Accuracy of classification of notified tuberculosis cases in Taiwan

SETTING: Tuberculosis (TB) suspects and cases reported in 2003 in Taiwan. OBJECTIVES: To evaluate the accuracy of the classification of notified TB cases in Taiwan. DESIGN: A list of all TB cases reported in 2003 in Taiwan was obtained from the Taiwan Center for Disease Control, along with their classification. TB cases residing in Taipei City were investigated by consulting their medical charts. RESULTS: Of 1973 patients, 782 (39.6%) were bacteriologically confirmed, 1024 (52%) were not bacteriologically confirmed (indeterminate) and 167 (9%) were not TB cases (in whom non-tuberculosis mycobacteria [NTM] was isolated). Of the 1973 cases, 1716 (87%) had been treated with anti-tuberculosis drugs, while 257 (13%) had not been treated. Of the 782 bacteriologically confirmed cases, 68 (8.7%) were misclassified as non-notifiable (32 [4.1%] had their diagnosis changed by a clinician and 36 [4.6%] by administrative coding). Of the 167 cases in whom NTM were isolated, 72 (43.1%) were misclassified as TB cases. Of the 257 untreated suspects, 31 (12.1%) did not have any evidence of TB (20 indeterminate and 11 NTM cases) and were questionably classified as newly diagnosed cases. CONCLUSION: There was substantial misclassification of notified TB cases in Taiwan.