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Head-to-Head Comparison of HER2 Testing Identifies Advantages of Dako's Dx over Abbott's

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Originally published July 8

NEW YORK (GenomeWeb) – A head-to-head comparison of Dako's HER2 IQFISH pharmDx kit against Abbott's PathVysion HER2 DNA Probe kit highlighted a few key advantages of Dako's test over Abbott's.

The comparison was conducted by Dallas, Tex.-based anatomic pathology laboratory ProPath Services. The lab conducted an eight month study analyzing 1,500 formalin-fixed paraffin-embedded tissue sections with the two kits. Both tests are approved by the US Food and Drug Administration as tools that doctors can use to gauge which breast and gastric cancer patients have HER2 gene amplification and would benefit from treatment with drugs targeting the protein, such as Herceptin (trastuzumab).

"There was 100 percent concordance of the HER2 assessment result from both assays, with six HER2-amplified specimens, and 15 HER2-non-amplified specimens with both assays," according to white paper written by Debra Cohen, ProPath's cytogenetics, flow, and molecular laboratory manager, and Sharon Alsobrook, lead cytogenetic technologist at the lab.

However, the two tests differed in terms of hybridization time, signal-to-background ratio, hands-on-time, costs, and turnaround time for results. "The PathVysion assay required 17 hour hybridization, while the HER2 IQFISH required 1.5 hour hybridization," the report states.

Additionally, technologists had to clean up background signals in order to better view the image captured from the PathVysion test, which added between 10 minutes and 40 minutes to the analysis time. Comparatively, captured images from the Dako assay didn't need to be cleaned up that often, and when they did, technologists could do it in less than a minute, the report states.

During the eight-month study, 37 of the more than 1,300 specimens tested with PathVysion had to be repeated. The HER2 IQFISH had to be repeated on 6 out of nearly 1,500 specimens. The reduced repeat rate using Dako's test resulted in a cost savings of $6,500 over eight months, or $4.70 per slide.

Moreover, ProPath was able to report results from the HER2 IQFISH test for 37 percent of samples in one day or less, while only 13 percent of samples tested by PathVysion had the same turnaround time.

"The reduction in the number of repeat tests, and the increased efficiency in processing resulted in pronounced savings in our lab," Cohen and Alsobrook wrote in the white paper. "Our laboratory now uses the HER2 IQFISH pharmDx assay for all HER2 FISH testing."

The study authors said they had no conflicts of interest. Dako, a subsidiary of Agilent Technologies, paid for the graphical design and for printing the white paper.

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