Background The Cutaneous Lupus Disease Activity and Severity Index (CLASI) is a responsive outcome instrument with high inter- and intra-rater reliability in patients with cutaneous lupus erythematosus (CLE). Recently, there has been discussion about the activity alopecia and mucous membrane components of the CLASI. Overlap of these elements with non-lupus etiologies poses the question if alopecia and mucous membrane signs are important to capture.

Methods In this retrospective study of our prospectively collected data, we examined whether the CLASI could capture a similar degree of clinical change with the removal of these components. 171 patients with alopecia and/or oral activity, two consecutive visits, and a CLASI activity (CLASI-A) ≥4 were selected for this study and grouped according to alopecia involvement. Percent change in CLASI-A scores before and after removal of alopecia and mucous membrane components were compared for each patient. Statistical analysis was performed using Paired Wilcoxon Signed Rank Test.

Results Following removal of these components, there was a -1.39% median difference (IQR 49.18, p=0.457) in CLASI-A percent change for patients with recent hair loss or mucous membrane lesions (n=34), -2.08% median difference (IQR 137.66, p=0.013) for patients with diffuse hair loss (n=26), and -11.76% median difference (IQR 42.13, p=0.002) for patients with focal/patchy alopecia in one or more quadrants (n=111). The percentage difference change was most significant for patients with focal/patchy alopecia compared to patients with diffuse alopecia and recent hair loss.

Conclusions Exclusion of alopecia and mucous membrane involvement from the CLASI-A score limits capturing valuable objective clinical information on disease activity. This is problem given that activity alopecia greatly impacts quality of life for patients with CLE. These components should be retained and continued to be scored, as supported by the extensive validation of the CLASI.