Self-Reported Penicillin Allergy and antibiotic use in critical care: An observational, retrospective study

Patients with Self-Reported Penicillin Allergy (SRPA) receive alternative antibiotics, which increase the length of stay and hospital costs, but the impact of SRPA on mortality in critically ill patients is not well described.

This was a single-center, retrospective analysis of routinely gathered clinical data for all intensive care unit (ICU) admissions over nine years. The primary outcome was 28-day mortality, which was analyzed using a time-to-event approach with multivariable models to adjust for confounding factors, including age, comorbidities, sex, and admission SOFA score (as a measure of organ dysfunction). Antibiotic prescriptions during the ICU stay were also interrogated and compared.

Of 35,319 admissions, 11.7% had SRPA. Compared with non-SRPA, patients with SRPA were more likely to be female (52.2% vs. 37.4%, p < 0.001) and had more comorbidities (p < 0.001) but had similar admission SOFA scores (median: 3.5 in both groups, p = 0.839). Patients with SRPA had significantly lower 28-day mortality (9.6% vs. 10.9%, p = 0.011). After multivariable adjustment for baseline characteristics, this effect persisted for unplanned (hazard ratio [HR]: 0.76, 95% CI: 0.68-0.86, p < 0.001), but not planned admissions (HR: 1.21, 95% CI: 0.92-1.58, p = 0.172). Whilst the duration of antibiotics in ICU was similar in the SRPA and non-SRPA groups (mean: 3.4 vs. 3.4 days, p = 0.663), the antibiotics used differed, with SRPA patients being significantly more likely to receive quinolones or other anti-Gram-positive antibiotics (p < 0.001).

SRPA was associated with a survival benefit that persisted after adjustment for confounders for unplanned ICU admissions. Patients with SRPA were more likely to receive antibiotics that are not active against anaerobic bacteria.