Authors (including presenting author) :
Li PH(1), Chan TS(1), Chiang V(2), Wong JCY(1), Ho CTK(1), Au EYL(2), Lau CS(1)
Affiliation :
(1)Division of Rheumatology and Clinical Immunology, Department of Medicine, Queen Mary Hospital, The University of Hong Kong, (2) Division of Clinical Immunology, Department of Pathology, Queen Mary Hospital
Introduction :
Unverified penicillin allergies are common, with 1 in 50 people in Hong Kong labelled with suspected "allergies" in their medical records. However, most drug allergy labels to penicillin are inaccurate, and the vast majority of patients can tolerate penicillins after appropriate allergy evaluation (>85% of penicillin allergy labels in Hong Kong have shown to be inaccurate!). A label of penicillin allergy has been associated with a myriad of adverse outcomes, such as the use of less effective antibiotic alternatives, increased mortality and hospitalization, higher health care costs, and the development of multidrug-resistant microorganisms. Thus, appropriate penicillin allergy delabeling has been advocated as an important public health initiative to improve patient outcomes and antimicrobial stewardship.
Despite the overwhelming benefits of delabelling incorrect penicillin allergy labels, there is a severe shortage of allergists and allergy services in Hong Kong. Traditionally, evaluation of suspected penicillin allergy includes history taking, skin tests (STs) (including skin prick tests [SPTs] and intradermal tests [IDTs]), and drug provocation tests (DPTs). Although penicillin STs have a negative predictive value of above 90%, DPT remains the reference standard and is
needed to confirm tolerance of penicillins confidently after a negative ST. However, this traditional pathway of penicillin allergy evaluation with consultation, ST, and DPT for every patient can be costly, time-consuming and, moreover, requires specialist input.
Unfortunately, there is still only one Specialist in Immunology & Allergy in the entire Hospital Authority who leads other physicians and trainees of the drug allergy clinic at Queen Mary Hospital (QMH). With this severe shortage, the waiting time for a routine penicillin allergy consultation at QMH was over 7 years prior to implentiation of any intervention. Therefore, new diagnostic strategies to overcome the overwhelming burden and lack of allergy specialist services in Hong Kong are urgently needed.
We devised a novel nurse-led, protocol-driven allergy evaluation to streamline the entire process of incorrect pencillin allergy delabelling - the Hong Kong Drug Allergy Delabelling Initiative (HK-DADI). Based on a similar multidisciplinary approach to our successful coronavirus disease 2019 Vaccine Allergy Safety clinics, HK-DADI is a protocol-driven evaluation run by trained nurses, designed to triage and counsel patients with suspected penicillin allergy before allergologic investigations.
Objectives :
This study was performed to evaluate the effectiveness, safety, and real-world outcomes of a nurse-led penicillin allergy evaluation system - HK-DADI. Allergy and postdelabeling outcomes were compared between patients evaluated via HK-DADI or a traditional allergist evaluation.
Methodology :
QMH began a formal adult Drug Allergy Clinic service in 2017 and receives referrals for suspected drug allergy from the whole of Hong Kong. Between 2017 and 2019, a traditional allergist led evaluation pathway (traditional pathway) was in place before HK DADI. All referrals received for suspected penicillin allergy were sequentially queued for allergist consultation at QMH.
The HK DADI pathway was set up in QMH in 2019. Thereafter, all patients referred for suspected penicillin allergy would first be interviewed by a trained nurse based a protocol driven approach. After history taking and counseling on penicillin allergy testing, patients would be triaged into low risk (LR) and nonelow risk (NLR) based on the pretest likelihood of genuine allergy or the anticipated severity of potential reactions. Low risk patients subsequently attended a dedicated nurse led LR clinic in which penicillin STs and, if those were negative, DPTs would be performed in the same clinic session. Triage decisions and interpretations of patients’ clinical status were based on the professional judgment of nurses, who were fully supported by an overseeing physician. No allergist review was required for LR patients under the HK DADI pathway. On the other hand, NLR cases were discussed with physicians to confirm NLR status and were investigated as per traditional pathway by an allergist.
Regardless of evaluation pathway, all patients were routinely contacted again (in person or via telephone interview) around 6 to 12 months after the completion of allergy testing and their medical records were reviewed. Data regarding longitudinal outcomes, such as subsequent episodes of infections requiring antibiotics, penicillin use, and personal confidence in taking penicillin, were collected and analyzed. All follow up clinical data, as well as prescription data, were retrieved and cross referenced with the Hospital Authority’s unified electronic Clinical Management System.
We retrospectively analyzed the demographic and longitudinal clinical data of all patients who completed penicillin allergy evaluation (through either the traditional or HK DADI pathways) between 2017 and 2021. Data from patients from the traditional pathway were from July 2017 to December 2021, and those from the HK DADI pathway were from July 2019 to December 2021. Only patients who had completed penicillin allergy evaluation (ie, with positive allergy tests or negative DPTs) were included for analysis. All patients gave informed consent. This study was approved by the Institutional Review Board of HKU/HKWC.
Result & Outcome :
In total, 312 patients completed penicillin allergy evaluation during the study period: 84 (27%) and 228 (73%) via the HK-DADI and traditional pathways, respectively. There were no statistically significant differences in demographic
or clinical characteristics. Overall, 280 patients (90%) had a negative DPT and had their incorrect penicillin allergies delabeled. The delabeling rate between HK-DADI and traditional pathways was similar (90% vs 89%; P=0.796). Among patients of the HK-DADI pathway, the delabeling rate was significantly higher among low-risk (LR) compared with non-LR patients (97% vs 77%; P=0.010). Skin tests did not add diagnostic value among LR patients. No patients developed severe or systemic reactions during the evaluation. Waiting time was cut from over 7 years to 1 year.
All patients of both the HK-DADI and traditional pathways were reviewed 6 to 12 months after delabeling (median interval, 10 months). Overall, 223 (80%) self-reported that they were confident in using penicillin again in the future. There was no difference between patients delabeled via the HK-DADI and traditional pathways (82% vs 79%; P=0.623). Almost half (123; 44%) had experienced infective episodes that required antibiotic prescriptions, and 63 (23%) had used penicillins again since delabeling. No patients reported allergic reactions after reexposure to penicillins. In
subgroup analysis, significantly more patients delabeled via the HK-DADI subsequently used penicillins compared with patients of the traditional pathway (32% vs 19%; P=0.026).
The Hong Kong Drug Allergy Delabelling Initiative represents a novel multidisciplinary risk-stratifying approach using the combined expertise of nurses and physicians to streamline penicillin allergy testing among Chinese patients - the first such study in the world. We demonstrate that a nurse-led, protocol-driven evaluation was safe and effective in penicillin allergy delabeling. We also found that nurse-led evaluation led to an even higher rate of future penicillin use after delabeling and could mitigate the need for unnecessary STs among LR patients.
More nurse-led and multidisciplinary initiatives should be employed to alleviate the overwhelming demand for allergy services. Therefore, based on the positive experiences and findings from this study, several novel HK-DADI clinics have been set up since mid-2022 across the various clusters of the Hong Kong Hospital Authority. Furthermore, Hong Kong has now established our own local consensus statements for penicillin allergy testing by non-allergists, leading the world in multi-disciplinary-based penicillin allergy delabeling.
