The MESOMARK assay determines the levels of SMRP (soluble-mesothelin-related-peptide), a protein released into the blood by the cancerous cells of mesothelioma. A high concentration of SMRP may indicate mesothelioma long time before any asbestos-related cancer diagnosis is made. Doctors are advised to combine MESOMARK assay with other tests because there are types of mesothelioma that do not release high levels of SMRP or there are other diseases than mesothelioma that can increase the level of SMRP.