"Tissue of Origin" Genomic Test Receives FDA Approval

Although I have not practiced surgical pathology for many years, I still have very vivid memories of examining the cells of poorly differentiated lesions under the microscope for clues about their tissue of origin. Even in those days, such information was important for oncologists in order to select the optimal chemotherapy for patients. We now learn of the announcement of a new test for "tissue of origin" of malignant lesions (see: FDA Clears the Pathwork Tissue of Origin Test for Hard-To-Identify Tumors). Below is an excerpt from the press release with boldface emphasis mine:

Pathwork Diagnostics, a molecular diagnostics company focused on oncology, today announced that the U.S. Food and Drug Administration (FDA) has cleared its Pathwork Tissue of Origin Test for use in determining the origin of uncertain tumors. The test analyzes a tumor's gene expression pattern to help pinpoint the source of hard-to-identify tumors and is the first test of its kind to receive FDA clearance...The FDA-cleared Pathwork Tissue of Origin Test will be available as an in vitro diagnostic (IVD) kit, meaning that clinical laboratories can run the test themselves. The test is currently available as a service through Pathwork's CLIA-certified laboratory. The Pathwork Tissue of Origin Test uses a microarray to measure the expression pattern, comprising more than 1,500 genes, in the uncertain tumor and compares it to expression patterns of a panel of 15 known tumor types, representing 60 morphologies overall, to help determine the tumor's origin. In the in vitro diagnostics clinical validation study submitted to the FDA, the test demonstrated 89 percent positive agreement (akin to sensitivity) with available diagnoses and 99 percent negative agreement (akin to specificity).

Although the "tissue of origin" test is available as an in-vitro diagnostic kit as noted above, it will only be the most sophisticated labs that will be able support the necessary tissue microarray (TMA) technology. For this reason, Pathwork Diagnostics will also offer the test in its own laboratory. In a previous note, I discussed sensitivity and specificity (see: Defining Test Sensitivity and Specificity for the General Public), defined as the ability to detect a true positive and a true negative. The new test demonstrated very high percentages of positive and negative agreement which are described as being akin to sensitivity and specificity. Positive and negative agreement are raw agreement indices, important descriptive statistics with unique common-sense value.

Comments

[Glenda G Anderson]

As founder of Pathwork and its technology, it is very encouraging to hear that you have found the raw agreement indices to be "important descriptive statistics with unique common-sense value". We worked particularly hard on this aspect of the product with a hope to accomplish just that.

You likely share my belief that result reporting is an oft overlooked, but critically important element of good clinical diagnostic product design.

Wanted to offer one correction. The test uses a high density oligonucleotide microarray (in fact, a GeneChip), not a tissue microarray. A test of this sort requires the high level of platform reproducibility available only from the former.

Best regards,
GGAnderson