Good interobserver and intraobserver agreement in the evaluation of the new ILAE classification of focal cortical dysplasias.
OBJECTIVE
An International League Against Epilepsy (ILAE) consensus classification system for focal cortical dysplasias (FCDs) has been published in 2011 specifying clinicopathologic FCD variants. The aim of the present work was to microscopically assess interobserver agreement and intraobserver reproducibility for FCD categories among an international group of neuropathologists with different levels of experience and access to epilepsy surgery tissue.


METHODS
Surgical FCD specimens covering a broad histopathology spectrum were retrieved from 22 patients with epilepsy. Three surgical nonepilepsy specimens served as controls. A total of 188 slides with routine or immunohistochemical stainings were digitalized with a slide scanner to allow Internet-based microscopy review. Nine experienced neuropathologists were invited to review these cases twice at a time gap of 3 months and different orders of case presentation. The 2011 ILAE FCD consensus classification served as instruction. Kappa analysis was calculated to estimate interobserver and intraobserver agreement levels. In a third evaluation round, 21 additional neuropathologists with different experience and access to epilepsy surgery reviewed the same case series.


RESULTS
Interobserver agreement was good (κ = 0.6360), with 84% consensus of diagnoses during the first evaluation (21 of 25 cases). Kappa values increased to 0.6532 after reevaluation, and consensus was obtained in 24 (96%) of 25 cases. Overall intraobserver reproducibility was also good (κ = 0.7824, ranging from 0.4991 to 1.000). Fewest changes in the classification were made in the FCD type II group (2.2% of 225 original diagnoses), whereas the majority of changes occurred in FCD type III (13.7% of 225 original diagnoses). In the third evaluation round, interobserver agreement was reflected by the level of experience of each neuropathologist, with κ values ranging from moderate (0.5056; high level of experience >40 cases/year) to low (0.3265; low level of experience <10 cases/year).


CONCLUSIONS
Our study achieved a good and reliable interobserver agreement among the group of expert neuropathologists originally involved in the ILAE FCD consensus classification system. Intraobserver reproducibility in this group was even more robust. These results showed considerable improvement compared to a previous study evaluating the 2004 Palmini FCD classification. Agreement levels were lower in our second group of neuropathologists and were related to their level of access and experience with epilepsy surgery specimens. These results suggested that the more precise ILAE definition of FCD histopathology patterns improves operational procedures in the diagnosis of FCDs. On the other hand, microscopic assessment of FCD is a challenge and requires sustained experience and teaching. The virtual slide review system allowed testing of this hypothesis and reached a widespread group of participating colleagues from different centers all over the world. We propose to further use this tool as a teaching device and also to address other epilepsy-associated entities still difficult to classify such as hippocampal sclerosis, long-term epilepsy-associated tumors, or mild malformations of cortical development (mMCDs), which were not yet covered by current ILAE classification systems.
Department of Neuropathology, University Hospital Erlangen, Erlangen, Germany. roland.coras@uk-erlangen.de
Roland
R
Coras
Onno J
OJ
de Boer
Dawna
D
Armstrong
Albert
A
Becker
Thomas S
TS
Jacques
Hajime
H
Miyata
Maria
M
Thom
Harry V
HV
Vinters
Roberto
R
Spreafico
Buge
B
Oz
Gianluca
G
Marucci
Jose
J
Pimentel
Angelika
A
Mühlebner
Josef
J
Zamecnik
Anna Maria
AM
Buccoliero
Fabio
F
Rogerio
Nathalie
N
Streichenberger
Nobutaka
N
Arai
Marianna
M
Bugiani
Silke
S
Vogelgesang
Rob
R
Macaulay
Carolin
C
Salon
Volkmar
V
Hans
Marc
M
Polivka
Felice
F
Giangaspero
Dyah
D
Fauziah
Jang-Hee
JH
Kim
Lei
L
Liu
Wang
W
Dandan
Jing
J
Gao
Benjamin
B
Lindeboom
Ingmar
I
Blümcke
Eleonora
E
Aronica
D002540:Cerebral Cortex / Q000473:pathology; D002648:Child; D002675:Child, Preschool; D004396:Coloring Agents; D004828:Epilepsies, Partial / Q000175:diagnosis / Q000473:pathology / Q000601:surgery; D005260:Female; D006801:Humans; D008297:Male; D054220:Malformations of Cortical Development / Q000145:classification* / Q000175:diagnosis / Q000473:pathology / Q000601:surgery; D015588:Observer Variation
D004396:Coloring Agents