A study in Lagos comparing TB screening methods among schoolchildren found that mobile X-ray screening with CAD was more effective than the WHO four-symptom screen, detecting more TB cases with fewer tests needed. This highlights the value of investing in mobile X-ray technology for active TB case-finding in similar populations.

  • The study compared the yield from the WHO four-symptom screen (W4SS) and mass mobile X-ray screening with CAD in similar groups of schoolchildren (ages 6 to 15) during an active case-finding activity in Lagos.
  • Presumptive TB cases were identified and sputum samples were taken to be analysed using the GeneXpert MTB/RIF. The presumptive TB cases who couldn’t produce samples or returned negative from GeneXpert had their chest X-ray films reviewed and then sent for a clinical assessment.
  • Over 6 months, a total of 13,384 schoolchildren were screened. In the W4SS group, 11,097 were administered by the W4SS checklist, 1,143 presumptive TB were identified and 70 active TB cases were found. In the X-ray with CAD group, 2,287 were screened, 129 presumptive were identified and 15 TB cases were found.
  • With W4SS, the Number Needed to Screen (NNS) was 158 and the Number Needed to Test (NNT) was 16. With CXR intervention, NNS was 152 and NNT was 9.
  • Active case-finding based on CXR was preferable as the yield was better than the W4SS. Therefore, fewer cases would be missed and it would be worthwhile to invest more in the mobile CXR.

REFERENCE: A. Alege et al. (2022, November 8-11). Comparison of yield from symptomatic W4SS screening and mass mobile X-ray in schoolchildren in Lagos, Nigeria. The Union World Conference on Lung Health 2022.