The Oxford classification of IgA nephropathy: pathology definitions, correlations, and reproducibility.
Pathological classifications in current use for the assessment of glomerular disease have been typically opinion-based and built on the expert assumptions of renal pathologists about lesions historically thought to be relevant to prognosis. Here we develop a unique approach for the pathological classification of a glomerular disease, IgA nephropathy, in which renal pathologists first undertook extensive iterative work to define pathologic variables with acceptable inter-observer reproducibility. Where groups of such features closely correlated, variables were further selected on the basis of least susceptibility to sampling error and ease of scoring in routine practice. This process identified six pathologic variables that could then be used to interrogate prognostic significance independent of the clinical data in IgA nephropathy (described in the accompanying article). These variables were (1) mesangial cellularity score; percentage of glomeruli showing (2) segmental sclerosis, (3) endocapillary hypercellularity, or (4) cellular/fibrocellular crescents; (5) percentage of interstitial fibrosis/tubular atrophy; and finally (6) arteriosclerosis score. Results for interobserver reproducibility of individual pathological features are likely applicable to other glomerulonephritides, but it is not known if the correlations between variables depend on the specific type of glomerular pathobiology. Variables identified in this study withstood rigorous pathology review and statistical testing and we recommend that they become a necessary part of pathology reports for IgA nephropathy. Our methodology, translating a strong evidence-based dataset into a working format, is a model for developing classifications of other types of renal disease.
Department of Cellular Pathology, John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK. ian.roberts@orh.nhs.uk
Roberts
Ian S D
IS
Cook
H Terence
HT
Troyanov
Stéphan
S
Alpers
Charles E
CE
Amore
Alessandro
A
Barratt
Jonathan
J
Berthoux
Francois
F
Bonsib
Stephen
S
Bruijn
Jan A
JA
Cattran
Daniel C
DC
Coppo
Rosanna
R
D'Agati
Vivette
V
D'Amico
Giuseppe
G
Emancipator
Steven
S
Emma
Francesco
F
Feehally
John
J
Ferrario
Franco
F
Fervenza
Fernando C
FC
Florquin
Sandrine
S
Fogo
Agnes
A
Geddes
Colin C
CC
Groene
Hermann-Josef
HJ
Haas
Mark
M
Herzenberg
Andrew M
AM
Hill
Prue A
PA
Hogg
Ronald J
RJ
Hsu
Stephen I
SI
Jennette
J Charles
JC
Joh
Kensuke
K
Julian
Bruce A
BA
Kawamura
Tetsuya
T
Lai
Fernand M
FM
Li
Lei-Shi
LS
Li
Philip K T
PK
Liu
Zhi-Hong
ZH
Mackinnon
Bruce
B
Mezzano
Sergio
S
Schena
F Paolo
FP
Tomino
Yasuhiko
Y
Walker
Patrick D
PD
Wang
Haiyan
H
Weening
Jan J
JJ
Yoshikawa
Nori
N
Zhang
Hong
H
D001706:Biopsy; D005922:Glomerulonephritis, IGA / Q000145:classification* / Q000473:pathology*; D006801:Humans; D007668:Kidney / Q000473:pathology*; D050527:Mesangial Cells / Q000473:pathology; D009336:Necrosis; D015203:Reproducibility of Results