High sensitivity of chest radiograph reading by clinical officers in a tuberculosis prevalence survey

BACKGROUND: Chest radiographs (CXRs) are used in tuberculosis (TB) prevalence surveys to identify participants for bacteriological examination. Expert readers are rare in most African countries. In our survey, clinical officers scored CXRs of 19216 participants once. We assessed to what extent missed CXR abnormalities affected our TB prevalence estimate. METHODS: Two experts, a radiologist and pulmonologist, independently reviewed 1031 randomly selected CXRs, mixed with films of confirmed TB cases. CXRs with disagreement on 'any abnormality' or 'abnormality consistent with TB' were jointly reviewed during a consensus panel. We compared the final expert and clinical officer classifications with bacteriologically confirmed TB as the gold standard. RESULTS: After the panel, 199 (19%) randomly selected CXRs were considered abnormal by both expert reviewers and another 82 (8%) by one reviewer. Agreement was good among the experts (kappa 0.78, 95%CI 0.73-0.82) and moderate between the clinical officers and experts (kappa range 0.50-0.62). The sensitivity of 'any abnormality' was 95% for the clinical officers and 83% and 81% for the respective experts. The specificities were respectively 73%, 74% and 80%. TB prevalence was underestimated by 1.5-5.0%. CONCLUSIONS: Acceptable CXR screening can be achieved with clinical officers. Reviewing a sample of CXRs by two experts allows an assessment of prevalence underestimation.