Brief Answer:
Less likely tuberculosis.

Detailed Answer:
Thank you for asking

I read your question and i understand your concern, Old age is for sure immuno compromised enough to be suspected for Tuberculosis, but with already history of acid reflux causing cough and age of 90 with possible other pulmonary troubles like COPD or restrictive fibrotic lungs, tuberculosis is less likely to be the cause. And also in developed countries with no recent TB contact, odds of tuberculosis are very low.

I would suggest considering acid reflux management and supportive and symptomatic treatment and if you still feel like tuberculosis needs to be ruled out, sputum gene expert and simple AFB cultures will sort it out easily.

I hope it helps. Take good care of yourself and dont forget to close the discussion please.

Regards
Khan

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