Predictors of unfavourable treatment outcome in patients diagnosed with drug-resistant tuberculosis in the Torres Strait / Papua New Guinea border region

Abstract

Drug-resistant tuberculosis (DR-TB) is an ongoing challenge in the Torres Strait / Papua New Guinea border region. Treatment success rates have historically been poor for patients diagnosed with DR-TB, leading to increased transmission and resistance multiplication risk. This study aimed to identify predictors of poor outcome in patients diagnosed with DR-TB to inform programmatic improvements. A retrospective study of all DR-TB cases who presented to Australian health facilities in the Torres Strait between 1 March 2000 and 31 March 2020 was performed. This time period covers four distinct TB programmatic approaches. Univariate and multivariate predictors of poor outcome were analysed. Poor outcome was defined as treatment default, treatment failure and death (versus cure or completion). In total, 133 patients with resistance to at least one TB drug was identified. The vast majority (123/133; 92%) of DR-TB patients had pulmonary involvement; and of these, 41% (50/123) had both pulmonary and extrapulmonary TB. Poor outcomes were observed in 29% (39/133) of patients. Patients living with human immunodeficiency virus, renal disease or diabetes (4/133; 4/133; 3/133) had an increased frequency of poor outcome (p <0.05), but numbers were very small. Among all 133 DR-TB patients, 41% had a low lymphocyte count, which was significantly associated with poor outcome (p <0.05). Overall, outcome improved in recent years with a 50% increase in the chance of a good outcome per year group over the study period; on binary logistic regression analysis. Being a close contact of a known TB case was associated with improved outcome. While DR-TB treatment outcomes have improved over time, it remains important to prevent DR-TB spread and resistance multiplication resulting from suboptimal treatment. Enhanced surveillance for DR-TB, better cross border collaboration and consistent diagnosis and management of comorbidities and other risk factors should further improve patient care and outcomes.