Safety, Efficacy, and Clinical Impact of Penicillin Skin Testing in Immunocompromised Cancer Patients

Background: Use of penicillin skin testing (PST) to rule out penicillin (PCN) allergies is safe and effective in immunocompetent patients; however, data on immunocompromised patients are limited. Objective: We aimed to determine safety, efficacy, and clinical impact of PST in immunocompromised patients with cancer. Methods: A quality improvement process establishing a PST service was implemented at MD Anderson Cancer Center. Adult patients admitted to leukemia and genitourinary medical oncology (GUMO) services with history of possible type I reactions to PCN were eligible for testing. Results: Between April and October 2017, 218 patients with reported PCN allergies were screened; 100 met inclusion criteria and underwent PST (67 leukemia, 33 GUMO). The most common reported allergy was to PCN (64%), with 61% reporting cutaneous reactions and 79% reporting reactions more than 20 years ago. PST with oral challenge results were overwhelmingly negative (95%); only 4% tested positive, and 1 test result was indeterminate (negative histamine control). After negative PST and oral challenge results, 51% patients were transitioned to PCN-based antibiotics during the same hospitalization. During the follow-up period (median 177 days), 65 of 95 patients were readmitted (185 total readmissions), and 51 patients required antibiotic therapy, with 37 receiving a PCN-based antibiotic (accounting for 336 days of therapy). No patient who received PCN-based antibiotics experienced an immediate-type allergic reaction. Conclusions: Our findings support PST use in immunocompromised hosts. The widespread use of PST in patients with cancer will allow for optimal use of antimicrobial therapy and stewardship, which are vital in a population at increased risk for infections.