A cost optimization approach to occupational health screening for tuberculosis

Introduction: National UK guidelines recommend a two-staged screening process for Tuberculosis (TB) in new-entrants to the National Health Service using a chest radiograph (CXR), followed by a Mantoux test and or an Interferon Gamma Release Assay (IGRA) test. The IGRA test appears to be more cost-effective, with a higher sensitivity and specificity than the Mantoux test. Trials in community settings, using first line IGRA test, then CXR, have been more cost-effective compared to the guideline approach. Budgetary constraints necessitate allocating the existing screening resources judiciously. Aim: To assess the effectiveness of first line IGRA test followed by CXR in TB screening. Methods: A retrospective study of 246 new-entrant healthcare workers with risk factors for TB, based on symptoms, IGRA tests and CXR was undertaken. Criteria for Latent Tuberculosis Infection (LTBI) were positive IGRA test and a normal CXR. Results: The prevalence of LTBI was 16.7%. CXRs were needed in 236 subjects. Only 128 (52%) had CXRs done, which did not show active TB; 87 of them had negative IGRA tests, and no documented risk factors for TB. The 108 that declined CXRs did not report any symptom of TB, and 105 of them had negative IGRA tests. Normal CXRs, within the preceding year, were associated with LTB1 (p<0.05). CXRs could have been avoided in the 192 subjects (81%) who had a negative IGRA tests had this test been done first. Conclusion: The “IGRA test first” protocol is more cost-effective than a “CXR first protocol”, during TB screening, due to a reduction in the number of CXRs required. The presence of symptoms, a positive IGRA/Mantoux test, or risk factors for active TB should be indications for a CXR.