A two-phase study model for the standardization of HER2 immunohistochemical assay on invasive ductal carcinoma of the breast.
OBJECTIVE
To develop and verify a standardized protocol for HER2 immunohistochemical assays on invasive ductal carcinoma of the breast in Thailand.


METHODS
A two-phase study approach was employed. In the Phase One, after verifying the proposed protocol that adopted the HercepTest procedure using readily available primary antibodies, CB11 and A0485, Lab 1 performed the HER2 immunohistochemical staining for 137 cases of invasive ductal carcinoma twice with two types of the antibody. Nine pathologists from 8 centers independently examined and scored all the 2 x 137 stained slides that were blinded for antibody type. Interobserver reliability was calculated using pair-wise kappa. Following discussion of the results, the Phase Two study was planned. Lab 2 and Lab 3 independently performed the HER2 staining according to the protocol for 60 invasive breast carcinoma cases. The same group of pathologists scored 2 x 60 stained slides that were masked for laboratories. Interobserver reliability and interlaboratory agreement from each pathologist were calculated using kappa statistics. Three interpreted categories--namely negative, equivocal and positive tests were used in the analyses.


RESULTS
Phase One study showed interobserver agreement between pairs varied from kappa 0.75 (95%CI, 0.68-0.82) to 0.06 (95%CI, 0-0.14) while Phase Two study obtained pair-wise kappa scores ranged from 0.84 (95%CI, 0. 80-0.89) to 0. 65 (95%CI, 0.59-0.71). Interlaboratory kappa for each pathologist was 0.67 (95%CI, 0.61-0.73).


CONCLUSIONS
The standardization of HER2 immunohistochemical assay was achieved through this two-phase study model. It had added benefits of improving pathologists' expertise and verifying the HER2 testing protocol to be used in Thailand.
Sampatanukul
Pichet
P
Department of Pathology, Faculty of Medicine, Chulalongkorn University, Bangkok 10330, Thailand. fmedpst@md2.md.chula.ac.th
Chaiwun
Benjaporn
B
Wongwaisayawan
Sansanee
S
Suwanagool
Parvinee
P
Vinyuvat
Songkhun
S
Karalak
Anant
A
Praditphol
Niphon
N
Paueksakon
Paisit
P
Ruangvejvorachai
Preecha
P
Field
Andrew S
AS
Wannakrairot
Pongsak
P
D001943:Breast Neoplasms / Q000175:diagnosis* / Q000473:pathology; D018270:Carcinoma, Ductal, Breast / Q000175:diagnosis* / Q000473:pathology; D002985:Clinical Protocols; D004396:Coloring Agents; D005260:Female; D018734:Genes, erbB-2 / Q000276:immunology*; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods / Q000592:standards*; D008962:Models, Theoretical; D010338:Pathology, Clinical / Q000379:methods / Q000592:standards*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000276:immunology*; D013785:Thailand
D004396:Coloring Agents; D018719:Erb-b2 Receptor Tyrosine Kinases