Background: Evaluation of patients with suspected tuberculosis and negative sputum smears for acid-fast bacilli (AFB) is challenging, especially in high human immunodeficiency virus coinfection settings where sputum smears have lower sensitivity for detecting AFB.
Methods: We examined the utility of chest radiographs for detecting smear-negative pulmonary tuberculosis. Three hundred sixty sputum smear-negative patients who were referred from primary care clinics in the KwaZulu-Natal province of South Africa were evaluated. Chest radiographs were read by experienced pulmonologists using a previously validated Chest X-Ray Reading and Recording System (CRRS).
Results: Agreement between observers using CRRS was high at 91% with a Cohen's kappa of 0.64 (95% confidence interval [CI] = 0.52-0.76). Against a reference standard of sputum culture, sensitivity was 93% (95% CI = 86%-97%), whereas specificity was 14% (95% CI = 10%-19%). Performance against clinical diagnosis (following World Health Organization guidelines) was similar with sensitivity of 92% (95% CI = 88%-95%) and specificity of 20% (95% CI = 13%-28%).
Conclusion: The low specificity of CRRS in this setting indicates poor diagnostic utility for detecting pulmonary tuberculosis.
Keywords: South Africa.; chest radiograph; smear-negative; tuberculosis.