OBJECTIVETo evaluate efficacy of sputum imaging cytometry in early diagnosis on lung cancer among tin miners exposed to dust and analyze possible risk factors related to lung cancer among tin miners.

METHODSFrom a cohort of tin miners in Guangxi Province, a total of 345 male tin miners higher than 45 years old and with high exposure to crystalline silica dust were randomly selected as the objects. Imaging cytometry was used to implement the sputum analysis for the screening on lung cancer according to the experience diagnostic standard. All objects were then followed up to the end of 2006. Clinical diagnosis of lung cancer was used as the golden standard to evaluate the efficacy of screening.

RESULTSFrom 1998 to 2006, 11 new cases were diagnosed as clinical lung cancer. Except of age and exposure to occupational hazards, smoking status (P = 0.0384) and mean smoking dose (P = 0.0078) were significantly associated with lung cancer, and the adjusted odds ratio of high level to the low was 18.21 (2.15 approximately 154.39). The sensitivity, specificity and Youden's index of the sputum imaging cytometry for the experience diagnosis were 27.3%, 83.9% and 11.2% respectively. According to the ROC curve analysis, area under ROC Curve (AUC) of C2.5 (the percentage when the DNA index ranged from 1.25 to 2.50) was 0.647 (0.525 approximately 0.768), with the optimal operating point (OOP) of 1.70%. Sensitivity, specificity, agreement rate, positive predictive value, negative predictive value and Youden's index for predicting lung cancers in high-exposure tin miners were found to be 72.7%, 62.3%, 62.6%, 6.0%, 98.6% and 35.0% respectively.

CONCLUSIONSmoking is confirmed as an important risk factor of lung cancer in tin miners. The diagnostic efficiency can be improved if the diagnostic point of C2.5 is adjusted to 1.70%.