The ability of life sciences companies to rely on patent protection for diagnostic methods has been eroded over the last ten years, although recent court decisions evidence a rebuilding framework. While courts have consistently invalidated diagnostic methods as lacking patent eligibility, claims re-framed as methods of treatment that include a diagnostic step have recently been deemed to be patent-eligible subject matter. In its recent decision in Illumina v. Ariosa, the Federal Circuit confirmed that another category of claims – methods of preparation – are patent- eligible, providing a new opportunity to cast diagnostic method claims in a patent-eligible light. The Court’s decision offers promise for patent applicants pursuing patent protection for COVID-19 and other diagnostic methods.