OBJECTIVETo investigate the variation of serum thyroid transcription factor-1 (TTF-1) in different patients and explore its significance in the diagnosis of lung carcinoma.

METHODSDot-enzyme linked immunosorbent assay (dot-ELISA) and Leica Q500 MC image analysis system were used to quantitatively detect TTF-1 protein in the serum samples from normal healthy adults and from patients with benign lung disease, lung cancer, thyroid carcinoma and non-thyroid carcinoma.

RESULTSThe sensitivity, specificity, standardized positive predicative value, standardized negative predicative value, standardized accuracy and standardized wrong diagnostic rate of the method were 90.91%, 82.22%, 83.64%, 90.04%, 86.57% and 13.43%, respectively. The cutoff value of serum TTF-1 in healthy normal adults was 36.39, with a ROC value of 0.95. Serum TTF-1 PU was significantly higher in patients with lung adenocarcinoma, squamous cell lung carcinoma and thyroid carcinoma than in healthy adults and patients with benign lung diseases and non-thyroid carcinoma (P=0.000). Serum TTF-1 PU was similar in lung adenocarcinoma, squamous cell lung carcinoma, small cell lung carcinoma, large cell lung carcinoma and thyroid carcinoma (P=0.744, 0.677, and 0.333, respectively). Serum TTF-1 PU was greater than the PU in the corresponding homogenate of lung adenocarcinoma, squamous cell lung carcinoma, small cell lung carcinoma, large cell lung carcinoma and thyroid carcinoma (P=0.000). Serum and homogenate TTF-1 PU was correlated to TNM stage of lung cancer patients (P=0.000) but not to gender, tumor types, differentiation or lymph node metastasis.

CONCLUSIONSLung adenocarcinoma, squamous cell lung carcinoma and thyroid carcinoma are suspected when serum TTF-1 PU is higher than 36.39. Serum TTF-1 is not helpful in differentiating the types of lung carcinomas and thyroid carcinoma. After exclusion of thyroid carcinoma, detection of serum TTF-1 can be helpful in the diagnosis of lung cancer. In different lung carcinomas and thyroid carcinomas, the serum TTF-1 is higher than the corresponding homogenate TTF-1 level. Serum TTF-1 increases with the progression of TNM stage of lung carcinoma.