Optimizing the Diagnostic Approach to Cephalosporin Allergy Testing

Background:

In the United States, beta-lactam antibiotics are the leading cause of allergic reactions. Cephalosporin antibiotics, in particular, are the most common cause of drug-induced anaphylaxis and perioperative allergy. For penicillin allergy, the mechanism of allergy and the antigenic determinants are known; validated penicillin skin testing followed by drug challenge has a 100% negative predictive value to exclude an immunoglobulin (Ig)E-mediated reaction. For cephalosporin allergy, the antigenic determinants and mechanism are not known, and skin testing is not validated. The diagnostic test characteristics of skin testing with native cephalosporins remain unclear with no sensitivity nor specificity reported. Although beta-lactam cross-reactivity has been hypothesized to be from the similarity of the R1 side chains, rather than the beta-lactam ring, cross-reactivity estimates among beta-lactams vary. Furthermore, it is not known whether the variance in cross-reactivity is due to true allergy versus sensitization based on positive skin testing, given that drug challenges were not performed on skin-test-positive patients. While an IgE mechanism is assumed for cephalosporin allergy and supported by skin testing that has been positive, the biology has yet to be characterized, and some cephalosporin anaphylaxis can occur on the first exposure, which is inconsistent with an IgE mechanism. Given the complexity of cephalosporin structures and potential epitopes, there may be several distinct biologic pathways involved in cephalosporin allergy. Future diagnostics in cephalosporin allergy are reliant on determination of these biological pathways and finding key haptens.

Aims:

Current national practice guidelines related to cephalosporin allergy assessment are conditional and based on low-quality evidence. The overall goal is to identify the optimal diagnostic approach to cephalosporin allergy and determine beta-lactam cross-reactivity, while discovering the mechanism and antigenic determinants of cephalosporin allergy to advance future diagnostics. The investigators will do this through a clinical trial that will generate empirical evidence through novel trial procedures, double-blind skin testing, and double-blind placebo-controlled drug challenges. Specific aims are: 1) To determine the optimal approach to cephalosporin allergy evaluation; 2) To assess beta-lactam cross-reactivity in cephalosporin-allergic individuals; and 3) To investigate the antigenic determinants and mechanism of cephalosporin allergy.

Study Overview:

Enrolled and consented subjects will attend Visit 1 for baseline screening, sample collection, double-blind skin testing to a beta-lactam panel, and a double-blind placebo-controlled challenge to their culprit cephalosporin antibiotic. Results of the culprit cephalosporin challenge determine subject's study timeline. Subjects confirmed as non-allergic to their culprit cephalosporin will return for the End-of-Study Visit for venipuncture and blood collection, ending their participation in the study. Subjects who are confirmed as allergic to their culprit at Visit 1 will return for three additional visits; Visits 2 and 3 will include double-blind placebo-controlled challenges to a similar side chain and dissimilar side chain cephalosporin (as compared to the side chain of their culprit) to assess cross-reactivity. The order of these two challenges is randomized between Visit 2 and 3, and the order of whether a similar or dissimilar side chain cephalosporin is challenged first (in Visit 2) differentiates the comparator arms of this study. In Visit 4, subjects from both comparator arms will undergo a double-blind placebo-controlled challenge to a penicillin to assess cross-reactivity between cephalosporins and penicillins. After completion of this penicillin challenge, confirmed-allergic participants will return for an End-of-Study Visit. This visit will mark the end of their participation in the study. Venipuncture and sample collection will occur at each visit.

