Prevalence of tuberculosis in close contacts smear positive TB patients

ABSTRACT

Tuberculosis [TB] is considered as one of the main causes of mortality and morbidity in developing countries. At present, extensive contact investigation among households is not a routine part of TB control efforts in most countries. The investigation of contacts of TB cases is an essential part of TB control program. In this study, we have evaluated the active contact tracing among close contacts of smear positive TB patients. The main aim of this research was to demonstrate the prevalence of TB and to fully screen the close contacts of TB patients in order to detect active and infected TB cases. Close contacts of newly diagnosed smear positive pulmonary TB patients were identified. The information and data of the contacts including history, clinical examination, history of BCG vaccination, results of tuberculin skin test [TST], and bacteriological and radiological manifestations were collected on special questionnaires. Out of the total 147 close contacts of 34 index cases, 81 [55.1%] were female and 66 [44.9%] were male. Based on the nationality, there were 38 [25.9%] Afghan refugees and 109 [74.1%] Iranian cases. The duration of contact was as follows in 30 cases the contact time period was less than 1 yr., in 75 individuals it was more than 1 yr., while 42 individuals had a persistent contact. In 61.8% of the cases the induration of TST was less than 15 mm, while in 38.2% it was more than 15 mm. Abnormal radiological manifestations were detected in 33.3% of close contacts including calcification [25.17%], parenchymal infiltration [4.08%], cavity [2.04%] and nodular lesions [2.04%]. According to the diagnostic findings, out of 147 contacts, 7 [4.8%] cases of pulmonary TB were detected. In our study no significant statistical difference was found regarding the prevalence of TB among the Iranian and Afghan close contacts. Also there was no significant statistical difference in the duration of contact time of the TB cases. Furthermore, positive radiological findings were detected in 33.3% of the close contacts. In 25.7% of the cases, the pattern was calcification indicating primary TB infection. According to the results of this research the rate of TB in contacts is 400 times higher than the society [4800/100,000 versus 12/100,000]. This study points out the importance of systematic investigation of contacts to discover new cases of TB. It also demonstrates the significant role of radiology as a major tool in diagnosing both TB infection and disease