Targeted active screening for tuberculosis in Zimbabwe: are field digital chest X-ray ratings reliable?

SETTING: Fifteen purposively selected districts in Zimbabwe in which targeted active screening for tuberculosis (Tas4TB) was conducted among TB high-risk groups (HRGs). There were 230 patients started on TB treatment on the basis of chest X-ray (CXR) results without corresponding bacteriological confirmation. OBJECTIVES: To determine 1) the percentage of agreements in digital CXR ratings by medical officers against final ratings by radiologist(s), 2) inter-rater agreement in CXR ratings between medical officers and radiologists, and 3) number (and proportion) of patients belonging to HRGs who were over-treated during Tas4TB. DESIGN: This was a cross-sectional study using programme data. RESULTS: A total of 168 patients had their CXRs rated by two independent radiologists. Discordances among the radiologists were resolved by a third index radiologist, who provided the final rating. κ scores were 0.01 (field ratings vs. Radiologist A); 0.02 (field ratings vs. Radiologist B); 0.74 (Radiologists A vs. B). The percentage agreement for field and final radiologist rating was 70% (95%CI 64-78). Around 29% (95%CI 23-36) of the patients were potentially over-treated during Tas4TB. CONCLUSION: Over a quarter of patients with presumptive TB are potentially over-treated during Tas4TB. Over-treatment is highest among those with previous contact with TB patients. Trainings of radiographers and medical officers may improve CXR ratings.

A comparison of the yield and relative cost of active tuberculosis case-finding algorithms in Zimbabwe.

SETTING: Ten districts and three cities in Zimbabwe. OBJECTIVE: To compare the yield and relative cost of identifying a case of tuberculosis (TB) using the three WHO-recommended algorithms (WHO2b, symptom inquiry only; WHO2d, chest X-ray [CXR] after a positive symptom inquiry; WHO3b, CXR only) and the Zimbabwe active case finding (ZimACF) algorithm (symptom inquiry plus CXR) to everyone. DESIGN: Cross-sectional study using data from the ZimACF project. RESULTS: A total of 38 574 people were screened from April to December 2017; 488 (1.3%) were diagnosed with TB using the ZimACF algorithm. Fewer TB cases would have been diagnosed with the WHO-recommended algorithms. This ranged from 7% fewer (34 cases) with WHO3b, 18% fewer (88 cases) with WHO2b and 25% fewer (122 cases) with WHO2d. The need for CXR ranged from 36% (WHO2d) to 100% (WHO3b). The need for bacteriological confirmation ranged from 7% (WHO2d) to 40% (ZimACF). The relative cost per case of TB diagnosed ranged from US$180 with WHO3b to US$565 for the ZimACF algorithm. CONCLUSION: The ZimACF algorithm had the highest case yield, but at a much higher cost per case than the WHO algorithms. It is possible to switch to algorithm WHO3b, but the trade-off between cost and yield needs to be reviewed by the Zimbabwean National TB Programme.

Mobile targeted screening for tuberculosis in Zimbabwe: diagnosis, linkage to care and treatment outcomes.

SETTING: Targeted active screening for tuberculosis (Tas4TB) using mobile trucks in the community was implemented in 15 high TB burden districts in Zimbabwe. At-risk populations were screened for TB based on symptoms and chest radiography (CXR) results. Those with any positive symptom and/or an abnormal CXR had sputum collected for investigation and diagnosis and were linked to care and treatment if found to have TB. OBJECTIVE: To determine 1) the proportion and characteristics of those screened and diagnosed with TB; 2) the relationship between TB symptoms, CXR and diagnostic yields; and 3) the relationship between initiation of anti-TB treatment and treatment outcomes. DESIGN: Cohort study using routinely collected data. RESULTS: A total of 39 065 persons were screened, of whom 663 (1.7%) were diagnosed with TB; 126/663 (19.0%) were bacteriologically confirmed. The highest TB diagnostic yields were in symptomatic persons with CXRs suggestive of TB (19.4%), asymptomatic persons with CXRs suggestive of TB (8.4%) and persons at high-risk of TB (3.2%). For all diagnosed TB patients, pre-treatment loss to follow-up was 18.9% and treatment success was 59.9%. CONCLUSION: Tas4TB resulted in high diagnostic yields; however, linkage of diagnosis to care was poor. Reasons for loss to follow-up need to be better understood and rectified.