Abstract: The present invention relates to methods for detecting JAK2 nucleic acid in acellular bodily fluid samples from patients with neoplastic disease and determining if the nucleic acid contains one or more mutations or one mutation and one deletion. The methods are useful for diagnosing patients that have cells with mutations in the JAK2 gene that effect kinase activity. The detection of such mutations can be used to determine treatment for patients or stratifying patients for therapy and management.