Objective: To determine the incidence of abnormal laboratory test results among isotretinoin users.
Design: Retrospective cohort.
Setting: Comprehensive managed care health plan in Northern California.
Participants: The study population comprised 13 772 patients aged 13 to 50 years with acne, undergoing oral isotretinoin therapy between March 1995 and September 2002.
Main outcome measures: Laboratory values for serum triglyceride, total cholesterol, and liver transaminase levels; white blood cell count, hemoglobin level, and platelet count; and frequency of abnormal laboratory results by severity grade as defined by the National Cancer Institute Common Terminology Criteria for Adverse Events v3.0.
Results: Substantial increases in the cumulative incidence of abnormalities were seen in serum lipid and transaminase levels, but not in hematologic parameters, during isotretinoin treatment compared with the baseline period. The cumulative incidence of new abnormalities in patients with normal values at baseline was 44% for triglyceride level, 31% for total cholesterol level, and 11% for transaminase level. Moderate to severe abnormalities in lipid and transaminase levels were generally transient and reversible. New abnormalities in hematological test results were uncommon.
Conclusions: The incidence of abnormally high serum lipid levels during isotretinoin treatment may be greater than previously estimated. Elevations in transaminase level are generally mild. Normal baseline values of serum lipid and transaminase levels do not preclude the development of new abnormalities during isotretinoin treatment. Routine monitoring of white blood cell count, hemoglobin level, and platelet count during isotretinoin therapy may be of little utility without clinical suspicion of an abnormality. The clinical significance of laboratory abnormalities during isotretinoin therapy remains to be determined.