CD4 and tuberculosis: RISK11 positive predictive values for primary endpoint prevalent (2·5%) and incident disease (3·2%) were computed with the observed tuberculosis prevalence (1%) and incidence rates (0·9% annually), which, in this ambulatory community setting, were lower than that typically used in estimations (2%).16, 17, 36 Whether these results are generalisable to other geographical or clinical settings, such as people with HIV seeking health care or who are hospitalised with advanced HIV and low CD4 cell counts, remains to be seen.