TABLE 3.

Variable Importance of Year 1 Covariates Potentially Related to Any Flare-Related Inpatient or ED Visits in Year 2 Based on Classification and Regression Tree Model

Predictor	Variable importance
Opioids	1.000
Other neurological disordersa	0.964
Any ED visit	0.918
Any inpatient admission	0.892
Depression	0.643
Chronic kidney disease or renal failure	0.318
Any systemic corticosteroid	0.135
Lupus nephritis	0.099
Race	0.090
Hypertension	0.089
Pericarditis	0.027

The following characteristics were also included in the model but had a variable importance of 0.000: aged at least 45 years, aged at least 65 years, sex, insurance plan type, cancer, chronic pulmonary disease, coagulopathy, congestive heart failure, diabetes, drug abuse, liver disease, peripheral vascular disorders, anxiety, atherosclerosis, cerebrovascular disease/stroke/transient ischemic attack, endocarditis, myocardial infarction, fibromyalgia, fractures, kidney transplant, osteoarthritis, osteoporosis, pleurisy/pleural effusion, Raynaud disease, thrombocytopenia, antidepressants, and antihypertensives.

^a “Other” neurological disorders are defined in the Elixhauser Comorbidity Index as neurological conditions other than dementia, seizures and epilepsy, or neurological disorders affecting movement.

ED = emergency department.