Data collection
Baseline demographic data (i.e. date of birth, age, weight, height, body mass index (BMI), body surface area (BSA), cystic fibrosis transmembrane conductance regulator (CFTR) mutation type), APE data (i.e. date of hospital admission, diagnosis, severity, per cent predicted forced expiratory volume in one second (ppFEV1), microbial reports, white blood cell count and c-reactive protein count) and antibiotic data (i.e. tobramycin treatment duration, dose, plasma levels of tobramycin and concomitant antibiotic treatment) were collected. Data regarding outcomes included APE recurrence, hospital length of stay, increased levels of creatinine and bacteremia duration. Severity of the APE was assessed using the Matouk Score (10), a modified version of the Huang score, because of its systematic use at our center. All data was collected by manual review of the local electronic database.