<prompt> A patient was sputum negative for TB, but chest Xray was suggestive for TB. Which is the next step according to RNTCPLiquid cultureCB - NAATLine probe assayNone of the above  <response>: Reference:Technical and Operational guidelines for TB control in India 2016 DIAGNOSTIC ALGORITHM FOR TB:All presumptive TB will undergo sputum smear examinationIf first sputum Is smear positive and not at risk of DR -TB, it will be categorised as microbiologically confirmed TBFor Smear positive and presumptive MDR-TB , CB-NAAT will be performed to rule out Rifampicin resistance, and categorised as microbiologically confirmed drug sensitive RIF resistant TBIf first smear is negative and chest X ray is suggestive of TB, 2nd sample will be subjected to smear and CB-NAAT simultaneouslyCB NAAT is Cartridge Based Nucleic Acid Amplification TestThe Gene expert TB test detects DNA sequences specific for M.Tuberculosis and Rifampicin resistance by PCR.It is based on Cepheid Gene expert system , a platform for rapid and simple to use nuclei acid amplification tests NAAT.Results are obtained within 90 minutes. It has minimal biohazard and needs very little technical training since unprocessed sputum samples are used to identify the results in a realtime format. 