Patch Testing in Drug Eruptions: Practical Aspects and Literature Review of Eruptions and Culprit Drugs

ABSTRACT

There is overwhelming evidence that many delayed cutaneous adverse drug reactions (beginning >6 hours after drug intake) are mediated by delayed-type (type IV) hypersensitivity, including maculopapular eruptions, erythroderma, symmetrical drug-related intertriginous and flexural exanthema/baboon syndrome, eczematous eruptions, fixed drug eruptions, acute generalized exanthematous pustulosis, and drug reaction with eosinophilia and systemic symptoms/drug-induced hypersensitivity syndrome. Therefore, after resolution of the reaction, patch tests should be performed as first diagnostic method to identify the culprit drug(s). This article provides tools to perform drug patch tests properly and safely, discussing clinical history, indications, procedure, drug patch test materials, sensitivity, the meaning of negative patch tests, and safety of the procedure. In addition, a literature review of eruptions and culprit drugs is provided in tabular format.

Pharmaceutical Preparations for Intradermal Drug Tests

Our department of pharmacy takes over all the medical skin tests prescribed by the allergy department. The production takes place in specific premises, with qualified and calibrated equipment, by a qualified and regularly assessed staff—in compliance with the French preparation guidelines. The whole activity is under the responsibility of a pharmacist—handlings are performed by hospital pharmacy technicians. Each new intradermal skin test demand leads to a feasibility analysis—irritating nature, dilution solvent, concentration—this information is gathered in a thesaurus. The manufacturing steps are the following: prescription validation, production sheet and label printing, preparation of the needed equipment, batch numbers and expiration date checking, handling under a vertical laminar flow hood and control after production. The preparation activity increases continuously and the thesaurus currently contents 302 rows with following information: drug, dilution and reconstitution solvent, pure solution concentration and maximum concentration to test with intradermal tests. Work would prospect in costs reduction and resources optimization. Thanks to the allergists’ confidence, the partnership between the two departments can go on. This guarantees the quality of the preparations tested on patients but also the skin tests reproducibility.

A patch testing and cross-sensitivity study of carbamazepine-induced severe cutaneous adverse drug reactions

BACKGROUND

The usefulness of the drug patch testing for Stevens-Johnson syndrome and toxic epidermal necrolysis (SJS/TEN) is still controversial. Recent studies have shown that HLA-B*1502 is strongly associated with CBZ-SJS/TEN in Chinese and Southeast Asian populations.

OBJECTIVE

To evaluate the usefulness of patch tests for patients with carbamazepine (CBZ)-induced SJS, TEN and drug reaction with eosinophilia and systemic symptoms (DRESS) and the cross-reactivity in patch tests among the aromatic antiepileptic drugs.

METHODS

We measure the frequency of positive patch test reactions and cross-sensitivity to structure-related aromatic anti-epileptic drugs (AEDs) for patients after SJS/TEN or DRESS episodes caused by CBZ. CBZ and other structure-related AEDs used for patch testing were prepared in 10% and 30% petrolatum. Secondary measures included the association of HLA-B*1502 genotype and frequency of possible side effects from the patch tests.

RESULTS

Positive patch test reactions to 30% CBZ in the CBZ-SJS/TEN were 62.5% (10/16), and 70% (7/10) in the CBZ-DRESS. None of the 10 healthy controls displayed a positive reaction to tested agents. Cross-sensitivity to other aromatic AEDs was observed in both the CBZ-SJS/TEN and the CBZ-DRESS. Only the HLA-B*1502 genotype was present and strongly associated with the CBZ-SJS/TEN, but not with the CBZ-DRESS.

CONCLUSION

Drug patch testing is a safe and useful method for the identification of CBZ as the culprit drug of SJS/TEN as well as DRESS. Testing of chemically or pharmacologically related AEDs may provide information on cross-reactivity for these patients.

[Severe drug hypersensitivity reaction (DRESS syndrome) to doxycycline]

BACKGROUND

While many cases of DRESS reaction to minocycline have been described, few of these involve doxycycline.

