A two-phase study model for the standardization of HER2 immunohistochemical assay on invasive ductal carcinoma of the breast
Sampatanukul, P.; Chaiwun, B.; Wongwaisayawan, S.; Suwanagool, P.; Vinyuvat, S.; Karalak, A.; Praditphol, N.; Paueksakon, P.; Ruangvejvorachai, P.; Field, A.S.; Wannakrairot, P.
Journal of the Medical Association of Thailand 88(11): 1680-1688
2005
ISSN/ISBN: 0125-2208 PMID: 16471119 Document Number: 8172
To develop and verify a standardized protocol for HER2 immunohistochemical assays on invasive ductal carcinoma of the breast in Thailand. 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. 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). 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.
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