DIAGNOSTIC-VALUE OF SCC, CEA AND CYFRA-21.1 IN LUNG-CANCER - A BAYESIAN-ANALYSIS

The aim of this study was to evaluate the diagnostic value of three tu mour markers, squamous cell carcinoma (SCC) antigen, carcinoembryonic antigen (CEA) and CYFRA 21.1, in lung cancer using a Bayesian analysis to obtain the predictive values for different pretest probabilities o r prevalences. A cross-sectional study included 94 patients with lung cancer, 40 with benign lung disease, and 40 healthy controls, SCC anti gen and CEA were measured in blood samples by microparticle enzyme imm unoassay (MEIA), and CYFRA by enzyme-linked immunosorbent assay (ELISA ). The results of tumour marker determinations were expressed as perce ntiles, and showed significantly higher levels in the cancer group tha n in the two control groups. Taking the 95th percentile of benign lung diseases as the cut-off point (specificity 95%), the following sensit ivities were found: SCC 41%, CEA 31% and CYFRA 79%. After a Bayesian a nalysis, the best results for the three tumour markers were found in p revalences of 30-40%. The highest incremental gain was obtained by CYF RA (at prevalence of 36%, positive and negative predictive value appro ximately 90%). The three tumour markers were included in a stepwise re gression analysis to predict lung cancer, and CYFRA was the only selec ted variable. We conclude that CYFRA 21.1 may be a useful marker in lu ng cancer when there is an intermediate pretest probability of disease .