Hollis Viray, Kevin Li, Thomas A. Long, Patricia Vasalos, Julia A. Bridge, Lawrence J. Jennings, Kevin C. Halling, Meera Hameed, and David L. Rimm (2013) A Prospective, Multi-Institutional Diagnostic Trial to Determine Pathologist Accuracy in Estimation of Percentage of Malignant Cells. Archives of Pathology & Laboratory Medicine: November 2013, Vol. 137, No. 11, pp. 1545-1549.

doi: http://dx.doi.org/10.5858/arpa.2012-0561-CP

CAP LABORATORY IMPROVEMENT PROGRAMS

A Prospective, Multi-Institutional Diagnostic Trial to Determine Pathologist Accuracy in Estimation of Percentage of Malignant Cells

Hollis Viray , BS; Kevin Li ; Thomas A. Long , MPH; Patricia Vasalos , BS; Julia A. Bridge , MD; Lawrence J. Jennings , MD; Kevin C.Halling , MD; Meera Hameed , MD; David L. Rimm , MD, PhD

From the Department of Pathology, Yale University School of Medicine, New Haven, Connecticut (Dr Viray, Mr Li, Dr Rimm); the Biostatistics (Mr Long) and Surveys (Ms Vasalos) Departments, College of American Pathologists, Northfield, Illinois; the Department of Pathology & Microbiology, University of Nebraska Medical Center, Omaha (Dr Bridge); the Department of Pathology & Laboratory Medicine, Northwestern University Feinberg School of Medicine, Chicago, Illinois (Dr Jennings); the Department of Pathology, Mayo Clinic, Rochester, Minnesota (Dr Halling); and the Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, New York (Dr Hameed).

Context.—The fraction of malignant cells in tumor tissue submitted for tests of genetic alterations is a critical variable in testing accuracy. That fraction is currently determined by pathologist visual estimation of the percentage of malignant cells. Inaccuracy could lead to a false-negative test result.

Objective.—To describe a prospective, multi-institutional study to determine pathologist estimation accuracy.

Design.—Ten ×20 magnification images of hematoxylin-eosin–stained colon tissue specimens were sent as an educational component of the College of American Pathologists KRAS-B 2011 Survey. Data from 194 labs were analyzed and compared to a criterion standard with comprehensive manual nuclear counts.

Results.—Survey responses indicated low interlaboratory precision of pathologist estimation, but mean estimates were fairly accurate. A total of 5 of the 10 cases assessed showed more than 10% of respondents overestimating in a manner that could lead to false-negative test results.

Conclusions.—The significance of estimation errors resulting in molecular testing failures with implications for patient care is unknown, but the current study suggests false-negative test results may occur.