Antimicrobial allergy 'labels' drive inappropriate antimicrobial prescribing: lessons for stewardship

Background: The presence of antimicrobial allergy designations (`labels') often substantially reduces prescribing options for affected patients, but the frequency, accuracy and impacts of such Labels are unknown. Methods: The National Antimicrobial Prescribing Survey (NAPS) is an annual de-identified point prevalence audit of Australian inpatient antimicrobial prescribing using standardized definitions of guideline compliance, appropriateness and indications. Data were extracted for 2 years (2013-14) and compared for patients with an antimicrobial allergy Label (AAL) and with no AAL (NAAL). Results: Among 21031 patients receiving antimicrobials (33421 prescriptions), an AAL was recorded in 18%, with inappropriate antimicrobial use significantly higher in the AAL group versus the NAAL group (OR 1.12, 95% CI 1.05-1.22, P<0.002). Patterns of antimicrobial use were significantly influenced by AAL, with Lower B-Lactam use (AAL versus NAAL; OR 0.47, 95% CI 0.43-0.50, P<0.001) and higher quinolone (OR 2.07, 95% CI 1.83 2.34, P<0.0001), glycopeptide (OR 1.59, 95% CI 1.38-1.83, P<0.0001) and carbapenem (OR 1.74, 95% CI 1.43-2.13, P<0.0001) use. In particular, among immunocompromised patients, AAL was associated with increased rates of inappropriate antimicrobial use (OR 1.68, 95% CI 1.21-2.30, P=0.003), as well as increased use of quinolones (OR 1.88, 95% CI 1.16-3.03, P=0.02) and glycopeptides (OR 1.82, 95% CI 1.17-2.84, P=0.01). Conclusions: AALs are common and appear to be associated with higher rates of inappropriate prescribing and increased use of broad-spectrum antimicrobials. Improved accuracy in defining AALs is Likely to be important for effective antimicrobial stewardship (AMS), with efforts to 'de-Label' inappropriate AAL patients a worthwhile feature of future AMS initiatives.