With the new test, patients can stay on their thyroid medicine. Based on the presence of genes for thyroglobulin, rather than on thyroglobulin itself, the test uses PCR to amplify very low level gene activity -- the sort you'd find with stray cells -- to the point where it can be detected. "The technique is extremely sensitive. It can tell, indirectly, if just one or two thyroid cells exist in a teaspoonful of blood," says Levine.
"What makes the test workable is that it needs only patients' blood. We didn't realize until now that everyone's blood contains circulating thyroid cells."
The test additionally avoids a rise in another hormone, thyroid stimulating hormone, which may encourage the growth of malignant thyroid cells. Some risk of this exists with present tests.
With an eye to widespread clinical use of the test, the research team is now clarifying whether stray cells are malignant or benign. They're also quantifying test results. "We should be able to follow levels of thyroglobulin gene activity in cancer patients -- the way you can follow HIV levels in AIDS patients -- to see how people respond to treatment. Ultimately," says Levine, "we hope assays like this will avoid the need to stop taking thyroid hormone and make monitoring faster, easier and more sensitive."
A similar assay using PCR to monitor prostate cancer treatment is being tested elsewhere.
Other researchers on the project were Matthew D. Ringel, M.D., and Paul W. Ladenson, M.D., both of Johns Hopkins. Funding for the project was from a United States Public Health Service grant and by Johns Hopkins.
'"/>
Contact: Marjorie Centofanti
mcentofanti@jhmi.edu
410-955-8725
Johns Hopkins Medical Institutions
1-Dec-1998