Tuberculosis in cancer patients: Role of newer techniques in relation to conventional diagnostic methods

The highly infectious nature of tuberculosis (TB) urges the need to :increase the efficiency and rapidity of lab methods. The coexistence of TB and cancer was investigated using Mycobacterium tuberculosis direct test (MTD) and the mycobacteria growth indicator tube (MGIT), besides the conventional lab procedures. All assays were performed on 101 patients clinically suspected of having a mycobacterial infection. Over a period of 4 years, TB was confirmed in 32 patients with malignancy by applying the gold standard of considering patients with positive culture on Lowenstein-Jensen or MGIT or having any two or more positive tests as confirmed :mycobacterial infection. Among the confirmed cases, the underlying malignant conditions were hematologic malignancies, bronchogenic carcinoma, and other solid tumors, in 14, 12, and 6 of the patients; respectively. TB developed during cancer chemotherapy in 18 cases (56%), and was discovered synchronously with malignancy in 14 (44%) patients. The ZN stain revealed acid-fast bacilli in 15 (47%) cases. The LJ culture Was positive in 20 (63%) cases and MGIT was positive in 18 (56%) cases. Although the MTD test was positive in 18 (56%) of the confirmed TB cases; i.e., it was negative in 14 cases positive. by other tests. There was a moderate agreement between results of LJ and MGIT, Kappa 0.396 and ZN and MGIT, Kappa 0.436. There was a weak agreement between results of Id and MTD, ZN and MTD, Kappa 0.227 and 0209; respectively; whereas, no agreement was calculated between MGIT and MTD Kappa 0.029. The calculation of the combined sensitivity of any two tests was 94%. TB is a major pathogen in patients with malignant diseases if clinically suspected. Little overlap between different technologies used necessitates the utilization of combination of tests together with consideration of key clinical characteristics to improve the diagnostic accuracy of TB. (C) 2010 Cairo University. All tights reserved.