Available data from longitudinal study (1961-68) from several different situations have been reviewed to understand the significance of patients showing radiological evidence of pulmonary tuberculosis without bacteriological confirmation. SITUATION IN GENERAL POPULATION: Few of the smear negative but X-ray active tuberculous patients (suspect cases) found in a survey of rural population done by National TB Institute, were culture positive (7-10%). On follow up for 18 months, only 3% of them became culture positive under conditions where intervention with specific treatment was absent or minimum. It is thus concluded that most of the cases diagnosed as active tuberculosis on the basis of single X-ray are not likely to be cases of tuberculosis. SITUATION AMONG SYMPTOMATICS ATTENDING HEALTH INSTITUTIONS: Data from the State TB Demonstration and Training Centres (STDTC) and the District Tuberculosis Programmes (DTP) have been presented. The New Delhi Tuberculosis Centre records (1970) show that only 27% of microscopy negative radiologically positive patients were confirmed on culture. For Bangalore and Agra STDTC, the proportions so confirmed were 20% and 25% respectively. It has been calculated that in the DTPs, not more than 30% of the microscopy negative radiologically positive patients could be the real cases of tuberculosis. In the DTP situation not more than 10% of the suspect cases may develop bacteriologically confirmed disease. Thus, not many of the suspect cases could be real cases of tuberculosis either on the basis of confirmation by culture or on the basis of development of bacteriologically positive disease in future.

Are the cases diagnosed ‘early’ by radiology? The hypothesis that X-ray discovers cases in the early stages has not yet been put to a scientific test. Further, the large differences even between experienced readers in interpreting X-ray shadows, render the method of X-ray diagnosis questionable. Is anti tuberculosis treatment of suspect cases warranted? The possible advantage of considering treatment of suspect cases as chemoprophylaxis has to be weighed against conservation of resources for treatment of infectious cases and the possible harmful effects of anti TB drugs to persons who are not suffering from tuberculosis.