To determine accuracy of the ELISA in detecting IgG TB antibodies using 16kDa and 38kDa antigens for the diagnosis of Pulmonary Tuberculosis.METHOD: Validation of ELISA as a diagnostic test for PTB compared with culture, histo-pathology and clinical follow-up.SETTING: Chest clinic practice, tertiary university hospital in Metro-Manila.PARTICIPANTS: TB suspects by WHO/NTP-DOH criteria: all patients over age 15 with cough of over 2 weeks, prolonged fever, weight loss, normal or abnormal chest x-rays; OR, all patients with abnormal chest x-rays who had diagnostic work-up like bronchoscopy, thoracotomy and pleural or lung biopsy.INTERVENTION: Patients completed clinical examination, mantoux test, and x- ray; a single specimen of sputum, lung aspirate, pleural and lung biopsies were submitted for AFB smears and Bactec culture; biopsy specimens were submitted for histo-pathology; serum samples were frozen at −20°C in coded cryo-vials for batch analysis by ELISA using 16KDa and 38KDa diagnostic kits. Laboratory and pathologist were not aware of the clinical diagnosis. Disease classification was independently assessed based on a modified ATS TB Classification for Disease Status by attending pulmonologist.OUTCOMES MEASURES: Demographic profiles, tests results, TB disease categorization based on clinical course; sensitivity, specificity, PPVs, LRs were derived.
At 46% TB disease prevalence, serology has 58.6% sensitivity, 96.3% specificity, 93.1% PPV, 73.3% NPV, 15.8 LR+ and 0.43 LR-.
The test is highly specific with a high positive predictive value and significant likelihood ratios.CLINICAL IMPLICATION: Using combined antigens, serology can be a useful diagnostic tool in the diagnosis of PTB.
B.D. Briones, None.