Background Cutaneous involvement is one of the most frequent manifestations of systemic lupus erythematosus (SLE); however ethnicity may influence its prevalence and clinical expression.
Objectives We aimed to evaluate its prevalence and associated factors in a non-Caucasian population.
Methods Data from a cohort of 310 patients with SLE (ACR 1997 update) who were seen at a single clinical center were analyzed. The cutaneous involvement latent trait (CILT) was constructed using item response theory and two-parameter logistic model (1) which involved the following variables: photosensitivity, oral ulcers, malar rash, discoid lupus, subacute lupus and urticary. CILT was included as dependent variable in a lineal regression model, adjusted for gender and age at onset.
Results Cutaneous involvement was observed in 88% (n=273) of patients, and was associated with familial autoimmunity (β=0.44, p=0.001), renal involvement (β=0.34, p=0.042), serositis (β=0.32, p=0.009) and immunological criteria (β=0.20, p=0.035). On the other hand, inverse relationship with age at onset (β=-0.01, p=0.027) and leukopenia (β=-0.23, p=0.03) was found. Some interactions were also observed. Among these, patients with polyautoimmunity tended to have a lower CILT than those with lupus arthropathy.
Conclusions Cutaneous involvement is a common manifestation in our SLE population. Found associations and interactions can help distinguish patients at risk and guide early interventions. Latent trait analysis may be an instrumental tool for the study of subphenotypes in SLE and other autoimmune diseases.
Rizopoulos, D. (2006) ltm: An R package for latent variable modeling and item response theory analyses. Journal of Statistical Software, 17(5), 1–25.
Disclosure of Interest None Declared