Evaluation of tumor-associated antigens and total sialic acid levels in effusions of malignant and benign origin.

Abstract

Cytological examination is the most commonly used diagnostic procedure in the differential diagnosis of pleural effusions although the sensitivity of this method in malignancy compared with more invasive procedures is only about 60 'YO Several studies have tried to increase the sensitivity of the cytological examination by using additional immunological or serological methods such as the determination of lactate dehydrogenase, total protein content, tumor-associated antigens, DNA aneuploidea. or expression of different cellular antigens. While the analysis of cellular parameters requires some technical expertise, the detection of humoral factors is more simple. Especially tumor-associated antigens, released by the tumor cells into the effused fluid could possibly become significant in the diagnostic differentiation of the metastatic from the nonmetastatic or benign origin of effusions [ I ] . Of all tumor markers known to date, data are mostly available on CEA, indicating that the concentration of this antigen in effusions could improve the diagnostic accuracy of the cytological examination [ 2 , 3 ] . MCA (mucin-like carcinoma-associated antigen) is a high molecular weight glycoprotein (about 350 kD) which is also expressed in the majority of other adencarcinomas and in normal epithelial cells when detected by immunohistochemical methods[ I ] . Mucin-associated carbohydrate and peptide antigens are currently being investigated for their role in cancer diagnosis, monitoring for progression or metastases, immunotherapy and immunosupression 14-61, With respect to the premise that the new tumor marker MCA could be used as a diagnostic tool to detect metastasis-caused effusions, we determined the MCA concentrations in comparison wth the other carbohydrate antigens CA 19.9 and CA 125, as well as the well known tumor marker total sialic acid (TSA). in pleural effusions and in sera in lung carcinomas This study was undertaken in the Department of Biochemistrq., at Dokuz Eyliil University Medical Faculty, be twen September 1993 and February 1995: a total of 48 effusions were collected from 48 patients, who were subjected either to simple needle aspiration or to tube drainage for the diagnosis of a pleural effusion. Serum samples were obtained concurrently from all of these patients. All cytological examinations were carried out in the same sample as the tumor marker determinations. Classification of the groups were effectuated as follows ( I ) Malignant groups: 14 of those cases were suffering from histologically diagnosed lung malignancies (8 adenocarcinomas, 3 squamous cell carcinomas. 2 small cell carcinomas, and 1 malignant mesothelioma); (2) Benign group: 34 patients with various non-neoplastic disorders were included in this group (23 tuberculosis pleurisy, 5 pleuritis, 3 congestive heart disease, 2 pneumonia+cirrhosis, and I emppyema). The cut-off level between negative and positive ralues of each tumor marker was defined as the mean+2SD (% 95 percentile). Pleural effisions and uncoagulated blood samples were centrifuged at 2000 rpm for 10 minutes to remove cellular components. The supernatants were stored at -70 C until the performance of the tumor marker assays. The tumor markers MCA, CA 19.9 and CA 125 levels were measured in all samples by employing an enzyme-immunoassay method (EIA) (Hoffmann-La Roche, Basel, Switzerland). All measurements were done by the EIA photometer. automatically. The coefficients of lariation of the assays were determined to be as follows: the intra-assay coefficient of variation (CV) were 2.5 % for MCA, 3.4 %for CA 19.9, and 5.6 %for CA 125; the between-assay coefficients of variations ranged between 3.5 %and 9.6 % for MCA, 4.2 % and 11.5 % for CA 19.9, and 3.8 'Yo and 5.5 for CA 125. depending on the concentration of the control sera. TSA concentrations were determined by a modification of Ehrlich method. The reproducibility was checked at various sialic acid concentrations, and CV's were found to be <3.0 Yo in the whole measuring range. The lowest limit of detection defined as the concentration of N-acetylneuraminic acid that could be distinguished from blank with 95 YO confidence, was I mg/dl. The obtained tumor marker concentrations were statistically analyzed using the Student's-t test,Wilcoxon test, and Mann & Whitney test, accepting a p value below 5 Yo (p< 0.05) as significant. The results obtained for each group and for each tumor marker are presented in Table 1 Table I . MCA. CA 19.9. CA 125, and TSA in effusions and sera in lung cancer.