Simple urine test can help smokers know if they are at the risk of developing lung cancer or not; that's what a study has revealed. According to the study, lung cancer afflicts some smokers and not others.

The study by the University of Minnesota researchers has articulated that the presence of the metabolite NNAL in a patient''s urine might predict risk of lung cancer. NNAL has been shown to induce lung cancer in laboratory animals, but the effect in humans had not yet been examined.

Jian-Min Yuan, Ph. D., M. D., associate professor of public health at the University of Minnesota, said, "A history of smoking has always been thought of as a predictor of lung cancer, but it is actually not very accurate. Smoking absolutely increases your risk, but why it does so in some people but not others is a big question."

The researchers collected data from 18,244 men enrolled in the Shanghai Cohort Study and 63,257 men and women from the Singapore Chinese Health Study. They conducted in-person interviews to assess levels of cigarette smoking, dietary and other lifestyle factors, and collected blood and urine samples from more than 50,000 patients. For analyzing the impact of NNAL, they identified 246 current smokers who later developed lung cancer and 245 smokers who did not develop lung cancer during the 10-year period following initial interview and collection of urine samples. They then divided the levels of NNAL in the urine into three groups.

According to the study, the patients with a mid-range level of NNAL had a 43 percent increased risk of lung cancer, as compared to those with the lowest levels. On the other hand, those at the highest level had a more than two-fold increased risk of lung cancer after taking into account the effect of number of cigarettes per day, number of years of smoking, and urinary levels of cotinine on lung cancer risk.

Additionally, the researchers found that those with the highest levels of nicotine and NNAL had an 8.5-fold increase in the risk of lung cancer compared with smokers who had the lowest levels after accounting for smoking history.

Yuan said, "Smoking leads to lung cancer, but there are about 60 possible carcinogens in tobacco smoke, and the more accurately we can identify the culprit, the better we will become at predicting risk."