Background Breathing alkanes are reported to be able to discriminate lung cancer patients from healthy people. with the chemiresistor sensor attached at its inside bottom to measure the sensor peak output (percentage change of baseline resistance measured before exhalation buy Maackiain to peak resistance) and the time taken for the baseline resistance to reach peak resistance. Results Analysis of multivariate variance and post-hoc Tukey test revealed that the peak output and the time to peak values for the lung cancer patients were statistically different from that for both the COPD patients and the controls without lung disease, Pillais Trace =0.393, F=3.909, df = (4, 64), P=0.007. A 2.20% sensor peak output and a 90-s time to peak gave 83.3% sensitivity and 88% specificity in diagnosing lung cancer. Tobacco smoking did not affect the diagnostic accuracy of the buy Maackiain sensor. Conclusions The alkane sensor could discriminate patients with lung cancer from COPD patients and people without lung disease. Its potential utility as a simple, cheap and non-invasive test for early lung cancer detection needs further studies. (10) reported that after gas chromatography-mass spectrometry (GC-MS) analysis of the exhaled breath, a predictive model employing only nine alkane compounds in the exhaled breath was sufficient to give adequate discrimination between lung cancer patients and healthy controls. Analysis of headspace of the lung cancer cell lines and healthy lung tissues using GC-MS confirmed that the concentration of expired alkane compounds differed between diseased and healthy state (11). The increased level of alkane compounds in the breath from the HMOX1 lung cancer patients is associated with the elevated oxidative stress in the lung neoplasms which promotes the peroxidation of polyunsaturated fatty acids (PUFAs) and produces greater amount of saturated hydrocarbons such as pentane and heptane (12). Besides lung cancer, it is known that long term cigarette smoking plays a significant role in the pathogenesis of chronic obstructive pulmonary disease (COPD), and several noninvasive oxidative stress biomarkers in the exhaled breath had been investigated to detect the development of COPD (13). Thus far, it is still unknown whether the differentiation between patients with buy Maackiain COPD, a population with an increased risk of developing lung cancer, and patients with lung cancer based on the level of alkane compounds is possible. Dragonieri (14) observed that patients with these two different buy Maackiain smoking-related diseases have different smellprints and an electronic nose with pattern recognition algorithm can separate the VOCs smellprints. However, in their study, the specific VOCs which differed between COPD patients and lung cancer patients remain unclear since an electronic nose does not give quantitative measure of the concentration of each VOC in the smellprints (15). The purpose of this study is to investigate the ability of a simple alkane sensor to differentiate the exhaled breath of lung cancer patients, patients with COPD and people without pulmonary disease. We hypothesize that there are significantly different levels of alkanes in the mixture of exhaled VOCs between patients with lung cancer and people without lung cancer. Methods Part 1 of the study: fabrication of the chemiresistor-based alkane sensor Chemiresistor-based alkane sensor A chemiresistor-based sensor consists of a chemiresistive film made up of organic compounds or semiconductor metal oxides that responds to the presence of VOCs by changing the resistance of the sensor (16,17). By measuring the change in resistance of the sensor, the concentration of the VOCs can be measured indirectly. In our study, we used a monomer composite to fabricate the chemiresistive film because it is cheap, operative under room temperature (17) and it can detect a mixture of alkanes in the presence of saturated water vapour (18). The composite film consisted of conductive carbon particles interspersed in an insulating monomer matrix. On exposure to buy Maackiain VOC gases, the VOC diffuses into the monomer composite causing the composite to swell, which then causes the dispersed conductive carbon particles in the composite to move further apart from each other. As a result, the resistance of the sensor.