IMPORTANCE Cefazolin is the preoperative antibiotic of choice because it is safer and more efficacious than second-line alternatives. Surgical patients labeled as having penicillin allergy are less likely to prophylactically receive cefazolin and more likely to receive clindamycin or vancomycin, which results in higher rates of surgical site infections.OBJECTIVE To examine the incidence of dual allergy to cefazolin and natural penicillins.DATA SOURCES MEDLINE/PubMed, Web of Science, and Embase were searched without language restrictions for relevant articles published from database inception until July 31, 2020.STUDY SELECTION In this systematic review and meta-analysis, a search of MEDLINE/PubMed, Web of Science, and Embase was performed for articles published from database inception to July 31, 2020, for studies that included patients who had index allergies to a natural penicillin and were tested for tolerability to cefazolin or that included patients who had index allergies to cefazolin and were tested for tolerability to a natural penicillin. A total of 3228 studies were identified and 2911 were screened for inclusion.DATA EXTRACTION AND SYNTHESIS Data were independently extracted by 2 authors. Bayesian meta-analysis was used to estimate the frequency of allergic reactions. MAIN OUTCOMES AND MEASURESDual allergy to cefazolin and a natural penicillin. RESULTSSeventy-seven unique studies met the eligibility criteria, yielding 6147 patients. Cefazolin allergy was identified in 44 participants with a history of penicillin allergy, resulting in a dual allergy meta-analytical frequency of 0.7% (95% credible interval [CrI], 0.1%-1.7%; I 2 = 74.9%). Such frequency was lower for participants with unconfirmed (0.6%; 95% CrI, 0.1%-1.3%; I 2 = 54.3%) than for those with confirmed penicillin allergy (3.0%; 95% CrI, 0.01%-17.0%; I 2 = 88.2%). Thirteen studies exclusively assessed surgical patients (n = 3884), among whom 0.7% (95% CrI, 0%-3.3%; I 2 = 85.5%) had confirmed allergy to cefazolin. Low heterogeneity was observed for studies of patients with unconfirmed penicillin allergy who had been exposed to perioperative cefazolin (0.1%; 95% CrI, 0.1%-0.3%; I 2 = 13.1%). Penicillin allergy was confirmed in 16 participants with a history of cefazolin allergy, resulting in a meta-analytical frequency of 3.7% (95% CrI, 0.03%-13.3%; I 2 = 64.4%). The frequency of penicillin allergy was 4.4% (95% CrI, 0%-23.0%; I 2 = 75%) for the 8 studies that exclusively assessed surgical patients allergic to cefazolin.CONCLUSIONS AND RELEVANCE These findings suggest that most patients with a penicillin allergy history may safely receive cefazolin. The exception is patients with confirmed penicillin allergy in whom additional care is warranted.

Background: Data are limited regarding the incidence of thromboembolism post-hospital discharge among COVID-19 patients. Guidelines addressing the role of extended thromboprophylaxis for COVID-19 patients are limited and conflicting. Objective: The purpose of this study was to evaluate the incidence of post-discharge thromboembolic and bleeding events and the role of thromboprophylaxis among COVID-19 patients. Methods: A retrospective analysis was conducted of hospitalized patients with symptomatic COVID-19 infection who were discharged from a University of Colorado Health (UCHealth) hospital between March 1, 2020, and October 31, 2020. The primary outcome was objectively confirmed thromboembolism within 35 days post-discharge. The main secondary outcome was the incidence of bleeding events within 35 days post-discharge. Outcomes were compared between those who received extended prophylaxis and those who did not. Results: A total of 1171 patients met the study criteria. A total of 13 (1.1%) of patients had a documented thromboembolic event and 10 (0.9%) patients had a documented bleeding event within 35 days post-discharge. None of the 132 patients who received extended prophylaxis had a thromboembolic event compared to 13 of 1039 who did not receive extended prophylaxis (0 and 1.3%, respectively; P = .383). The incidence of bleeding was higher among patients who received extended prophylaxis compared to those who did not (3.0% vs 0.6%, P = .019). Conclusions and Relevance: These results suggest that post-discharge extended prophylaxis may be beneficial for select COVID-19 patients, while carefully weighing the risk of bleeding. Application of our findings may assist institutions in development of thromboprophylaxis protocols for discharged COVID-19 patients.