Diagnosis of pulmonary tuberculosis: recent advances.

India continues to have the highest number of TB cases in the world, and over 2 million cases are reported in India every year. The private sector in India is an important source of TB care with over 50% of TB patients seeking TB treatment in the private health sector. Early and accurate diagnosis is the first critical step in controlling TB. All persons with cough lasting two weeks or more, or with unexplained chronic fever and/or weight loss should be evaluated for TB. For pulmonary TB, Sputum is the most critical sample for laboratory testing. Although blood is a popular sample in the Indian private sector, there is no accepted, valid blood test for pulmonary TB. There are three accepted, validated sputum tests for active TB: Sputum smear microscopy for acid-fast bacilli; molecular or nucleic acid amplification test (NAAT); and culture. Chest radiography is useful but is not specific for the diagnosis of pulmonary TB. Therefore, chest radiography cannot provide a conclusive diagnosis on its own, and needs to be followed by sputum testing. If sputum smears and NAATs are negative, and TB is still suspected, cultures are the most sensitive tests available for TB. Culture is therefore very useful in diagnosing smear-negative TB; and drug-resistant TB. Blood-based antibody tests (eg, IgG/IgM tests) and Interferon-gamma release assays (eg, TB Gold) are not accurate and should not be used for pulmonary TB diagnosis. In fact, use of serodiagnostic tests for TB is banned by the Government of India.