Patch Testing for Evaluating Drug Reactions Due to Systemic Antibiotics

Skin testing as a biomarker in drug allergy

Despite the significant negative impact drug allergies can have on patient care, the diagnosis is largely based on clinical history, and there are limited diagnostic tests that can be done at the time of a reaction. Biomarkers are needed to improve the diagnosis and the identification of the culprit medication. Skin testing is the most useful biomarker for immediate- and delayed-type reactions available, but it is limited by its low sensitivity. To improve its accuracy and reproducibility, a standardized procedure must be used. For immediate-type reactions, penicillin skin testing is the most widely studied, and it can be used in patients with history of anaphylaxis or recent immunoglobulin E-mediated reaction or for whom there is a significant risk if a reaction were to occur, such as pregnancy. Skin testing is also important in allergy to platinum agents allowing for continued first-line therapy. For delayed-type reactions, patch testing and delayed intradermal testing, used in conjunction with clinical history, can help to improve identification of the culprit medication depending on the type of reaction. Other biomarkers including in vitro testing for specific immunoglobulin E, basophil activation test, lymphocyte transformation test, ELISpot, and genetic factors that increase the likelihood of reaction are under investigation, and they may be most helpful when used in combination with the clinical history and skin testing results.

The Role of Patch Testing in Evaluating Delayed Hypersensitivity Reactions to Medications

Confirming drug imputability is an important step in the management of cutaneous adverse drug reactions (CADR). Re-challenge is inconvenient and in many cases life threatening. We review the literature on ideal patch testing technique for specific CADRs. Testing should be performed approximately 3 months after the resolution of the eruption using standard patch testing techniques. Commercially available patch test preparations are available for a minority of drugs, so in most cases, testing should be performed with the drug at various recommended concentrations and in different vehicles. Testing to all known excipients, such as dyes, vehicles and preservatives is also important. Immunosuppressive medications should be discontinued or down titrated to the lowest tolerable dose to decrease the risk of false negative reactions. We provide an overview of expert recommendations and extant evidence on the utility of patch testing for identifying the culprit drug in common CADRs and for specific drug or drug classes. Overall, there appears to be significant variability in the patch test positivity of different drugs, which is likely the result of factors intrinsic to the drug such as dermal absorption (as a function of lipophilicity and molecular size) and whether the drug itself or a downstream metabolite is implicated in the immune reaction. Drugs with high patch test positivity rates include beta-lactam antibiotics, aromatic anticonvulsants, phenytoin, and corticosteroids, among others. Patch testing positivity varies both as a function of the drug and type of CADR. The sum of the evidence suggests that patch testing in the setting of morbilliform eruptions, fixed drug eruption, acute generalized exanthematous pustulosis, and possibly also drug-induced hypersensitivity syndrome, photoallergic and eczematous reactions may be worthwhile, although utility of testing may vary on the specific drug in question for the eruption. It appears to be of limited utility and is not recommended in the setting of other complex CADR, such as SJS/TEN and leukocytoclastic vasculitis.

A Case of Amoxicillin-Induced Acute Generalized Exanthematous Pustulosis Presenting as Septic Shock

This case report demonstrates the challenges of diagnosing and managing acute generalized exanthematous pustulosis (AGEP) presenting as septic shock. The disseminated, erythematous, pustular rash is a common feature. However, extensive organ involvement and life-threatening hypotension are unusual. The constellation of signs has not previously been documented following amoxicillin therapy. Toxic epidermal necrolysis (TEN) and toxic shock syndrome (TSS) were considered in addition to AGEP because of the systemic presentation. AGEP was diagnosed following histopathology (TEN was ruled out based on limited necrotic keratinocytes and lack of epidermal necrosis) and a negative antistreptolysin O titer (eliminated TSS). Antibiotic therapy for septic shock was provided before the diagnosis was confirmed as AGEP. Upon confirmation of the AGEP diagnosis, antibiotics were discontinued and a 5-day course of oral prednisone (40 mg/d) was initiated in addition to topical half-strength (0.05%) betamethasone valerate. The patient rapidly improved and was discharged. Outpatient patch testing confirmed amoxicillin as the culprit drug. In conclusion, it is critical to realize that AGEP cannot be ruled out with a septic shock presentation. Recent drug history is critical in recognizing an adverse drug reaction, and patch testing is useful for determining the culpable drug when the diagnosis is AGEP.

