Pleural Fluid Mesothelin May Help Diagnose Mesothelioma

By Anthony J. Brown, MD

NEW YORK (Reuters Health) - Increased levels of the glycoprotein mesothelin in pleural fluid samples are associated with mesothelioma and may be useful in diagnosing the malignancy, according to a report in the September 1st issue of the American Journal of Respiratory and Critical Care Medicine.

Pleural effusion "can be maddeningly difficult to diagnose as a wide variety of malignant and benign causes exist," lead author Dr. Helen Davies, from Oxford University, said in a statement. "One of the causes, malignant pleural mesothelioma, is a relatively rare cancer, but its incidence is rapidly increasing on a global scale."

Serum mesothelin is a known biomarker for mesothelioma, but levels of the protein are much higher in pleural fluid and measuring such levels may improve the diagnosis of the malignancy.

In the current study, mesothelin levels were analyzed in pleural fluid samples from 166 patients with pleural effusions, including 24 with mesothelioma, 67 with other malignancies, and 75 with benign pleural effusion.

The median pleural fluid level of mesothelin in mesothelioma patients -- 40.3 nM -- was much higher than the levels seen in patients with other cancers benign effusions, 6.1 and 3.7 nM, respectively (p <>

For distinguishing mesothelioma from other causes of pleural effusion, mesothelin measurement had a sensitivity of 71%, specificity of 89%, and negative predictive value of 95%. The corresponding values with cytologic examination were 35%, 100%, and 82%.

With a "suspicious" cytologic reading, pleural fluid mesothelin was 100% specific for mesothelioma, the authors note. The negative predictive value with cytology-negative effusions was 94%.

The results also showed that when measured serially, there was little variation in pleural fluid mesothelin levels in patients with mesothelioma, just 0.15 nM with a 7-day test interval. Moreover, pleurodesis and the presence of bacteria did not influence the mesothelin results.

"Pleural fluid mesothelin provides a valuable adjunct in the diagnostic assessment of patients presenting with pleural effusions, especially when cytological examination is not definitive, and can improve clinical practice," Dr. Davies concluded.

Source:

Am J Respir Crit Care Med 2009;180:437-444. & www.cancerpage.com