Incidence, Clinical Predictors and Treatment Outcomes of Necrotizing Otitis Externa: Identifying Regional and Remote Risk in Tropical North Queensland.

Abstract

Objective: To evaluate incidence, presentation, microbiology, and predictors of necrotizing otitis externa (NOE) outcomes in tropical North Queensland, Australia.

Study design: Retrospective cohort study.

Setting: Townsville University Hospital.

Patients: Forty-six NOE patients (January 2017-March 2025).

Interventions: Review of demographic, clinical, and microbiology data. Outcomes stratified by geography (local <50 km vs. regional/remote >50 to >400 km) and indigenous status, with identification of prognostic factors.

Main outcome measures: Incidence, relapse, treatment failure, disease-specific survival, and overall survival per 2024 core outcome set necrotizing otitis externa (COSNOE) guidelines.

Results: A total of 46 patients with NOE were diagnosed between January 2017 and March 2025. Over the 8-year study period, NOE incidence trended higher, peaking at 1.21 per 100,000. Patients were elderly (78 years), male (82.6%), and diabetic (71.7%). Pseudomonas aeruginosa (82.2%) dominated alongside high fungal (64.4%) and polymicrobial (71.1%) infections. Advanced age, cranial neuropathy, and advanced disease predicted adverse outcomes (P < 0.05). Culture-negativity correlated with advanced skull base disease (P = 0.045). Indigenous patients (19.5%) were significantly younger (P < 0.001) with equivalent comorbidity burden (P = 0.719). Overall relapse was 21.7%. C-reactive protein <15 mg/L yielded a 91.3% negative predictive value for recurrence (P = 0.026). Regional/remote residence was an independent predictor of relapse (hazard ratio: 10.47, P = 0.027), yielding a lower relapse-free survival compared with local patients (61.1% vs 88.5%; P = 0.044). Twelve-month treatment success was 80.4%, with 1-year disease-specific mortality 11.1% and overall disease-specific survival 84.7%.

Conclusion: NOE incidence is rising in North Queensland, driven by distinct tropical and social determinants in a high-risk population. With increasing incidence and high relapse rates, further research is required to improve outcomes for high-risk communities.