Can tuberculosis and COVID-19 be tested on the same type of specimen?
The diagnostic methods for tuberculosis (TB) and COVID-19 are quite distinct and commonly require different specimens.
Sputum, as well as many other biological specimens, can be used to diagnose TB using culture or molecular techniques.
Tests for COVID-19 are done most commonly by nasopharyngeal or oropharyngeal swab or wash in ambulatory patients, but sputum or endotracheal aspirate or bronchoalveolar lavage may be used in patients with severe respiratory disease. Molecular testing is the currently recommended method for the identification of infectious COVID-19 and just as for TB, serological assays are not recommended for the routine diagnosis of COVID-19.
The pipeline for COVID-19 diagnostics has flourished impressively within a few months. Amongst these is the Xpert® Xpress SARS-CoV-2 cartridge for use on GeneXpert machines, which are machines used in TB diagnosis. WHO is currently evaluating this cartridge as well as other tests. Additional resources to roll out COVID-19 testing should be mobilized rather than relying only on existing resources that are used for TB, to ensure that the diagnostic coverage for TB is maintained as necessary.