Methods: This quasi-experimental study compared an experimental group of 100 adult patients who completed PST for a self-reported penicillin allergy over an open enrollment period beginning January 2016 to a matched control group of 100 patients over the same time frame that had a listed penicillin allergy as well as consultation with infectious diseases. Patients in the control group were matched to the infection diagnosis codes of the members of experimental group and then randomly selected and matched on a 1:1 basis. The primary outcome was beta-lactam days of therapy (DOT) defined as either a penicillin or cephalosporin (not carbapenem). The secondary outcome assessed the average cost of antimicrobial therapy before and after PST.
Results: The control group consisted of 436 patients who met inclusion criteria with 100 patients from that group matched to the 100 patients in the PST group by diagnosis code. The most common self-reported allergy consisted of IgE-mediated (52%) and unknown (30%) in the PST group and IgE-mediated (33%), unknown (20%), and rash (32%) in the control group. Ninety-eight of 100 patients who underwent PST tested negative, with 71 out of 98 (73%) having changes directly made to their antimicrobial regimens immediately after PST. Beta-lactam DOT for the PST group were 666 out of 1094 (60.88%, with 34.82% being a penicillin specifically). Beta-lactam DOT for the control group consisted of 386 out of 984 (39.64%, with 6.4% being a penicillin specifically). Chi-square test of homogeneity for beta-lactam DOT between the two groups was significant (P < .00001). Changes to the antimicrobial regimen after PST saved the average patient $353.03 compared to no change in pre-PST regimen (P = .045).
Conclusion: PST led to immediate antimicrobial de-escalation in the majority of patients who tested negative. This led to a significant increase in beta-lactam usage, specifically penicillins. These benefits were also associated with significant cost savings to patients, justifying the cost of performing PST.
B. M. Jones,
J. Crosby, None
C. Bland, ALK: Grant Investigator and Speaker's Bureau , Grant recipient and Speaker honorarium .