Respiratory samples to diagnose tuberculosis in the absence of chest x-ray abnormalities

The World Health Organisation states that the chest x-ray (CXR) has a 'high sensitivity for pulmonary tuberculosis (TB)' [1] and as such, is relied on worldwide as the cornerstone of screening for active pulmonary TB (pTB).

This is a retrospective analysis of plain chest radiographs and microbiological yield in all patients who were diagnosed with pTB or intra-thoracic nodal tuberculosis (ITLN) in two London NHS Trusts.

Between 2011 and 2017 8% of those diagnosed with pTB and 32% with ITLN TB had normal CXR appearances in the 6 weeks preceding diagnosis.

Pulmomary TB was diagnosed in an additional 51 people based on CT scan and 43 people based on respiratory samples. ITLN TB was also diagnosed in a further 20 people using CT but only an extra 3 people from standard respiratory sampling. Our data suggests that CT imaging and respiratory samples should be sent on all suspected cases of pTB and ITLN TB even if the CXR is normal.