Objectives
  • Disseminate info on TB in India
  • Improve care of TB patients in India
  • Enable doctors and NGO's interested in TB control to interact

Diagnosis of Tuberculosis

Radiological diagnosis

doctor seeing xray It is not uncommon to come across patients who have been started on antitubercular chemotherapy relying solely on Xray examination ,neglecting sputum examination or ignoring the results.Juvekar et al(In J Tub 1998,45,95) in a paper designed to study prospectively the help seeking patterns and treatment behaviour of patients of pulmonary tuberculosis diagnosed in the clinics of private medical practitioners observed that only 10% of urban and 21% rural patients were subjected to sputum examination before diagnosis. A majority of patients -78% urban and 56% rural reported to have undergone an X-ray examination only, before the diagnosis of TB was made by their practitioner.Jagota(Ind J Tub 1998,45,3) stated .." even after decades of functioning of the National Tuberculosis programme over diagnosis due to excessive use of X-rays was enormous and only 20% of the patients diagnosed in the district were confirmed by sputum examination. The efficacy of chest radiography is determined largely by the reader's ability to detect abnormal opacities and interpret them and conversely not categorising non tubercular or normal films as tubercular.

Several studies have shown that persons with lung shadows in X-ray of chest but no previous history of tuberculosis and in whom tubercle bacilli could not be demonstrated by smear microscopy (or culture wherever available)particularly when repeated are in fact rarely true cases of tuberculosis The following table will help to understand the eventualities:
History of previous treatment X-ray positive
Sputum positive Sputum negative
Nil Fresh case of PT Non tubercular aetiology to be ruled out
Adequate Relapse, mostly drug sensitive Inactive PT
Inadequate Further ATT needed(Drug resistance to be kept in mind) Further ATT needed
There are 3 possibilities in the patients having an X-ray shadow suggestive of Tuberculosis but sputum is negative

  1. No previous history of TB The lesions may be non tubercular or early TB or some forms like Pleural effusion,miliary or primary complex.In these cases if feasible additional investigations like Mantoux,Bronchoscopy,examination of pleural fluid are likely to give clues
  2. Previous history of adequate antitubercular treatment The present symptoms may be due to sequelae like bronchiectasis,aspergillosis etc.
  3. Previous history of inadequate antitubercular treatment Altough sputum is negative antitubercular treatment should be restarted.
The corresponding eventualities in the presence of positive sputum are:
  1. No previous history of TB These are fresh cases of TB and tackled as such
  2. Previous history of adequate antitubercular treatment ( ie adequate duration and appropriate regimen)If sputum has previously been positive,the diagnosis need not be called into question;In these cases it is important to get full details of previous treatment. These cases have to be dealt with as relapses. Chemotherapy studies have shown that about 80% of relapses are with drug sensitive organisms, hence chemotherapy can be restarted with primary drugs via INH,Rifampicin,Pyrazinamide
  3. Previous history of inadequate antitubercular treatment The treatment should be restarted and a full course completed.Detailed guidelines exist in revised national TB control programme on how to tackle cases with interruption of chemotherapy
Thus a careful history including previous examination and treatment results, and sputum examination are crucial to determine the correct management of suspected cases. Blind reliance on X-ray findings only needs to be discouraged.