Impact of Antibiotic Treatment Duration on Clinical Outcomes in Acute Mastoiditis

Corresponding Author Krista Stacey, MD; staceyk@chop.edu Funding None. Conflict(s) of Interest None. Background The optimal antibiotic treatment duration for acute mastoiditis is unknown, with 2-4 weeks recommended by the American Academy of Pediatrics. Methods We performed a comparative effectiveness study of short versus long antibiotic duration in children aged 6 months to 18 years with acute mastoiditis admitted to Children’s Hospital of Philadelphia (CHOP) between January 2016 and December 2023. Children with an ICD-10 diagnosis code for acute mastoiditis were included if they received at least 7 days of antibiotics for clinician-diagnosed mastoiditis and had both clinical and radiographic findings of acute mastoiditis based on physician chart review. Children with severe immunodeficiencies, cochlear implants, chronic mastoiditis (symptoms >1 month), non-bacterial causes of mastoiditis, and those with epidural or subdural abscesses were excluded. The primary exposure was short-course antibiotics, defined as an antibiotic duration of approximately 2 weeks (up to 17 days). The primary outcome was treatment failure, defined as a composite of mastoiditis-related readmission, reoperation, or antibiotic re-treatment within 30 days of completing antibiotic treatment. Antibiotic-associated adverse events were assessed as a secondary outcome. Propensity scores were derived to estimate the probability of receiving short-course antibiotics, then used to generate inverse probability of treatment weights (IPTW). Covariate balance was assessed using standardized mean differences (SMD), with SMD less than 0.1 considered balanced. Weighted logistic regression was then used to calculate odds of treatment failure. Results A total of 126 children were included. Median age was 4 years (IQR, 2, 8 years), 104 (85%) were previously healthy, 53 (43%) had a subperiosteal or subcutaneous abscess, and 66 (52%) underwent a surgical procedure. Sixty-two (49%) received a short duration of antibiotics (median, 14 days; IQR 11, 15 days) and 64 (51%) received a long duration of antibiotics (median 24 days; IQR 21, 28 days). The composite outcome was observed in 7 children (6%), including 2 children (3%) in the short-course group and 5 children (8%) in the long antibiotic duration group (p=.25). Following propensity score weighting, baseline covariates were well-balanced across treatment groups (Fig. 1). The odds of treatment failure with short-course antibiotics in the weighted cohort was 0.49 (95% confidence interval, 0.08-2.96). Antibiotic-associated adverse events occurred more often in the long antibiotic duration group, but this difference did not reach statistical significance (8% versus 16%, p=.18). Conclusion A short duration of antibiotics of approximately 2 weeks was not associated with increased odds of treatment failure relative to a longer duration in children with acute mastoiditis without intracranial complications.