Usefulness of Thiocyanate as a Biological Marker for Discrimination of Smoking Status

Smokers have increased risk of death more than non-smokers due to its association with cancer, vascular and respiratory diseases, and tuberculosis. Epidemiological research has generally relied upon self-report information concerning smoking status but the validity is limited. Biochemical markers have been used in research on smoking are based on thiocyanate, nicotine, cotinine and carbon monoxide. Among them, thiocyanate is chosen as biomarker of smoking because of its long half-life. The aim of the study was to demonstrate the suitability of urinary, blood and salivary thiocynates (SCN‾) as indicators of smoking and to investigate the correlation among its content in salivary, serum and urinary SCN‾, and duration and amount of smoking. Thiocyanate levels were determined by spectrophotometric method in saliva, serum and urine samples to compare in smokers, passive smokers and non-smokers. The median saliva thiocyanate concentration of smokers [43.79(8.14-187.59 mg/ml)] was significantly higher (p<0.001) as compared to that of passive smokers [26.26(7.95-80.04 mg/ml)] and non-smokers [25.00(5.23-69.96 mg/ml)]. The salivary thiocyanate levels significantly correlated with duration of smoking in years (r=0.366) and number of cigarette smoking per day (r=0.316). Among three types of body fluids, saliva thiocyanate is the best biological marker for discrimination of smoking status. Heavy smokers can be distinguished from passive smokers and non-smokers by determination of thiocyanate level in saliva.