Background There is a general consensus that elevated serum beta-2 microglobulin (B2M) levels measured at a single time-point are significantly associated with mortality in patients on maintenance dialysis. To date, the majority of prior studies that have examined B2M-associated mortality have been conducted in prevalent hemodialysis patients with little residual renal function (RRF). However, studies in incident peritoneal dialysis (PD) patients are lacking. Moreover, changes in serum B2M levels over time have not been considered in this population. Methods We examined the association of time-updated and baseline serum B2M levels with mortality in a 10-year cohort of 725 incident PD patients who were maintained on dialysis between January 2006 and December 2011 using Cox proportional hazards regression analyses. Patients were categorized into tertiles according to B2M levels. Results During a median follow-up of 38 (interquartile range 23-64) months, 258 (35.4%) deaths occurred, including 106 (14.6%) and 86 (11.9%) deaths from cardiovascular and infectious causes, respectively. The lowest B2M tertile was associated with a higher risk of all-cause and infectious mortality compared with the middle tertile: the hazard ratios (95% confidence interval) for all-cause deaths were 2.12 (1.38-3.26) and 2.20 (0.96-5.05) in time-varying analyses and 1.52 (1.07-2.17) and 2.41 (1.19-4.88) in baseline analyses. Subgroup analyses showed that this association was particularly observed in females, older patients, those with comorbidities such as diabetes, a lower body mass index, lower albumin levels or those with higher RRF (all P for interactions <0.05). Conclusions In incident PD patients, lower B2M levels were independently associated with overall and infectious mortality. These associations can be potentially modified by malnutrition, inflammation and RRF.
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