A patient was sputum negative for TB, but chest Xray was suggestive for TB. Which is the next step according to RNTCP
Reference:Technical and Operational guidelines for TB control in India – 2016
 
DIAGNOSTIC ALGORITHM FOR TB:

All presumptive TB will undergo sputum smear examination
If first sputum Is smear positive and not at risk of DR -TB, it will be categorised as microbiologically confirmed TB
For 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 TB
If first smear is negative and chest X ray is suggestive of TB, 2nd sample will be subjected to smear and CB-NAAT simultaneously
CB NAAT is Cartridge Based Nucleic Acid Amplification Test


The 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.
Liquid culture
CB - NAAT
Line probe assay
None of the above