• Beta-lactam antibiotic (cefazolin, cefuroxime, cefotaxime, ceftazidime, ceftriaxone, cefepime, pre-pen, penicillin G, ampicillin, and histamine) double-blind skin testing (Drug): Percutaneous and intradermal skin testing will be performed in all participants. Concentrations for percutaneous testing; cefazolin (330 mg/ml), cefuroxime (90 mg/ml), ceftazidime (100 mg/ml), ceftriaxone (100 mg/ml), cefepime (200 mg/ml), pre-pen (undiluted), penicillin G (10,000 U/ml), ampicillin (20 mg/ml) and histamine (6 mg/ml). Concentrations for the first intradermal testing; cefazolin (3.3mg/ml), cefuroxime (1 mg/ml), ceftazidime (1 mg/ml), ceftriaxone (1 mg/ml), cefepime (2 mg/ml), Pre-PEN (undiluted), penicillin G (1000 U/ml), ampicillin (20 mg/ml), and histamine (0.1 mg/ml). Concentrations for the second intradermal testing; cefazolin (33mg/ml), cefuroxime (10 mg/ml), ceftazidime (10 mg/ml), ceftriaxone (10 mg/ml), cefepime (20 mg/ml), Pre-PEN (undiluted), penicillin G (10,000 U/ml), ampicillin (20 mg/ml) and histamine (0.1 mg/ml). Histamine and saline will be used as positive and negative controls.
• Culprit cephalosporin (cefazolin, ceftazidime, ceftriaxone, cefepime, cephalexin, cefaclor, cefadroxil, cefuroxime, cefpodoxime, cefdinir, or cefixime) double-blind placebo-controlled drug challenge (Drug): After double-blind skin testing, participants will undergo a 3-step double-blind placebo-controlled drug challenge to their culprit cephalosporin (the cephalosporin they are suspected to be allergic to, either cefazolin, ceftazidime, ceftriaxone, cefepime, cephalexin, cefaclor, cefadroxil, cefuroxime, cefpodoxime, cefdinir, or cefixime). The challenges are 1:1 randomized to the order of active drug versus placebo. In Step 1, participants will receive 1:1000 of a full dose of either the culprit drug or placebo, followed by a 30-minute observation period. In Step 2, participants will receive 1:50 of a full dose of either, followed by another 30-minute observation period. In Step 3, participants are administered the full dose of either agent, followed by a 60-minute observation period. The same testing process is repeated for the second challenge.
• Similar cephalosporin (cefepime, ceftriaxone, cefaclor, cephalexin, cefixime, or cefdinir) antibiotic double-blind placebo-controlled drug challenge (Drug): Participants will undergo a 3-step double-blind placebo-controlled drug challenge to a cephalosporin antibiotic that shares a similar side chain with their culprit. This will be cefepime for those allergic to ceftriaxone, cefaclor for those allergic to cephalexin, cefixime for those allergic to cefdinir, cefdinir for those allergic to cefixime, cephalexin for those allergic to cefaclor or cephadroxil, and ceftriaxone for those allergic to cefepime, cefuroxime, or cefpodoxime. The challenges are 1:1 randomized to the order of active drug versus placebo. In Step 1, participants will receive 1:1000 of a full dose of either the culprit drug or placebo, followed by a 30-minute observation period. In Step 2, participants will receive 1:50 of a full dose of either, followed by another 30-minute observation period. In Step 3, participants are administered the full dose of either agent, followed by a 60-minute observation period. The same testing process is repeated for the second challenge.
• Dissimilar cephalosporin (ceftriaxone or cefazolin) antibiotic double-blind placebo-controlled drug challenge (Drug): Participants will undergo a 3-step double-blind placebo-controlled drug challenge to a cephalosporin antibiotic that has a dissimilar side chain to their culprit. This will be ceftriaxone for those allergic to cefazolin, and cefazolin for those allergic to any other cephalosporin. The challenges are 1:1 randomized to the order of active drug versus placebo. In Step 1, participants will receive 1:1000 of a full dose of either the culprit drug or placebo, followed by a 30-minute observation period. In Step 2, participants will receive 1:50 of a full dose of either, followed by another 30-minute observation period. In Step 3, participants are administered the full dose of either agent, followed by a 60-minute observation period. The same testing process is repeated for the second challenge.
• Amoxicillin double-blind placebo-controlled drug challenge (Drug): Participants will optionally undergo a 3-step double-blind placebo-controlled drug challenge to Amoxicillin. The challenges are 1:1 randomized to the order of active drug versus placebo. In Step 1, participants will receive 1:1000 of a full dose of either the culprit drug or placebo, followed by a 30-minute observation period. In Step 2, participants will receive 1:50 of a full dose of either, followed by another 30-minute observation period. In Step 3, participants are administered the full dose of either agent, followed by a 60-minute observation period. The same testing process is repeated for the second challenge. The order of challenge to similar vs. dissimilar cephalosporin will be randomized as well.