Long-term reproducibility of positive patch test reactions in patients with non-immediate cutaneous adverse drug reactions to antibiotics

BACKGROUND

As in contact allergy, T cell-mediated hypersensitivity in non-immediate (NI) cutaneous adverse drug reactions (CADRs) to antibiotics is considered to be lifelong, but, in this setting, patch tests have rarely been repeated after long time intervals.

OBJECTIVE

To evaluate the long-term reproducibility of positive patch test reactions to antibiotics in patients with NI CADRs.

METHODS

Fifty-six patients with NI CADRs to antibiotics who had relevant positive reactions during patch testing were invited to repeat patch tests with a similar antibiotic series 2-15 years thereafter.

RESULTS

Twenty patients were included (9 males and 11 females; mean age 54.6 years): 18 with maculopapular exanthema, 1 with drug hypersensitivity syndrome, and 1 with acute generalized exanthematous pustulosis. Results were reproducible in 17 of 20 patients after a mean interval of 6.0 years (range 2-14.7 years). Concerning β-lactams, 7 of 8 patients remained positive for aminopenicillins, 4 of 4 for isoxazolyl penicillins, and 1 for cefoxitin. Patch test results were also reproducible for clindamycin in 5 of 7 patients, for vancomycin in 1 patient, and for spiramycin in 1 patient. Reproducibility was not affected by the time interval between tests, sex, or age at testing.

CONCLUSIONS

In the context of NI CADRs, we showed high reproducibility of positive patch test reactions to various antibiotics, even after several years.

Patch testing - a valuable tool for investigating non-immediate cutaneous adverse drug reactions to antibiotics

BACKGROUND

Antibiotics are among the most frequent causes of cutaneous adverse drug reactions (CADR); patch testing may be an important tool in their evaluation and management. We assessed the role of patch testing as a diagnostic tool in non-immediate CADR to antibiotics, and evaluated cross-reactivity among them.

METHODS

We reviewed data from all patients with non-immediate CADR attributed to antibiotics, which were patch tested between 2000 and 2014 at our dermatology department.

RESULTS

Patch tests were performed in 260 patients, and showed overall reactivity to antibiotics of 21.5%, especially in the context of drug reactions with eosinophilia and systemic symptoms (DRESS) (31.6%), maculopapular exanthema (MPE) (21.8%), Stevens-Johnson syndrome/toxic epidermal necrolysis (20%) and acute generalized exanthematous pustulosis (AGEP) (18.1%). Patch test reactivity was higher for amoxicillin, mainly in DRESS (44.4%) and MPE (25.6%), and dicloxacillin (50% in AGEP and 37.5% in MPE). Reactivity to clindamycin occurred, especially in the setting of MPE (23.2%). In AGEP and DRESS, patch tests were useful in detecting reactivity to quinolones (50-100%). Overall reactivity was lower for vancomycin (9.1%), co-trimoxazole (8.6%), macrolides (4.8%) and cephalosporins (4.4%). Positive patch tests for more than one antibiotic occurred in 29/56 cases (51.8%), mostly explained by cross-reactions. Twenty of 24 cases reacted to both amoxicillin and ampicillin. All five cases reacting to ciprofloxacin cross-reacted with other quinolones.

CONCLUSION

Although oral rechallenge is considered the gold standard for confirming drug imputability in CADR, patch testing could be suggested as a first choice in the study of non-immediate reactions, since it is a safe and valuable procedure.

Contact dermatitis: a practice parameter-update 2015

This parameter was developed by the Joint Task Force on Practice Parameters, which represents the American Academy of Allergy, Asthma & Immunology (AAAAI); the American College of Allergy, Asthma & Immunology (ACAAI); and the Joint Council of Allergy, Asthma & Immunology. The AAAAI and the ACAAI have jointly accepted responsibility for establishing "Contact Dermatitis: A Practice Parameter-Update 2015." This is a complete and comprehensive document at the current time. The medical environment is changing and not all recommendations will be appropriate or applicable to all patients. Because this document incorporated the efforts of many participants, no single individual, including members serving on the Joint Task Force, are authorized to provide an official AAAAI or ACAAI interpretation of these practice parameters. Any request for information or interpretation of this practice parameter by the AAAAI or ACAAI should be directed to the Executive Offices of the AAAAI, the ACAAI, and the Joint Council of Allergy, Asthma & Immunology. These parameters are not designed for use by the pharmaceutical industry in drug development or promotion. Previously published practice parameters of the Joint Task Force on Practice Parameters for Allergy & Immunology are available at http://www.JCAAI.org or http://www.allergyparameters.org.