CASE STUDY

A 59-year-old woman of African origin was repatriated after a journey to Ghana for hyperthermia with infiltrated maculopapular exanthema, facial oedema (no mucosal involvement) and polyadenopathy. Laboratory tests revealed hypereosinophilia, hepatic cytolysis and mononucleosis syndrome. Cutaneous histology was non-specific. The patient had been taking doxycycline as antimalarial prophylaxis for three weeks before the onset of symptoms. DRESS to doxycycline was diagnosed. Patch-tests with doxycycline three months later proved negative. The patient's HLA phenotype was A3/A30 and B39/B42.

DISCUSSION

An intrinsic causal relationship with doxycycline was likely in this case (I3). Although patch-test sensitivity and specificity with doxycycline remains unknown in DRESS exploration, a negative result does not necessarily rule out the diagnosis. A number of cases of DRESS to doxycycline have been described recently, possibly as a result of more frequent prescription (malarial prophylaxis, acne). Subjects of African ethnicity or having specific HLA phenotypes are at higher risk of developing drug hypersensitivity.

CONCLUSION

This patient is the third case of DRESS to doxycycline described in the literature. The originality of this case lies in the allergological investigation using patch-tests and HLA determination.

[Drug patch tests in the investigation of cutaneous adverse drug reactions]

Cutaneous adverse drug reactions (CADR) are a frequent problem in clinical medicine. Since patients are often on multiple drug regimes, it is often difficult to pinpoint the relevant drug from history alone. Besides clinical and chronological parameters, patch testing with the suspected compound has been reported as helpful in determining the cause of a CADR and in studying the physiopathological mechanisms involved in such reactions. The key advantage of drug patch tests is that they can be performed using any commercialized form of drugs and without hospital surveillance because they only rarely induce adverse reactions, which in any event are mild. The method for performing drug patch tests has been described, and requisite commercialized material is now commercially available, failing which the best approach is to dilute the drug in its commercialized form at 30% in petrolatum or in water. The results of drug patch tests depend on the drug tested and the clinical features of the initial CADR. They appear to be of value in investigating maculopapular rash, eczema at drug injection sites, photosensitivity (photopatch tests with 5J of irradiation), fixed drug eruption (testing at the sequelae site), acute generalized exanthematous pustulosis and symmetrical drug-related intertriginous flexural exanthema. Although less widely used, they are probably also of value in drug reaction with eosinophilia and systemic symptoms (DRESS) but they are of less use in Stevens-Johnson syndrome (SSJ) and Lyell's syndrome. Many drugs have been reported as producing positive patch tests, and most of these are summarized in a summary table of this literature review.

Negative predictive value of drug skin tests in investigating cutaneous adverse drug reactions

BACKGROUND

Drug skin tests are useful in aetiological analyses of cutaneous adverse drug reactions to determine if the drug can be rechallenged, or to avoid a cross-reaction with a substitute drug.

OBJECTIVES

To evaluate the negative predictive value of drug skin tests.

METHODS

We retrospectively analysed the files of patients referred for drug reactions. We have enrolled those having strictly determined drug reactions with clinical features, delayed onset after drug intake, drug causality assessment, and negative drug skin tests followed by drug administration. Oral provocation tests or substitution tests with a drug of the same class as that suspected of causing the drug reactions were performed.

RESULTS

From 1957 files analysed, 200 patients were included. After 403 patch tests, 403 prick tests and 304 intradermal tests, which were all negative, 260 oral provocation tests and 143 substitution tests were done; 307 different drugs were rechallenged. There were 42 positive drug re-administrations in 27 oral provocation tests and 15 substitution tests. The negative predictive value of our drug skin tests was 89.6%. The negative predictive value for beta-lactams was 87% for oral provocation tests and 96% for substitution tests, and for corticosteroids it was 100% and 74%, respectively.

CONCLUSIONS

Negative drug skin tests do not eliminate the responsibility of a drug in drug reactions, and must be followed by drug re-administration under hospital surveillance.