
All currently recommended molecular diagnostics for the initial diagnosis of TB have a SARS-CoV-2 test available on the same platform as the TB test, although not all may have received regulatory approval for such use. Several of the platforms are widely used in the diagnosis and management of PLHIV whereas others are used for antimicrobial resistance detection of bacterial pathogens. The decision to choose a particular test and brand would also need to consider the instruments available in a particular setting and the available capacity to add TB testing. If multi-disease testing on an instrument is planned, then platforms that use random access approaches (e.g. GeneXpert) or allow different types of tests to be performed on the same batch (e.g. cobas and BD Max) would be preferable.
Multi-disease testing has the advantage of shared financial costs for equipment purchasing and maintenance, as well as human resources. Efficiencies could also be achieved because such testing could result in optimal use of equipment and batch sizes. However, if not planned well, such testing could have the opposite effect. Equitable access and shared prioritization of testing are important to ensure that a group of patients with a particular disease are not disadvantaged. The overall laboratory budgets should ensure fair distribution based on burden of disease and need.
Multi-disease testing is mainly useful where the numbers of tests by individual programmes are small within a particular setting. In contrast, scenarios where there are large TB and HIV testing needs and infrastructure is installed to meet the demand, multi-disease testing will be less relevant. Nonetheless, the burden of disease and testing volumes change over time; hence, the use of equipment should be monitored and programmes may need to adapt.