title: High proteinuria selectivity index based upon IgM is a strong predictor of poor renal survival in glomerular diseases.
abstract: BACKGROUND
  The transport of large proteins across the glomerular capillary wall (GCW) may increase several fold in glomerular diseases. The occurrence of IgM in urine is a consequence of the presence of large defects or shunts in the GCW, whereas albuminuria is probably a result of an altered charge- and size-selectivity of the GCW. In order to examine whether patho-morphological differences influence the renal outcome in proteinuric glomerulopathies, we examined urinary excretion of IgM and albumin as prognostic markers of glomerular disease.
  
  
  METHODS
  An observational study over a median of 41 (+/-3) months was conducted in 84 patients with biopsy-verified glomerular disease. The patients were subdivided into groups with low (< or =0.002) and high (>0.002) proteinuria selectivity index based upon IgM (IgM-SI), and into groups with low (< or =200 mg/mmol) and high (>200 mg/mmol) albumin creatinine index (ACI).
  
  
  RESULTS
  In the high IgM-SI group, the median creatinine clearance (Ccr) decreased by 26%, and 62% of the patients decreased in Ccr by >5 ml/ min/year during the follow-up time. In comparison, the median Ccr decreased by 8% in the low IgM-SI group (P<0.001) and only 18% of the patients in this group deteriorated by >5 ml/min/year in the Ccr. Eleven (21%) of the 51 patients in the high IgM-SI group developed end-stage renal failure compared with none of the 33 patients in the low IgM-SI group. All the patients that progressed to uraemia had decreased Ccr (<60 ml/min) at entry into the study. However, among all these patients, only those with high IgM-SI, and none with low IgM-SI, developed end stage renal failure. The fall in Ccr did not differ significantly between the patients in high (12%) and low (16%) ACI groups.
  
  
  CONCLUSIONS
  The results of this study indicate that an increased IgM-SI value is a stronger predictor of clinical outcome in proteinuric glomerulopathies than baseline albuminuria. This finding may reflect different patho-histological mechanisms influencing renal survival in glomerular diseases.
authors: Department of Nephrology, Lund University Hospital, Lund, Sweden.
authors: O
authors: O
authors: Bakoush
authors: O
authors: O
authors: Torffvit
authors: B
authors: B
authors: Rippe
authors: J
authors: J
authors: Tencer
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003404:Creatinine / Q000097:blood / Q000652:urine; D018450:Disease Progression; D005260:Female; D005921:Glomerulonephritis / Q000145:classification / Q000503:physiopathology / Q000652:urine*; D006801:Humans; D007075:Immunoglobulin M / Q000652:urine*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011379:Prognosis; D011507:Proteinuria; D016896:Treatment Outcome; D014511:Uremia / Q000503:physiopathology
chemical_list: D007075:Immunoglobulin M; D003404:Creatinine