Brief Answer:
Treatment is based on presumptive diagnosis.

Detailed Answer:
Dear XXXX,
Hi & Welcome to HCM.

I appreciate your concerns for the anti TB treatment with negative lab tests.

Sometimes if all the lab tests fail to demonstrate the presence of TB germs and hence are found to be negative, the treatment in such patients is based upon the general condition and the clinical examination.

Regarding sputum examination:

A patient is said of sputum positive if the causative TB organisms are found in his sputum. However, not all patients suffering from lung TB emit organisms. In about 50% cases, even repeated sputum tests would fail to demonstrate any germs. These cases are sputum negative cases.

Regarding Chest X-rays:

Presence of abnormal shadows in Chest X-rays is an indirect evidence of infection. A negative Chest x ray does not rule out the disease.
Therefore, diagnosis by X-ray alone is unreliable.
A series of chest X-rays is much more helpful than a single picture.

Regarding Tuberculin skin test:

It has some diagnostic value in small children; the smaller the child, stronger the positive skin reaction – the higher the probability of active disease.

In adults in our country it is almost of no practical value in adults and is rarely employed.

Positive test is suggestive of presence of infection rather than active disease.
A positive test doesn’t confirm TB sickness.
A negative test doesn’t rule it out.

However, in a some cases, a physician has no option but to resort to a presumptive diagnosis and start TB treatment based on his experience. In your case this is the situation and you have already responding to the treatment is it not?

So, adhere to the treatment as prescribed by your doctor.

Hope to have answered your query.
Wishing you a very good health.

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