Plasma versus serum levels of osteopontin and mesothelin in patients with malignant mesothelioma—Which is best?

BackgroundBlood-based markers for malignant mesothelioma (MM), particularly soluble mesothelin and osteopontin, are currently of great clinical interest. As there is some concern about the sensitivity of osteopontin in serum versus plasma, we compared them in the same patient population to mesothelin.MethodsSoluble mesothelin and osteopontin concentrations were determined by commercial assays in blood samples from 66 patients with pleural MM, 47 patients with non-malignant asbestos-related lung or pleural disease, 42 patients with other benign pleural and lung diseases and 21 patients with lung cancer.ResultsSoluble mesothelin and osteopontin in serum and plasma were significantly elevated in MM patients compared to patients with benign lung and pleural disease. At a level of specificity of 95% relative to patients with benign disease, the sensitivity of mesothelin in serum and plasma at presentation with symptoms was 67%, and for osteopontin in the plasma was 40% and in the serum was 20% for MM patients. Combining the serum mesothelin and plasma osteopontin markers using a logistic regression model did not significantly increase the area under the receiver operator curve.ConclusionPlasma osteopontin has a superior diagnostic accuracy to serum. As the choice of blood sample type has limit effect on soluble mesothelin sensitivity, plasma should be collected for biomarker evaluation in patients suspected of having mesothelioma.