Candidate Variables

The candidate predictors including demographic variables, clinical variables, and health care utilizations, and were selected based on the literature review and the knowledge of clinical experts.¹⁰ Clinical variables and health care utilizations were assessed by searching claims records within 1 year before the index date. Comorbid conditions, assessed using the diagnosis codes of the International Classification of Diseases, Ninth Revision, Clinical Modification (supplementary Table A1) were considered to be present if the diagnosis codes were recorded on ≥1 inpatient claim or ≥3 outpatient claims (variables are listed in Table ​Table11).²⁰ Medication prescribed to patients, such as antihypertensive drug, antidiabetic drugs, nonsteroidal anti-inflammatory drugs, antidepressant, anxiolytics, hypnotics, and antipsychotics, were analyzed, but there were no significant effect (data not shown). They are not included in prediction model at final.

Baseline Characteristics of Inpatient and Outpatient Cohorts, 2008