demonstrated.
“Prompt identification and discontinuation of a culprit drug is critical to improving patient outcomes and preventing recurrence,” researchers led by Sherrie J. Divito, MD, PhD, of the department of dermatology at Brigham and Women’s Hospital, Boston, wrote in the study, which was published online in JAMA Dermatology. “Identification is difficult because there is no laboratory test or other criterion standard (in the absence of rechallenge) to identify a culprit drug, and patients take on average six medications at the time of their reaction. Consequently, many patients may be labeled as allergic to multiple agents.”
Although failing to identify the culprit drug can have severe consequences, they added, “overlabeling” (labeling a patient as allergic to a drug or drugs that they can tolerate safely) “is not insignificant.” As a result of overlabeling, “the patient may receive a less efficacious, more toxic, and/or more expensive agent than necessary, and in some cases may be left without treatment for their underlying disease.”
To evaluate the outcomes of patients’ allergy lists, current approaches to identify culprit drugs such as the Algorithm for Drug Causality for Epidermal Necrolysis (ALDEN), which was published in 2010, and potential methods of improving culprit drug identification, the researchers performed a retrospective cohort study of 48 patients at Brigham and Women’s Hospital and Massachusetts General Hospital, with clinically and histologically confirmed cases of SJS/TEN between January 2000 and July 2018. Of the 48 patients, 26 had SJS/TEN overlap and 22 had TEN. Their median age at diagnosis was 40 years; 60.4% were female; and 52.1% were white, 12.5% were Black, 10.4% were Hispanic, and 8.3% were Asian. They took a median of 6.5 drugs in the 3 months prior to disease onset.
The researchers observed that all patients had at least one drug labeled as an allergy. A single culprit drug was labeled in 17 cases, but physicians communicated certainty in only 7 of those cases. Among all 48 patients, 104 drugs were labeled as allergies.
To identify a culprit drug, physicians appeared to mainly rely on two factors: drug notoriety and timing of exposure, compared with the onset of SJS/TEN. “Identifying high-risk medications seemed heuristic, with one or more drugs in question noted in the record as a common culprit without reference to published or vetted data regarding risk,” the researchers wrote. “Regarding timing, drug charts when present in medical records were incomplete, as they focused predominantly on high-notoriety drugs.”
In other findings, ALDEN scoring was discordant with physician-labeled lists in 28 cases. It labeled an additional 9 drugs missed by physicians and scored 43 drugs labeled as allergens by physicians as “unlikely.” The researchers also reported that 20 cases could have potentially benefited from human leukocyte antigen testing.
Their results “underscore the need for a laboratory test to identify culprit drugs,” but without such a test, “a systematic unbiased approach, such as ALDEN or the RegiSCAR database, with possibly HLA testing, should be considered to ensure the true culprit drug is not missed and exonerate as many nonculprit drugs as possible,” Dr. Divito and colleagues concluded.
They acknowledged certain limitations of the analysis, including its retrospective design and that many cases predated research advances in the topic area that took place during the 18-year study period.
Karl Saardi, MD, director of the inpatient dermatology service at George Washington University Hospital, Washington, who was asked to comment on the study, said that the findings “are consistent with clinical practice in that drug causality is usually determined by ‘gestalt’ rather than objective tools like the ALDEN algorithm.”
“The main limitation is the small size, which suggests the study sites are low-volume centers for SJS/TEN. The fact that the ALDEN score wasn’t developed until 2010 means that all the cases included prior to 2010 would not have applied the ALDEN algorithm, so I think the metric about how infrequently ALDEN was applied is not very meaningful.”
Still, he said that he was “surprised” by the number of medications that were added as allergies based on clinical impression, “and I’m glad this article does cast some light on the issue. In my experience, beta-lactam antibiotics are often – incorrectly – deemed to be the cause of SJS/TEN when further review of the patient’s medication history clearly shows they have tolerated these drugs multiple times in the past.”
Since 2000, he added, “our understanding of SJS/TEN has grown substantially including the identification of MIRM [mycoplasma-induced rash and mucositis]/RIME [reactive infections mucocutaneous eruptions] and GBFDE [generalized bullous fixed drug eruption] as mimickers.”
Christine Ko, MD, professor of dermatology and pathology at Yale University, New Haven, Conn., who was also asked to comment on the study, agreed that a limitation of the study is that it partially preceded development of the unbiased approaches to determining the cause of a medication reaction, such as the ALDEN system. “A strength of this study is the examination of heuristics in dermatology and how they relate to patient safety,” she added.
The study was funded by grants from the National Institutes of Health, a Dermatology Foundation Diversity Research Supplement Award, and by the German Research Foundation. Dr. Divito reported receiving personal fees from Adaptimmune and MEI Pharma and a provisional patent issued from Brigham and Women’s Hospital outside the submitted work. Neither Dr. Saardi nor Dr. Ko reported having relevant disclosures.