Sometimes it may happen don't worry your doctor is the best judge, as per my opinion he should send a pleural fluid for advanced test for culture and drug sensitivity to rule out resistant tuberculosis he should look for other causes of effusion like auto immune diseases and cardiac cause and renal cause malignant cells, of he is very sure that's it TB he should tap all the fluid and add some steroid as TB fluid is a reaction to bacterial cell wall causing inflammation reaction and fluid collection steroid stops that reaction and allows regression of fluid accumulation fast.