title: The clinical relevance of a repeat biopsy in lupus nephritis flares.
abstract: BACKGROUND
  The clinical utility of performing repeat biopsies during lupus nephritis flares is questionable and data pointing towards frequent class switches are based on the old WHO classification. This retrospective study investigates the hypothesis that clinically relevant switches from proliferative to non-proliferative lesions and vice versa as determined by the new ISN/RPS classification are a rare event and that repeat biopsies are unnecessary in many cases.
  
  
  METHODS
  Thirty-five patients with lupus nephritis and one or more repeat renal biopsies were included. Eighty-four biopsies were blindly reassessed according to the ISN/RPS classification.
  
  
  RESULTS
  Twenty-five patients had one repeat biopsy, 6 patients had two and 4 patients had three repeat biopsies. Forty-nine comparisons between reference and repeat biopsies could be made. In 25 cases (54.3%), there was no shift in ISN/RPS class on repeat biopsies. In 41 instances, paired biopsies showed proliferative lesions both on reference and repeat biopsies, whereas five of six cases with non-proliferative lesions on a reference biopsy switched to proliferative lesions on a repeat biopsy. Clinically significant class switches during lupus nephritis flares were more frequent in patients with non-proliferative lesions in their reference biopsy (P < 0.001).
  
  
  CONCLUSIONS
  The results show that patients with proliferative lesions in the original biopsy rarely switch to a pure non-proliferative nephritis during a flare. Therefore, a repeat biopsy during a lupus nephritis flare is frequently not necessary if proliferative lesions were found in the reference biopsy. However, in the case of a non-proliferative lesion in the reference biopsy, class switches are frequently found and repeat biopsies are advisable.
authors.affiliation: Department of Nephrology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Gabriëlle M N
authors.initials: GM
authors.lastname: Daleboudt
authors.forename: Ingeborg M
authors.initials: IM
authors.lastname: Bajema
authors.forename: Natascha N T
authors.initials: NN
authors.lastname: Goemaere
authors.forename: Jaap M
authors.initials: JM
authors.lastname: van Laar
authors.forename: Jan A
authors.initials: JA
authors.lastname: Bruijn
authors.forename: Stefan P
authors.initials: SP
authors.lastname: Berger
mesh_terms: D000328:Adult; D001706:Biopsy / Q000009:adverse effects / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008181:Lupus Nephritis / Q000209:etiology / Q000473:pathology*; D008297:Male; D012189:Retrospective Studies