Assessment of previous tuberculosis status using questionnaires, chest X-rays and computed tomography scans

SETTING: Accurate diagnosis of previous pulmonary tuberculosis disease (PPTB) status is important clinically and in research. Reliable records of bacteriologically confirmed tuberculosis (TB) are frequently unavailable. OBJECTIVES: To evaluate the use of questionnaires and chest imaging to determine PPTB status in a high TB prevalence population. DESIGN: PPTB status was assessed using two questionnaires, chest X-ray (CXR) and high-resolution chest computed tomography (CT) scans reported by experienced readers. The study population comprised adults aged >40 years diagnosed with obstructive lung disease in a community-based prevalence survey. RESULTS: The Burden of Obstructive Lung Disease (BOLD) questionnaire and a second comprehensive questionnaire (PTbQ) provided a history of PPTB in respectively 38% (n = 41) and 36.4% (n = 39) of 107 participants. On CXR, 43.3% (45/104) had evidence of PPTB, with good inter-reader agreement (kappa = 0.73). Changes compatible with PPTB were identified on chest CT in 68.3% (71/104) of the subjects. Questionnaire and CXR had negative predictive values for PPTB of 48% and 47%, respectively, compared to a composite definition. CONCLUSION: Both questionnaire and CXR markedly underestimate the prevalence of previous TB in patients with chronic obstructive pulmonary disease. The combination of a structured questionnaire and CT scan is more useful when a diagnosis of PPTB needs to be ruled out.