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and IgM detected in serum are ELISA
tests performed for detection of antibodies
against Mycobacterium tuberculosis
antigens in blood. Depending on the manufacturer, most tets have high senstivity and are considerably specific for detection of tuberculosis. Also, in a so-called endemic country like India, the cut off value is slightly lower than western countries.
So, you can take the test as considerably reliable, done from a good lab, and start treatment depending on your physician's advice.