To challenge or not to challenge: Literature data on the positive predictive value of skin tests to beta-lactams

Diagnostic performance of serial serum total tryptase measurement to differentiate positive from negative allergy testing among patients with suspected perioperative hypersensitivity

BACKGROUND

Serum total tryptase has been shown to increase during acute allergic reactions (acute tryptase, T_A ); however, few studies have investigated the values of T_A or a combination of T_A and baseline tryptase (T_B ) to discriminate positive from negative testing in perioperative hypersensitivity reaction (POH) allergy work up. The aim of this study was to determine the diagnostic performance of T_A in order to differentiate positive from negative allergy testing suspected POH and analyze the diagnostic performance of serial tryptase levels using several formulas.

METHODS

All patients from the University hospital of Montpellier and Strasbourg, France who presented with suspected POH and underwent complete drug allergy work-up between March 2011 and December 2019 with available T_A and T_B were included. Four formulas, including a change in T_A >11 (F1), or >2+1.2xT_B (F2), or >3+T_B (F3), or >120%T_B (F4), were applied.

RESULTS

One hundred and sixty-two patients were included, and 131 of them (80.8%) had grade III or IV reactions. Ninety patients had positive allergy testing. The optimal cut-off value of T_A to distinguish positive from negative allergy testing patients was 9.8 μg/L with an AUC of 0.817 (95%CI: 0.752-0.882, p<0.001). The 93% PPV threshold for T_A was 33 μg/L (95.8% specificity). Paired tryptase levels according to formulas F2 and F3 yielded the highest Youden index (0.54 and 0.53, respectively).

CONCLUSION

The optimal cut-off point for T_A for distinguishing positive from negative allergy testing suspected POH was 9.8 μg/L. T_A value of 33 μg/L was required to achieve >90% PPV.

Practical guide for evaluation and management of beta-lactam allergy: position statement from the Canadian Society of Allergy and Clinical Immunology

The vast majority of individuals labelled as allergic are not deemed truly allergic upon appropriate assessment by an allergist. A label of beta-lactam allergy carries important risks for individual and public health. This article provides an overview of beta-lactam allergy, implications of erroneous beta-lactam allergy labels and the impact that can be provided by structured allergy assessment. We provide recommendations on how to stratify risk of beta-lactam allergy, beta lactam challenge protocols as well as management of patients at high risk of beta-lactam allergy.

Accuracy of penicillin allergy diagnostic tests: A systematic review and meta-analysis

BACKGROUND

Having a penicillin allergy label associates with a higher risk for antibiotic resistance and increased health care use.

OBJECTIVE

We sought to assess the accuracy of skin tests and specific IgE quantification in the diagnostic evaluation of patients reporting a penicillin/β-lactam allergy.

METHODS

We performed a systematic review and diagnostic accuracy meta-analysis, searching on MEDLINE, Scopus, and Web of Science. We included studies conducted in patients reporting a penicillin allergy and in whom skin tests and/or specific IgE quantification were performed and compared with drug challenge results. We quantitatively assessed the accuracy of diagnostic tests with bivariate random-effects meta-analyses. Meta-regression and subgroup analyses were performed to explore causes of heterogeneity. Studies' quality was evaluated using QUADAS-2 criteria.

RESULTS

We included 105 primary studies, assessing 31,761 participants. Twenty-seven studies were assessed by bivariate meta-analysis. Skin tests had a summary sensitivity of 30.7% (95% CI, 18.9%-45.9%) and a specificity of 96.8% (95% CI, 94.2%-98.3%), with a partial area under the summary receiver-operating characteristic curve of 0.686 (I² = 38.2%). Similar results were observed for subanalyses restricted to patients reporting nonimmediate maculopapular exanthema or urticaria/angioedema. Specific IgE had a summary sensitivity of 19.3% (95% CI, 12.0%-29.4%) and a specificity of 97.4% (95% CI, 95.2%-98.6%), with a partial area under the summary receiver-operating characteristic curve of 0.420 (I² = 8.5%). Projected predictive values mainly reflect the low frequency of true penicillin allergy.

CONCLUSIONS

Skin tests and specific IgE quantification appear to have low sensitivity and high specificity. Because current evidence is insufficient for assessing the role of these tests in stratifying patients for delabeling, we identified key requirements needed for future studies.

Premedication for Iodinated Contrast Media Induced Immediate Hypersensitivity Reactions

Purpose of the review

Premedication using antihistamines and/or corticosteroids has been widely used to prevent reoccurrence of immediate hypersensitivity reactions (iHR) after iodinated contrast media (ICM). However, efficacy has been debated, especially in high-risk patients. Novel findings on the role and risks of premedication and preventive strategies are summarized.

Recent findings

The rate and severity of iHR occurring despite premedication indicate that premedication is not a panacea and the intensity usually reflects that of the initial reaction. Next, the number needed to treat (NNT) to prevent one serious ICM-mediated event using corticosteroid-based premedication is high and associated with a diagnostic delay. Randomly changing the ICM has been suggested as an additional preventive measure, whilst others used a skin test–based approach to identify a subgroup of ICM allergic patients and negative skin test–based alternatives with a high negative predictive value.

Summary

Growing evidence indicates the need to discriminate between non-allergic iHR that are most likely non-obligatory and susceptible to premedication, and rare type I allergic iHR that can be identified using skin testing, especially in those with a severe iHR. Although premedication reduces reoccurrence of mild iHR, it is not always efficacious and should be balanced against side effects, a high NNT and an uncertain efficacy physicians should not blindly rely on. Future work should evaluate combined approaches of an allergy-driven ICM selection and endotype-driven premedication regimens in patients with non-allergic iHR.