Urine IgM-excretion as a prognostic marker for progression of type 2 diabetic nephropathy

Although the clinical manifestations of type 2 diabetic nephropathy and decline in kidney function are similar to those in type 1, the clinical course and the renal structural changes are more heterogeneous in type 2 diabetic patients. Previous studies have shown that an increased urine IgM excretion in patients with type 1 diabetic nephropathy was associated with poor outcome. In the present follow-up study we examine the prognostic value of baseline urine IgM excretion in patients with type 2 diabetes mellitus. Methods: A cohort of 106 (74 male and 32 female) patients with type 2 diabetes regularly attending our diabetes out-patient clinic at Skane University Hospital in Lund. They were recruited prospectively under the period between 1992 and 2004. Patients were followed-up until January 2009. The end point was cardiovascular (CV) death or end-stage renal disease (ESRD). The median follow-up time was 5 years (0.5-13 years). Participants were divided according to degree of albuminuria and IgM-uria. Results: During follow-up time, 28 (19 male and 9 female) patients died of CV events and 41 (26 male and 15 female) developed ESRD. The risk of CV mortality was 2.4 fold, and the risk of renal failure 4.9 fold higher in patients with increased urine IgM excretion compared to patients with low urine IgM excretion. Stratified analysis showed that an increased urine IgM excretion was an independent predictor of renal and cardiovascular death irrespective of the degree of albuminuria (HR = 3.6, 95% CI: 2.1-6.0, P< 0.001).In conclusion, type 2 diabetic nephropathy patients with high urine IgM excretion rates carry an increased risk of renal and cardiovascular death.