This study aims investigate the results of sputum cytology, which began its test period from 2009 as a special health examination for individuals whose lungs have been exposed to carcinogens.

22,215 cases of sputum results were classified into six categories through Papanicolau classification. The sputum results were analyzed according to age, exposure degree to welding fumes and smoking status. Chi-square tests and logistic regression analysis were used to compare and analyze the associations between sputum results and smoking status, exposure degree and age classifications.

The number of class I cases was 20,784 with a frequency of (93.6%), class II had 1,076 cases (4.8%), class III had 69 cases (0.3%), and the inadequate class had 286 cases (1.3%) and there were no cases in class VI and V. Patients in class III received CT scans of their chest for further evaluation, but no cancer patients were found from that. There were 2.48 times (95% CI 1.12~5.53) more smokers than non-smokers in class III and 1.70 times (95% CI 1.43~2.02) more in class II. The number of ex-smokers was 2.46 times (95% CI 1.01~5.99) larger than the number of non-smokers in class III and 1.28 times (95% CI 1.03~1.60) larger than the number of non-smokers in class II. There were 1.54 times (95% CI 1.28~1.85) more patients from the mid-exposure group than the low exposure group in class II. There were 1.62 times (95% CI 1.31~1.99) more patients from the high-exposure group than the low-exposure group in class II.

As a screening test for lung cancer, the usefulness of sputum cytology is limited. However, the precancerous cells (class II, class III) varied according to welding fume exposure degree and smoking status.