Prevalence of Drug-Resistant Mycobacterium tuberculosis in the Veterans Health Administration (VHA)

Abstract

Background: In 2018, the CDC reported that isoniazid (INH)-resistant and multidrug-resistant Mycobacterium tuberculosis (MDR-TB, ie, resistant to at least INH and rifampin) represented 9.3% and 1.5% of TB cases, respectively, in the United States. Objective: We analyzed the prevalence of drug-resistant TB within the Veterans Health Administration (VHA) to determine factors associated with hospitalization. Method: Patients were identified using Council of State and Territorial Epidemiologists case definition for laboratory-confirmed TB by querying VHA data sources from January 1, 2010, to June 30, 2019. Susceptibility results were included for isolates from all body sites. Using a 2-proportion z test, we compared the following demographic factors for susceptible versus drug-resistant TB: age, gender, race/ethnicity, location of residence and birth. We also assessed the following clinical and hospitalization factors: pulmonary versus extrapulmonary disease, latent TB infection (LTBI) screening and treatment, length of stay (LOS), intensive care unit (ICU) stay, and death. Results: In total, 878 patients had lab-confirmed TB, and 812 (92%) had electronic drug-susceptibility results available. Of 812 patients, 49 (6%) showed anti-TB drug resistance (Fig. 1), which was less than that reported nationally by the CDC (Fig. 2). No patients had extensively drug-resistant TB. Only 18 of 49 patients (37%) with resistant TB had LTBI screening ≥3 months prior to diagnosis. Among 6 patients with LTBI, 3 (50%) received treatment. Patient state of residence was the only demographic factor associated with resistant TB. Arizona, Iowa, Massachusetts, Montana, Nevada, South Dakota, and Utah were significantly associated with drug-resistant TB cases (P < .05); however, overall numbers of VHA TB cases in these states were low. Patients with resistant TB were more likely to have extrapulmonary TB (13 of 49, 26.5%) than patients with susceptible TB (111 of 763, 14.5%; P < .05) (Table 1). Mortality at 30 and 90 days for resistant versus susceptible TB cases did not differ significantly: 6.1% versus 5.1% at 30 days (P = .75) and 10.2% versus 10.6% at 90 days (P = 0.92), respectively. The proportion of drug-resistant TB cases hospitalized did not differ from susceptible cases (59% vs 63%), respectively (P = .62) nor did the proportion with ICU stay (14.3% vs 12.3%), respectively (P = .40). Median LOS for drug-resistant TB cases and susceptible cases were similar: 5 days (range, 0–303 versus 4 days (range, 0–111), respectively. Conclusions: Rates of drug-resistant TB are lower in the VHA than in the general US population. However, improvement is needed in LTBI screening and treatment rates. Little has been published on drug resistance in extrapulmonary TB; however, our findings should alert clinicians to the possibility of resistance in these challenging infections.Funding: NoneDisclosures: None