Q-Probes studies in anatomic pathology: quality improvement through targeted benchmarking

CONTEXT

The Q-Probes program is a peer-comparison quality assurance service offered by the College of American Pathologists that was created in 1989.

OBJECTIVE

To establish national benchmarks around a specific quality metric at a specific point in time in anatomic pathology (AP).

DESIGN

Q-Probes are based on a voluntary subscription for an individual study. Hospital-based laboratories in the United States, Canada, and 16 other countries have participated. Approximately one-third of all Q-Probes studies address AP metrics. Each Q-Probes study has a primary quality indicator and additional minor indicators.

RESULTS

There have been 52 AP Q-Probes studies addressing process-, outcome-, and structure-related quality assurance issues. These Q-Probes studies often represented the first standardized national benchmark for specific metrics in the disciplines of cytopathology, surgical pathology, and autopsy pathology, and as such have been cited more than 1700 times in peer-reviewed literature. The AP Q-Probes studies that have been repeated over time demonstrate improvement in laboratory performance across an international spectrum.

CONCLUSIONS

The Q-Probes program has produced important national benchmarks in AP, addressing preanalytic, analytic, and postanalytic factors in the disciplines of cytopathology, surgical pathology, and autopsy pathology. Q-Probes study data have been published, cited, and used in the creation of laboratory accreditation standards and other national guidelines.

Correlation between HER2 determined by fluorescence in situ hybridization and reverse transcription-polymerase chain reaction of the oncotype DX test

The human epidermal growth factor receptor 2 (HER2) gene is amplified and its protein product overexpressed in about 20% of invasive breast cancers. Despite more than a decade of efforts to standardize HER2 testing, controversy persists regarding the most optimal testing method. Recently, Oncotype DX reports have begun including HER2 results in addition to the previously reported Recurrence Score. We compared HER2 results obtained by fluorescence in situ hybridization (FISH) in our laboratories with HER2 results obtained by reverse transcription-polymerase chain reaction (RT-PCR) as documented in the Oncotype DX report. We then sought to identify potentially significant characteristics in the discrepant cases. We identified breast cancer patients with estrogen receptor-positive, lymph node-negative tumors who had Oncotype DX testing performed between September 2008 and March 2012. Patient and tumor characteristics including HER2 FISH and Oncotype DX test results were recorded. Image analysis was performed on cases with discrepancy between the HER2 FISH and Oncotype DX HER2 results to determine the relative proportion of invasive tumor. Eight of 194 (4.1%) cases showed discrepancy between HER2 FISH and Oncotype DX RT-PCR results. Although the overall percent agreement (96%) and percent negative agreement (100%) were high, percent positive agreement was only 50%. Three of 8 (38%) discrepant cases showed heterogeneous amplification by FISH. Seven of 8 (88%) discrepant cases had <50% invasive tumor in the Oncotype DX tissue block. Percent positive agreement between HER2 FISH and Oncotype DX RT-PCR is low. Multiple factors may contribute to this discrepancy including a suboptimal microdissection and possibly heterogeneous amplification of HER2 gene in some cases.

False positivity in HER2 testing of breast cancer: novel paths for approaching an old dilemma

AIMS

Variability in determining HER2 status has been reported, especially, differences in sensitivity and specificity among commercially available antibodies, with false positive and false negative results. We compared the sensitivity and specificity of five anti-HER2 antibodies by immunohistochemistry (IHC), using the new dual colour brightfield in situ hybridisation (DDISH) as the gold standard, on invasive breast carcinomas (IBC) arrays.

MATERIAL AND METHODS

Serial sections from tissue microarrays (TMA) containing 200 preselected primary IBC were submitted to DDISH (VENTANA INFORM HER2 Dual ISH assay), and immunohistochemistry, using Dako A0485 and HercepTest (polyclonal), Novocastra CB11 (mouse monoclonal), NeoMarkers SP3 and Ventana 4B5 (rabbit monoclonal).

RESULTS

From the initial 200 cases, 184 were assessed by DDISH and IHC. The concordance among the antibodies was considered very good (kappa statistics varied from 0.82 to 0.9). The overall concordance between IHC and DDISH ranged from 94.1% for CB11 to 96.6% for A0485. The antibodies A0485, HercepTest, SP3 and 4B5 were over 95% sensitive and specific. CB11 was the most specific antibody (97.1%). 60% (CB11) to 83.3% (SP3) of the 2+ cases showed no gene amplification by DDISH. False negative cases varied from 0.5% (A0485) to 3.8% (CB11) of the cases, and false positive from 1.6% (CB11) to 2.7% (HercepTest, SP3 and 4B5) of the 184 cases.

CONCLUSIONS

There was very good agreement among the five anti-HER2 antibodies. CB11 was the most specific antibody, but showed more false negative cases. A0485, SP3, 4B5 and HercepTest were highly sensitive and specific, but showed more false positive cases.