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Frequent lab testing is common, but low-yield, for isotretinoin patients



Abnormalities in lipids, liver enzymes, and blood counts were rare, and serious abnormalities virtually nonexistent among individuals taking isotretinoin for moderate to severe acne who received laboratory testing.

In a review of 1,863 patients receiving isotretinoin, there were no cases of grade 4 abnormalities of lipids, liver enzymes, or complete blood count (CBC). Further, fewer than 1% of patients had grade 2-3 laboratory abnormalities, and no patients had cholesterol or CBC abnormalities of grade 3 or higher.

The retrospective cohort study used an electronic database to identify patients who were prescribed isotretinoin for acne from 2007 to 2017, with inclusion criteria structured to “increase the likelihood of capturing a complete course of isotretinoin therapy,” wrote John Barbieri, MD, and coauthors. The database allowed the investigators to group lab values into baseline testing, and testing by month of therapy for individual deidentified patient records.

Dr. Barbieri, a dermatologist and postdoctoral research fellow at the University of Pennsylvania, Philadelphia, and coinvestigators found that over half of all patients had baseline triglyceride, total cholesterol, AST, ALT, and platelet and white blood cell count levels.

Though the number of patients who had any of these levels checked in a given month of treatment declined over time, as did the total number of patients still on isotretinoin therapy, monthly AST and ALT monitoring occurred in 37.6%-58.5% of patients. Monthly triglyceride monitoring was conducted in between 39.6% and 61.4% of participants, and CBCs were obtained in 26.8%-37.4% of participants.

In terms of the abnormalities that were seen, grade 1 triglyceride elevations of 150-300 mg/dL were present in about 13% of patients at baseline, rising to 39% of participants who were still receiving isotretinoin at month 6. However, grade 2 elevations of up to 500 mg/dL were seen in 1.4% of patients at baseline and 2.4%-5.6% of patients during subsequent months.

Grade 1 liver enzyme abnormalities of less than three times the upper limit of normal values were seen at baseline in under 4% of patients, and in no more than 6.7% of patients through the course of treatment.

Leukopenia of between 3 x 103/mcL and the lower limit of normal occurred in 4.1% of baseline tests and in 6.6%-10.1% of tests in subsequent months. Grade 1 thrombocytopenia (values between 75 x 103/mcL and the lower limit of normal) occurred in 1.9% of baseline tests and no more than 2.9% of tests in the following months.

The results, wrote Dr. Barbieri and coauthors, affirm that most patients fare well on isotretinoin, and frequent laboratory testing is likely to be low-yield. Even using relatively low Medicare reimbursement rates for these tests yielded an estimated $134 in per-patient charges for the studied population. If baseline lipid and liver functions were followed only by repeat testing when peak isotretinoin dose was reached, charges would drop to about $87 per patient. Using the iPLEDGE database figures, this would save $17.4 million in monitoring costs annually, they wrote.

They also calculated that the monitoring regimen they observed puts the cost of detecting one single grade 3 hepatic enzyme elevation at $6,000; one grade 3 triglyceride elevation would cost $7,750.

Of the patients, 49% were female, the median age was 18.2 years, and the median duration of isotretinoin therapy was under 5 months (148 days). Nearly 90% of patients were white and non-Hispanic; 2.5% were black.

The data used for the analysis did not give the investigators access to clinician notes, but they did observe that, even when abnormal test values were seen, isotretinoin prescribing continued. This, they added, pointed toward reassuring clinical scenarios, even in cases of abnormal lab values.

“These findings are consistent with prior studies and suggest that extensive laboratory monitoring observed in this population may be of low value,” concluded Dr. Barbieri and colleagues. “In addition, changes to lipid levels observed in this study typically occurred during the first 2-3 months of therapy before stabilizing, which is consistent with findings in prior studies.”

The investigators noted that, despite mounting evidence of isotretinoin’s safety, there was no trend toward decreased CBC testing over the decade-long period of the study, and there were only “modest” decreases in hepatic enzyme and lipid monitoring. They called for an awareness campaign on the part of professional societies, and consideration for “more specific guideline recommendations” that may ease the testing burden on the adolescent and young adult population receiving isotretinoin.

The study was funded in part by the National Institutes of Health, and Dr. Barbieri receives partial salary support from Pfizer through a grant to the University of Pennsylvania. He has received support for unrelated work from Eli Lilly and Novartis. The other authors reported no conflicts of interest.

SOURCE: Barbieri J et al. J Am Acad Dermatol. 2020 Jan;82(1):72-9.

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