The decision reversed a ruling by the U.S. Court of Appeals for the Federal Circuit, which specializes in patent issues.
Nestle, based in Vevey, Switzerland, acquired Prometheus last year.
Myriad, Novartis, Laboratory Corp. of America Holdings's Monogram Biosciences and Genomic Health Inc. all have urged that diagnostic methods be patentable. Monogram and Genomic Health told the Supreme Court in 2009 that they would have difficulty getting funding without patent protection.
The annual market for diagnostic tests and drugs tailored to individuals may reach $42 billion by 2015, according to a 2009 report from PricewaterhouseCoopers LLP.
The case is Mayo Collaborative Services v. Prometheus Laboratories, 10-1150.