Multidrug resistant tuberculosis versus non-tuberculous mycobacterial infections: a CT-scan challenge

Clinical, laboratory and imaging findings in patients with multidrug resistant-tuberculosis (MDR-TB) and non-tuberculosis mycobacterium (NTM) are similar, and the majority of these patients present with positive smear for Acid Fast Bacilli (ADB) and no response to first line anti-TB treatment, so sputum culture and PCR are necessary, especially in NTM.

In this study we evaluate more details of imaging findings to help earlier diagnosis of pathogens.

66 patients with positive smear for AFB and no response to first line anti-TB drugs were divided into two groups by PCR and culture: MDR-TB (43 patients) and NTM (23 patients). Age, sex, history of anti-TB treatment, smoking and CT-scan findings (parenchymal, pleural and mediastinal variables) by details and lobar distribution were analyzed.

Mean age of NTM patients was slightly higher (52 versus 45) and there is no significant difference in sex and smoking. In MDR-TB group, history of anti-TB treatment and evidence of chronic pulmonary disease such as calcified and fibrodestructed parenchyma, volume loss and pleural thickening were higher significantly. Cavities in MDR-TB were thick-wall in the background of consolidation, while NTM cavities were more thin-walled with adjacent satellite nodules in same segment or lobe. Prevalence of bronchiectasis was similar in both groups, while bronchiectasis in MDR-TB group was in fibrobronchiectatic background in upper lobes, and in NTM group the distribution was more uniform with slightly middle lobes predominance. Prevalence and distribution of nodular infiltrations were similar more in Tree in Buds and scattered pattern. Calcified or non-calcified lymph nodes and also pleural changes were more frequent in MDR-TB but prevalence of lymphadenopathy was mildly higher in NTM.

A check-list with multiple variables is helpful for differentiation between the two groups.