A case of persistent IgE sensitisation almost two decades following ampicillin anaphylaxis.

BACKGROUND: Although most immunoglobulin E (IgE)-mediated penicillin allergy wanes with time, sensitisation may occasionally persist for many years. Previous reports on the loss of penicillin-specific IgE sensitisation were based on non-anaphylaxis cases and, although uncommon, persistent sensitisation may still be possible in the minority of cases. OBJECTIVE: This case highlights that irrespective of the elapsed duration since the index reaction, it is important to remain vigilant when approaching patients with a history of severe reactions. MATERIAL AND METHODS: We described a case of persistent IgE sensitisation almost two decades following ampicillin anaphylaxis. RESULTS: A 78-year-old male with a history of perioperative penicillin anaphylaxis in 2003 was referred for allergy workup in 2022 before his knee joint replacement surgery. The patient had strictly avoided all beta-lactams since the index reaction. However, his penicillin-specific sensitisation persisted, evidenced by positive skin tests (with generalised urticaria after intradermal testing) and basophil activation tests. CONCLUSION: To our knowledge, this was the first case of positive BAT tested around two decades following the index reaction. This case illustrates that a cautious approach may still be warranted in patients with a history of severe reaction to penicillin regardless of the duration since the reported index reaction.

COVID-19 Vaccine Allergy Safety Track (VAS-Track) pathway: real-world outcomes on vaccination rates and antibody protection.

BACKGROUND: Misdiagnosed vaccine-related "allergies" lead to unnecessary vaccine deferrals and incomplete vaccinations, leaving patients unprotected against COVID-19. To overcome limitations and queues for Allergist assessment, the "VAS-Track" pathway was developed to evaluate patients via a multi-disciplinary triage model including nurses, non-specialists, and Allergists. OBJECTIVE: We assessed the effectiveness and safety of VAS-Track and evaluate its real-world impact in terms of vaccination rates and COVID-19 protection. METHODS: Patients referred to VAS-Track between September 2021 and March 2022 were recruited. Subgroup analysis was performed with prospective pre- and post-clinic antibody levels. RESULTS: Nurse-assisted screening identified 10,412 (76%) referrals as inappropriate. 369 patients were assessed by VAS-Track. Overall, 100% of patients were recommended to complete vaccination and 332 (90%) completed their primary series. No patients reported any significant allergic reactions following subsequent vaccination. Vaccination completion rates between patients seen by non-specialists and additional Allergist review were similar (90% vs. 89%, p = 0.617). Vaccination rates were higher among patients with prior history of immediate-type reactions (odds ratio: 2.43, p = 0.025). Subgroup analysis revealed that only 20% (56/284) of patients had seropositive COVID-19 neutralizing antibody levels (≥ 15 AU/mL) prior to VAS-Track, which increased to 92% after vaccine completion (pre-clinic antibody level 6.0 ± 13.5 AU/mL vs. post-clinic antibody level 778.8 ± 337.4 AU/mL, p > 0.001). CONCLUSIONS: A multi-disciplinary allergy team was able to streamline our COVID-19 VAS services, enabling almost all patients to complete their primary series, significantly boosting antibody levels and real-world COVID-19 protection. We propose similar multidisciplinary models to be further utilized, especially in the settings with limited allergy services.

Skin prick testing a better predictor than blood testing for the diagnosis of peanut allergy in Chinese children.

BACKGROUND: Peanut allergy is common in Chinese children, yet the most predictive diagnostic cut-offs for skin prick test (SPT) and blood testing in this population are unclear. OBJECTIVES: We aimed to determine the optimal cut-off values for whole-peanut SPT, specific IgE (sIgE) and component-resolved diagnostics (CRD) for Chinese children based on outcomes of open oral food challenges (OFC) to peanut. METHODS: We recruited ethnic-Chinese patients 1-18 years old who were suspected of having peanut allergy based on a history of reactions after exposure or sensitization although peanut naïve. Considering the AUC value of 0.8, 80% power and 5% level of significance with two tails, 26 patients were needed. Sensitivities, specificities, positive and negative predictive values, and receiver operating characteristic curves (ROCs) and their area-under-curves (AUCs) for SPT, peanut sIgE, and CRD were compared. RESULTS: Thirty-one subjects participated. Only SPT reached statistical significance (AUC 0.91, p = 0.0001), but not the other tests. Seven retrospective data were added to optimize the power. SPT remained to be the best predictor, followed by Ara h 2 sIgE (AUC 0.72, p = 0.02). An SPT wheal size of 3 mm and Ara h 2 sIgE of 0.14 kU(A)/L yielded the highest Youden's index. The specificity of SPT and Ara h 2 sIgE reached 94% at 6 mm and 0.74 kU(A)/L, respectively. Comparisons of ROCs revealed that SPT was significantly better than Ara h 2 sIgE (p = 0.03) and whole-peanut sIgE (AUC 0.61, p = 0.26). CONCLUSION: In Chinese children, SPT appeared to be the best predictor for peanut allergy, followed by Ara h 2 sIgE.

Piperacillin-Tazobactam Allergies: An Exception to Usual Penicillin Allergy.

PURPOSE: The majority of penicillin allergy labels are false, and skin tests (ST) have high negative predictive value (NPV) of up to 90%. Piperacillin-tazobactam (PT) allergy has been suspected to be an exception to this, but existing literature is scarce. We investigate the epidemiology, clinical characteristics, testing outcomes and predictive value of ST in patients referred for suspected PT allergies. METHODS: The records of all patients referred for suspected PT allergy testing and prescription rates of PT in all Hong Kong public hospitals (2015-2019) were analyzed. RESULTS: There was an increase in both PT prescriptions and number of newly reported PT allergies between 2015 and 2019. The majority (91.1%) of patients with suspected PT allergy had at least 1 underlying medical co-morbidity or immunosuppressant use leading to increased risk of infections. Thirty-six patients with suspected PT allergy completed ST. Two patients had positive ST, and 32/34 patients with negative ST underwent drug provocation testing (DPT). Nine of these patients were diagnosed with PT allergy based on positive DPT. Overall, 11/34 (32.4%) were diagnosed with PT allergy and the NPV of ST was 71.9%. CONCLUSIONS: There is growing utilization of PT and corresponding cases of suspected allergies. The majority of suspected PT allergies had increased risk for recurrent infections. Unlike other penicillin allergy, there is a high rate of genuine PT allergy (up to 30%) and a poor NPV of ST (up to 70%). DPT remains the gold standard for accurate diagnosis, and all patients with a suspected allergy should undergo thorough allergy workup.