Labcorp (LH) has launched nationwide access to an FDA-approved companion diagnostic to identify patients with platinum-resistant ovarian cancer who may be eligible for treatment with Merck's (MRK) Keytruda, the company said Wednesday.

The Agilent-developed PD-L1 IHC 22C3 pharmDx test is the only FDA-approved companion diagnostic for this indication and helps clinicians identify eligible patients for Keytruda-based treatment regimens, Labcorp said.

Labcorp said the rollout is intended to expand access to precision testing and support treatment decisions for patients with limited options after developing resistance to platinum-based chemotherapy.