Measurements

We defined the first date of a series of regular dialysis treatments in OPD as the date of dialysis initiation. If an admission with a dialysis treatment code preceded this OPD event, the date of this admission was regarded as the initiation date. In the NHIRD, treatments and procedures during admission were not dated.

The critical care period was defined as the time within 6 months before initiation of dialysis [17], and the early care period was defined as the time 6 to 36 months before initiation of dialysis. Patients with any nephrology OPD visit during early care periods were defined as early referral patients (6 to 36 months before initiation of dialysis). And those without any nephrology OPD visit during early care periods were defined as late referral patients.

Kip KE et al did literature review and found that there was no consensus definition of major adverse cardiovascular events, usually abbreviated as MACE. Varying definitions of composite end points can lead to substantially different results and conclusions [20]. This study used the nomenclature of composite major cardiovascular events, which was consisted of all-cause mortality, acute myocardial infarction and stroke, to avoid confusion.

Patient demographics included age, gender, socioeconomic status (individual income), urbanization, initial dialysis modality, and disease severity. Disease severity was estimated with the Deyo adaptation of the Charlson Comorbidities Index Score (CCIS), which was derived from inpatient and outpatient diagnoses in the last six months of life [21]. CKD was excluded in calculation of the CCIS.