Study takes a closer look at the ISN/RPS classification scheme for lupus glomerulonephritis.


BOSTON—A widely used classification scheme for lupus glomerulonephritis (GN) may mask the pathologic and prognostic implications of focal segmental lupus GN, according to researchers.

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The criteria, developed by the International Society of Nephrology/Renal Pathology Society (ISN/RPS), may lump diffuse and focal segmental lupus GN into the category of diffuse lupus GN.


“This is the first study to take apart the classification of the ISN/RPS group and to look at it from the standpoint of segmental lesions,” said investigator Robert S. Katz, MD, associate professor of medicine at Rush University Medical College in Chicago. “These lesions are really significant clinically, and if patients have diffuse segmental lesions they do worse and they need to be treated more aggressively.”


The World Health Organization (WHO) class III (involving 50% or more glomeruli) or greater and WHO class IV are not congruent with classes IV-S and IV-G in the ISN/RPS classification scheme, Dr. Katz said. In addition, application of ISN/RPS criteria to biopsies with severe lupus GN may minimize pathological and outcome differences between patients with ISN/RPS classes IV-S and IV-G. He and his colleagues have concluded that this may result in the loss of informational content from the renal biopsies.


Nephrologists need to be aware that ISN/RPS criteria cannot be used to detect morphological or clinical differences among patients with severe lupus GN, said Dr. Katz, who presented study findings here at the American College of Rheumatology annual meeting.


He and his colleagues obtained 39 renal biopsies with diffuse global lupus GN (WHO class IV) and 44 renal biopsies with severe segmental GN (WHO class III) and reclassified them by using the ISN/RPS classification system. There were 22 biopsies with ISN/RPS class IV-S, 39 class IV-G, and 22 that switched from WHO class III to class IV-G. Class IV-G had significantly more immune aggregate deposition than classes IV-S and IV-Q. Patients with IV-G had lower serum complements C3 and C4 than patients with IV-Q (diffuse segmental lesions).


Patients with IV-G had more remissions (56%) than those with IV-Q (23%). Stable renal function at last follow-up was less frequent in patients with IV-Q (18%) than IV-S (50%) and IV-G (62%). The investigators found that renal survival and renal survival without end-stage renal disease were different when the patients were diagnosed as WHO III 50% or greater and WHO class IV. Outcomes for ISN/RPS class IV-S and the combined class of IV-G plus IV-Q did not differ, however. WHO class III 50% or greater and WHO class IV are not congruent with classes IV-S and IV-G in the ISN/RPS scheme.


“Nephrologists need to know about this because when they do kidney biopsies on their lupus patients and they see either focal segmental disease or diffuse segmental disease they need to treat those groups more aggressively,” Dr. Katz said.