Utilizing chest X-ray based active case finding approach for early tuberculosis case detection in Pakistan

Introduction: Pakistan has the third largest number of people with undiagnosed TB among the 22 high TB-burden countries. Case detection gap results in late disease presentation, with poor disease outcomes, and undiagnosed cases spreading infection. To bridge this gap, active case finding (ACF) using pre-screening tools such as chest X-ray can be used to detect TB early in the course of illness while MTB burden is still low. Methodology: Retrospective data from Xpert MTB/RIF testing carried out at TB centers, called “Sehatmand Zindagi” centers, in Pakistan, from January to December 2018 was analyzed. The referrals for Xpert testing came from 3 distinct sources; 1) GP referral for TB investigation of presumptive TB patients, 2) ACF program using CAD4TB supported digital chest X-rays in mobile vans, whereby a CAD4TB cut-off of greater than 70 was tested on Xpert, 3) self-referred for TB investigation due to symptoms. All data was analyzed using stata version 13.0 Result: A total number of 64623 Xpert tests were done. ACF resulted in 1205 MTB positive cases with a higher percentage of cases with low (28.7%) and very low (30.5%) MTB burden and a p value of <0.001 as compared to passive screening which showed greater percentage of cases with high (20.9%) and medium (37.5%) MTB burden. Conclusion: A higher percentage of low MTB burden cases from ACF is clearly suggestive of early case detection, reducing the period of infectiousness and therefore transmission