Overall, 20 of the 25 firms in the index saw their share prices grow in May, including seven whose stocks rose more than 20 percent compared to April.
Opko has until July 5 to comment on the proposed non-coverage local coverage determination, the most recent development in the test's twisted Medicare narrative.
Service revenues were down 8 percent year over year, product revenues grew 26 percent, and revenues from the transfer of intellectual property inched up less than 1 percent.
The share prices of 20 companies in the 360Dx Index rose last month, with Exact Sciences, Natera, Invitae, and NeoGenomics the biggest gainers.
In a study looking at 4,000-plus men, the test identified patients with elevated PSA levels but low risk of dying from prostate cancer over the next 20 years.
The 360Dx Index was down 3 percent in February, reflecting similar losses in the broader markets. GenMark Diagnostics and Opko Health were the biggest decliners.
Several firms, such as Exact Sciences and Foundation Medicine, saw their share values more than double during the year, while NantHealth and GenMark saw their share values shrink.
Paced by Accelerate Diagnostics and Bio-Rad, the 360Dx Index beat the broader markets. Shares of GenMark and Opko, however, were sharply down.
Opko subsidiary Bio-Reference Laboratories is retiring GeneTests.org next month given the availability of the NIH-backed Genetic Testing Registry.
Revenues at BioReference Labs fell short in the quarter but are expected to grow in the fourth quarter and next year, the company said