792. Number and Volume of Cavitary Lesions on Chest Computed Tomography Associated With Prolonged Time to Culture Conversion in Drug-Susceptible Pulmonary Tuberculosis

BACKGROUND: Cavitary lesions (CLs) may be a marker of poor treatment response in pulmonary tuberculosis (PTB). Identification of CLs by chest roentgenogram (CXR) has important limitations. Chest computed tomography (CT) is more sensitive than CXR to detect CLs but the clinical relevance of CLs identified by CT remains understudied. We compared detection of CLs between CT and CXR and assessed their association with time to sputum culture conversion (tSCC). We hypothesized that increasing number and volume of CLs on CT would be associated with prolonged tSCC. METHODS: Retrospective cohort study of 141 culture confirmed PTB patients who underwent chest CT. We used multivariate Cox proportional hazards models to evaluate the association between chest radiological features and tSCC. RESULTS: Seventy-five (53%) patients had one or more CLs on CT. CT identified cavities in 31% of patients without a CL on CXR. Detection of cavity on CT was associated with an increased median [IQR] time to culture conversion (15 [7–35] days among noncavitary CT vs. 39 [25–55] days among cavitary CT; P < 0.0001). Among patients without CL on CXR, detection of CL on CT was associated with prolonged tSCC (median difference (CI): 16 (7–25) days, P = 0.0008). Similar results were observed among patients with 3–4+ sputum smear (median difference: 19.5 (8–31) days, P = 0.001). Adjusted Kaplan–Meier curves of number and volume of CLs and tSCC are shown in Figure 1. After confounder adjustment patients with single and multiple CL had a prolonged tSCC relative to patients without CLs on CT (adjusted Hazard Ratio [aHR] 0.56 (0.32–0.97) and 0.31 (0.16–0.60), respectively). Similarly, patients with CL volume 25 mL or more had a prolonged tSCC (aHR 0.39 (0.21–0.72)). CXR CL was not associated with prolonged tSCC. CONCLUSION: We observed a dose–response relationship between increasing number and volume of CLs on CT and delayed tSCC independent of sputum bacillary load. Our findings highlight a role for CT in a clinical research setting to predict shorter time to culture conversion. [Image: see text] DISCLOSURES: All authors: No reported disclosures.