The invention generally relates to antibodies that bind to human folate receptor 1 and diagnostic assays for folate receptor 1 -based therapies. Methods of using the antibodies to monitor therapy are further provided. The present invention provides methods for detection of FOLRI in a sample and can be used, for example, to stratify patients. Thus, in one embodiment, the invention provides a method of treating a patient having a folate receptor 1 -mediated disease comprising: (a) measuring the shed folate receptor 1 (FOLRI) expression level or FOLRI on a circuiting tumor cell (CTC) in a sample taken from a patient.