Primary outcomes

• Proportion of participants with confirmed culprit cephalosporin allergy [Up to 7 weeks]: Placebo-controlled drug challenges will be used to confirm or disprove participant's cephalosporin allergies, and the proportion of included participants with confirmed allergies will be measured.
• Cephalosporin skin test sensitivity and specificity [Up to 7 weeks]: Challenge results will be used as a reference standard to determine the sensitivity and specificity of cephalosporin skin testing.
• Proportion of cross-reactivity to other cephalosporins in confirmed-allergic subjects [Up to 7 weeks]: The proportion of participants with confirmed cross-reactivity to dissimilar/similar cephalosporins than their culprit will be determined.

Secondary outcomes

• Culprit cephalosporin skin test diagnostic characteristics [Up to 7 weeks]: The diagnostic testing characteristics of culprit cephalosporin skin tests will be evaluated, including positive predictive value (PPV), negative predictive value (NPV), and false positive rate.
• Cephalosporin skin test diagnostic characteristic performance differences between risk groups [Up to 7 weeks]: Allergy history risk will be measured using a validated Drug Allergy History Tool. The PPV, NPV, and false positive rate of skin testing will then be compared through regression modeling to show differences in diagnostic characteristic performance between high-risk and low-risk groups.
• Association between patient demographics and confirmed cephalosporin allergy [Up to 7 weeks]: Participant demographic traits will be collected and their associations with confirmed cephalosporin allergy will be presented as odds ratios with 95% confidence intervals.
• Association between patient allergy history and confirmed cephalosporin allergy [Up to 7 weeks]: A validated Drug Allergy History Tool will be used to collect participant's allergy history, and associations of allergy history with confirmed cephalosporin allergy will be presented as odds ratios with 95% confidence intervals.
• Proportion of nocebo responders [Up to 7 weeks]: The rate of nocebo response in those undergoing cephalosporin drug challenges will be measured.
• Cephalosporin-specific antibody levels [Up to 54 months]: Cephalosporin drug- and hapten-specific antibody levels will be evaluated from serum using ELISA.
• Cephalosporin-specific antibody binding [Up to 54 months]: Cephalosporin drug antibody binding epitopes will be presented using nanoallergens to evaluate rates of antibody binding and cell degranulation to gain a mechanistic understanding of cephalosporin allergy.

