Patch tests in nonimmediate cutaneous adverse drug reactions: The importance of late readings on day 4

Patch tests in non-immediate cutaneous adverse drug reactions: Late readings on Day 4 is more sensitive than on Day 3

BACKGROUND

Patch tests (PTs) are recommended to identify the culprit drug in non-immediate cutaneous adverse drug reactions (NICADRs). We recently reported that, in patients with NICADRs, a unique reading of PTs at day (D)2 compared with an additional second late reading at D4 missed almost half (45.3%) of the positive PTs.

OBJECTIVES

To assess the change in sensitivity of the PT reading on D4 compared with the reading on D3.

METHODS

We performed a retrospective (July 2020-June 2023) monocentric study of patients who had PTs with two readings for a NICADR. We compared reading on D3 and the second reading on D4 for the suspected drug (primary outcome) and for the related drugs tested simultaneously (secondary outcome).

RESULTS

During the study period, 249 patients underwent patch testing with D3 and D4 readings. Regarding the primary outcome, the first reading at D3 was positive for 13.7% of patients, and the reading at D4 for 24.9% of patients (p < 0.0001). Regarding the secondary outcome, only 9.6% of patients had all their positive PT at D3 compared with 24.9% of patients at D4 (p < 0.0001). Considering the evaluated drug classes, no statistical difference was observed. However, we highlight that D3 reading detected all positive carbamazepine PTs (n = 3) while positive clindamycin PTs (n = 4) were identified only with the help of the second reading on D4.

CONCLUSION

This study showed that, an additional D4 reading compared with a single D3 reading enhanced the sensitivity of PTs to identify culprit drugs and related. Further studies should replicate these findings and evaluate the medico-economic balance and safety of a single reading of PTs on D4.

Skin Testing and Drug Provocation Tests in Epidermal Necrolysis: A French Experience

BACKGROUND

There are limited data on the use of skin testing, other than patch testing, and challenges in the evaluation of epidermal necrolysis (EN), including Stevens-Johnson syndrome and toxic epidermal necrolysis.

OBJECTIVE

To report a French multicenter experience in skin testing and challenges in EN, and investigate the factors associated with tests' positivity.

METHODS

All patients who were evaluated by patch tests (PTs), skin prick tests, intradermal tests (IDTs), or drug provocation tests (DPTs) for EN between 2010 and 2020 were retrospectively included through 2 French drug reaction networks.

RESULTS

In total, 113 patients were included from 8 centers. Median (interquartile range) time from EN to hypersensitivity workup was 7.9 months (5.1-15 months). All patients had PTs, 17 (15%) had skin prick tests or IDTs with delayed readings and 32 (28.3%) had DPTs. One mild reaction occurred after a DPT. Overall, 22 patients (19.5%) had positive PTs, and the only factors associated with positivity were Algorithm of Drug Causality for Epidermal Necrolysis (ALDEN) score and drug class. Only 1 IDT was positive but considered irrelevant. The DPTs were never performed to prove responsibility of a highly suspected drug but were used to confirm current tolerance of needed medications.

CONCLUSIONS

Allergological workup in EN, performed by specialists involved in EN, seems safe. Skin tests, although of limited sensitivity, can be helpful for considering the reintroduction of essential drugs according to a benefit-to-risk decision. We propose an algorithm for approaching hypersensitivity testing in patients with EN, to be adapted to each patient.

Hypersensitivity Reactions to Iodinated Contrast Media

At present, iodinated contrast media (ICM) are mostly non-ionic, have low osmolality, and are safe. Even if adverse drug reactions (ADRs) occur, most are chemo-toxic symptoms and require only observation or H1 antihistamines. However, rare, unpredictable, and even life-threatening hypersensitivity can still occur. The aim of this review is to summarize the issues that all relevant staff need to know about and be able to respond to. The most significant risk factor for ICM hypersensitivity is a history of ICM hypersensitivity. For high-risk populations, we must cautiously weigh the advantages and disadvantages of premedication and be aware that breakthrough reactions may still occur. The best policy for patients with a history of severe ICM hypersensitivity is to avoid the same ICM. If ICM are inevitable, skin tests, in vitro tests, and drug provocation tests may help to find a feasible alternative that is safer. The severity of the hypersensitivity is correlated with the positivity rate of these tests, so there is no need for further investigations for patients with only mild reactions. We should also keep in mind that even excipients in ICM may induce hypersensitivity. Detailed, standardized documentation is essential for correct diagnosis and the prevention of future occurrence.

Patch testing in Drug reaction with eosinophilia and systemic symptoms (DRESS): a literature review

The literature on positive patch test results in drug reaction with eosinophilia and systemic symptoms (DRESS) is reviewed. 105 drugs were identified that have together caused 536 positive patch tests in 437 patients suffering from DRESS. By far most reactions (n=145) were caused by carbamazepine, followed by amoxicillin, isoniazid, phenytoin, ethambutol, fluindione, phenobarbital, rifampicin, and ceftriaxone; 43 drugs each caused a single case only. The drug classes causing the highest number of reactions are anticonvulsants (39%), beta-lactam antibiotics (20%), antituberculosis agents (11%), non-beta-lactam antibiotics (6%) and iodinated contrast media (5%). The sensitivity of patch testing (percentage of positive reactions) is high for anticonvulsants (notably carbamazepine), beta-lactam antibiotics (notably amoxicillin) and possibly iodinated contrast media. Allopurinol and sulfasalazine frequently cause DRESS, but never give positive patch tests. Patch testing in DRESS appears to be safe, although mild recurrence of DRESS symptoms, mostly skin reactions, may not be rare. Multiple drug hypersensitivity was found to occur in 16% of all patients, but it is argued that the true frequency is (far) higher. Clinical aspects of DRESS, including diagnosing the disease and identifying culprit drugs (patch tests, intradermal tests, in vitro tests, challenge tests) are also provided, emphasizing the role of patch testing. This article is protected by copyright. All rights reserved.