Drug allergy labels and complications after surgery: a prospective multicentre cohort study.

BACKGROUND: One in four surgical patients carries a drug allergy label, of which an estimated 90% are incorrect. Avoidance of first-choice drug therapies can lead to worse postoperative outcomes. We sought to determine the nature and extent of any association between drug allergy labels and postoperative complications. METHODS: A multicentre observational study was performed in 21 UK National Health Service hospitals. Eligible patients were ≥18 yr of age and undergoing common surgical procedures: primary hip or knee replacement, internal fixation of closed long bone fracture, colorectal resection, transurethral resection of prostate or bladder tumour, Caesarean delivery, or hysterectomy. Exclusion criteria were the use of antibiotics in the two weeks before surgery or previous participation in the study. The primary outcome was postoperative complications within 30 days after surgery, a composite outcome comprising all postoperative infections, anastomotic leak, acute respiratory distress syndrome, myocardial infarction, postoperative bleeding, pulmonary embolism, stroke, antimicrobial side-effects, and death. RESULTS: Among 13 646 patients, 3924 (29%) carried ≥1 drug allergy label. Labelled patients were more likely to develop postoperative complications (989/3924 [25%] vs 1926/9722 [20%]; odds ratio [OR] 1.21 [1.10-1.34]; P<0.001). They were more likely to develop surgical site infections (337/3924 [9%] vs 760/9722 [8%]; OR 1.19 [1.03-1.38]; P<0.018), and any postoperative infection (750/3924 [19%] vs 1472/9722 [15%]; OR 1.24 [1.11-1.38]; P<0.001). Labelled patients experienced an increased risk of allergic drug reactions (31/3924 [0.01%] vs 29/9722 [<0.01%]; OR 3.00 [1.77-5.09]; P<0.001), but no increase in mortality. CONCLUSIONS: Drug allergy labels are common, but often incorrect. Patients with drug allergy labels experience worse postoperative outcomes, including infective and noninfective complications and an increased risk of allergic drug reactions. TRIAL REGISTRATION: ISRCTN Registry (ISRCTN15775657).