Other outcomes

• Prevalence of nocebo response [Up to 7 weeks]: The prevalence of nocebo responses to drug challenges will be measured to understand how often these responses occur during cephalosporin challenges.
• Graded severity of nocebo response reactions [Up to 7 weeks]: Respiratory, mucocutaneous, and cardiovascular symptoms and clinical presentation of nocebo response reactions will be collected and graded using the United States Drug Allergy Registry (USDAR) grading scale to determine the average severity of nocebo reactions. This scale is scored as either NR (no reaction) or values 0-4 indicating the severity of the reaction, with 0 being the mildest and 4 being the most severe.
• Cephalosporin skin test clinical statistics [Up to 7 weeks]: The average diameter size of the wheal and flare during cephalosporin skin tests will be determined.
• Tryptase levels in those with confirmed allergy [Up to 7 weeks]: In participants with confirmed cephalosporin allergy, tryptase levels will be evaluated and compared to determine if tryptase levels are associated with reaction grades.
• Amoxicillin cross-reactivity in those with confirmed cephalosporin allergy [Up to 7 weeks]: Among those with confirmed cephalosporin allergy, the proportion with cross-reactivity to amoxicillin will be determined.
• Amoxicillin skin test diagnostic characteristics in those with confirmed cephalosporin allergy [Up to 7 weeks]: Among those with confirmed cephalosporin allergy, the skin test diagnostic characteristics with amoxicillin will be determined, including positive predictive value (PPV), negative predictive value (NPV), and false positive rate.
• Similar cephalosporin skin test diagnostic characteristics in participants with confirmed cephalosporin allergy [Up to 7 weeks]: Among those with confirmed cephalosporin allergy, the skin test diagnostic characteristics with a similar side-chain cephalosporin will be determined, including positive predictive value (PPV), negative predictive value (NPV), and false positive rate.
• Dissimilar cephalosporin skin test diagnostic characteristics in participants with confirmed cephalosporin allergy [Up to 7 weeks]: Among those with confirmed cephalosporin allergy, the skin test diagnostic characteristics with a dissimilar side-chain cephalosporin will be determined, including positive predictive value (PPV), negative predictive value (NPV), and false positive rate.
• Graded severity of cephalosporin allergic reactions [Up to 7 weeks]: Respiratory, mucocutaneous, and cardiovascular symptoms and clinical presentation of cephalosporin allergic reactions will be collected and graded using the United States Drug Allergy Registry (USDAR) grading scale to determine the average severity of cephalosporin reactions. This scale is scored as either NR (no reaction) or values 0-4 indicating the severity of the reaction, with 0 being the mildest and 4 being the most severe.
• Proportion of delayed hypersensitivity reactions to cephalosporins [Up to 7 weeks]: The proportion of participants with delayed hypersensitivity reactions to cephalosporins will be recorded.
• Incidence of adverse events with cephalosporin diagnostic tests [Up to 7 weeks]: The incidence rate of allergic and nonallergic adverse events (as graded by the United States Drug Allergy Registry (USDAR) grading scale \[grades NR for no reaction and then grades 0-4 with four being the most severe reaction\] and National Cancer Institute's Common Terminology Criteria for Adverse Events \[grades 1 to 5, with grades 1 being the mildest and grade 5 being death\]) in cephalosporin skin tests and drug challenges will be determined.

Sex: All, ages: 18 Years to 70 Years

Inclusion Criteria:

1. Age 18-70 years old.
2. Reaction history consistent with a potential immediate hypersensitivity reaction (pruritus, urticaria, erythema, angioedema, bronchospasm, wheezing, shortness of breath, anaphylaxis, or hypotension) to cefazolin, ceftazidime, ceftriaxone, cefepime, cephalexin, cefaclor, cefadroxil, cefuroxime, cefpodoxime, cefdinir, or cefixime.
3. English speaking or non-English speaking with translation services available.

Exclusion Criteria:

1. Severe concomitant medical condition (e.g., unstable coronary artery disease, congestive heart failure, severe chronic obstructive pulmonary disease, poorly controlled asthma, chronic renal failure, cirrhosis, or end-stage liver disease.)
2. History of Clostridioides difficile infection
3. Chronic spontaneous urticaria or systemic mastocytosis
4. Incident reaction required cardiopulmonary resuscitation
5. Reaction to 2 or more cephalosporin antibiotics
6. Active infection or antibiotic treatment within 7 days
7. Treatment with systemic antihistamines or corticosteroids within 7 days
8. Treatment with omalizumab or dupilumab within 60 days
9. Significant immunosuppression
10. Treatment with a beta-blocker or ACE inhibitor within 7 days
11. Use of investigational drugs within 60 days of participation
12. Anaphylaxis in the last 30 days
13. Penicillin anaphylaxis within the past year confirmed with positive penicillin skin tests
14. Prison or jail inmates, pregnant women, severe cognitive impairment
15. Current, diagnosed, mental illness or current, diagnosed, or self-reported drug or alcohol abuse that, in the opinion of the investigator, would interfere with the participant's ability to comply with study requirements
16. Past or current medical problems or findings from physical examination or laboratory testing that are not listed above, which, in the opinion of the investigator, may pose additional risks from participation in the study, may interfere with the participant's ability to comply with study requirements or that may impact the quality or interpretation of the data obtained from the study.
17. Inability or unwillingness of a participant to give written informed consent or comply with study protocol

• Kimberly G Blumenthal, MD, MSc, Principal investigator, Mayo Clinic
• David A Khan, MD, Principal investigator, University of Texas Southwestern Medical Center

NIH grants: U01AI184071