Nurse-led, protocol-driven penicillin allergy delabelling safe and effective

The nurse-led, protocol-driven Hong Kong Drug Allergy Delabelling Initiative (HK-DADI) is safe and effective for penicillin allergy delabelling, a retrospective study at the Queen Mary Hospital (QMH) has shown.

Patients evaluated through HK-DADI had a similar rate of penicillin allergy delabelling and a higher rate of future penicillin use vs those who underwent traditional allergist-led evaluation. Importantly, in low-risk (LR) patients, nurse-led risk stratification could mitigate the need for unnecessary skin tests (STs), which added no diagnostic value. [J Allergy Clin Immunol Pract 2023;11:474-480.e2]

“Unverified penicillin allergy labels are common [2 percent in Hong Kong] and associated with adverse outcomes. However, most penicillin allergy labels are inaccurate, and the vast majority of patients can tolerate penicillin after appropriate allergy evaluation,” the researchers explained.

The HK-DADI pathway was set up at QMH in 2019 – 2 years after establishment of QMH’s adult Drug Allergy Clinic in 2017 – to triage and counsel patients with suspected penicillin allergy before allergology investigations. After history taking and counselling on penicillin allergy testing, patients were triaged by nurses into LR and non-LR categories based on the pretest likelihood of genuine allergy or anticipated severity of potential reactions. LR patients subsequently attended a dedicated nurse-led LR clinic for STs and, if these were negative, drug provocation test (DPT) in the same clinic session. Non-LR cases were discussed with physicians to confirm clinical status and referred for formal allergist consultation before allergy testing. Selected high-risk patients in both the HK-DADI and traditional pathways underwent in vitro tests before in vivo allergy testing, at the allergist’s discretion.

The current study included data from 312 adult patients who completed penicillin allergy evaluation through the HK-DADI pathway (n=84; mean age, 61 years) between July 2019 and December 2021, or the traditional pathway (n=228; mean age, 57 years) between July 2017 and December 2021.

“Overall, 280 patients [90 percent] had a negative DPT and had penicillin allergy delabelled. No difference in delabelling rates was found between the HK-DADI and traditional pathways [90 percent vs 89 percent; p=0.796],” the researchers reported. “No patients in either pathway developed severe or systemic reactions during penicillin allergy evaluation.”

Among HK-DADI patients, 58 (69 percent) and 26 (31 percent) were triaged as LR and non-LR cases, respectively. Delabelling rate was significantly higher among LR vs non-LR patients (97 percent vs 77 percent; p=0.010), and similar for patients with an index reaction <5 years vs ≥5 years ago (85 percent vs 93 percent; p=0.246).

In contrast, patients evaluated in the traditional pathway were significantly less likely to be delabelled if their index reaction was <5 years vs ≥5 years ago (79 percent vs 95 percent; p<0.001).

Notably, STs did not add diagnostic value among LR patients after nurse-led triage. “There were no positive STs among LR patients. All LR patients with confirmed penicillin allergy were given the diagnosis of a positive DPT after negative STs,” the researchers noted.

Upon follow-up at 6–12 months after delabelling, 123 patients (44 percent) had had infection requiring antibiotics, and 63 (23 percent) had used penicillin after delabelling. The rate of penicillin use was significantly higher in patients delabelled through the HK-DADI vs traditional pathway (32 percent vs 19 percent; p=0.026).

“To date, HK-DADI has managed to shorten the waiting time for a routine penicillin allergy consultation from >7 years to around 1 year. Recognizing its success, the Hospital Authority planned to roll out six additional HK-DADI pathways throughout all regional hospitals in Hong Kong in 2022,” the researchers highlighted.

“Implementation of HK-DADI could potentially save HKD 345 [about USD 44] per penicillin allergy label in ST costs alone,” they added.