Usefulness of PPD in the screening of TB in a cohort of HIV infected children and young adults in Uganda

Background: Concern is imminent, 2/3 of the world population is infected with TB, and HIV infection is on the rise especially in Sub-Saharan Africa. Co-infection is lethal because HIV increases the risk of TB infection through reactivation of latent TB, rapid progression to an already existing TB disease, re-infection and relapse, and TB IRIS for patients initiated on HAART. Screening test for early diagnosis and treatment is needed for the reduction of morbidity and mortality associated with TB. Methods: Medical records of HIV infected children and young adults who attended a pediatric clinic in Kampala, Uganda from 2003 to 2009. The outcome was defined as TB in the first six months after registration and PPD was the main predictor. PPD was given to patients who were not on TB treatment at the time of registration to know whether they were exposed to M. bacterium. TB status was considered after six months from registration to ensure that, at that time, all investigations had been concluded, and the TB status of the child known. TB diagnosis was done on the basis of sputum, lympnode biopsy and chest X-ray. Results: PPD test was found to be 43.5% (95% CI: 39.5, 47.3), specificity was 94.8% (95%CI: 93.5, 95.8). Area under the curve was 0.6 (95%CI: 0.67, 0.71) Conclusion: PPD test had a poor sensitivity but very good specificity