The current update considered evidence for three questions, worded in PICO format⁴ , namely:
- In people of all ages at risk of active TB, does a 4-month daily rifampicin regimen safely prevent TB disease compared to other recommended TB preventive treatment regimens? (PICO 6)
- In people of all ages at risk of active TB, does a 1-month daily rifapentine plus isoniazid regimen safely prevent TB disease compared to other recommended TB preventive treatment regimens? (PICO 7)
- In pregnant and postpartum women, is isoniazid preventive treatment for TB as safe as other preventive treatment regimens? (PICO 9)
In addition to these new questions the wording of some of the recommendations dating from before the current update, along with their accompanying conditions, was revised to improve clarity. Some recommendations in previous guidelines applied differently to high and low TB incidence countries and settings (using a threshold of 100 TB cases per 100,000 population nationally to differentiate), primarily out of concerns about variable intensity of background TB transmission, as well as programmatic capacity to rule out active TB reliably and to provide adequately for newer treatments regimens and care. In 2019, the GDG that produced the WHO consolidated guidelines on tuberculosis: tuberculosis preventive treatment decided to stress these conditions under implementation considerations instead of restricting the recommendations based upon a TB incidence threshold.
When making their decisions about the wording and strength of the recommendations the GDG members took into account not only the evidence for effectiveness and safety of an intervention but also considered other dimensions important to both patient and programme, namely values, preferences, resource requirements, cost, impact on health equity, acceptability and feasibility. This is detailed in the GRADE Evidence to Decision Tables (Annex 3).