Abstract: An embodiment of the present invention provides a method of creating a classifier indicative of a presence of a medical condition in a subject, comprising receiving chromatogram data indicative of a profile of volatile organic compounds in a sample from each of a first plurality of subjects having the medical condition and a second plurality of subjects without the medical condition, selecting one of the chromatogram data as reference chromatogram data, aligning the remaining chromatogram data in relation to the reference chromatogram data, extracting one or more features from the chromatogram data using a Mexican hat wavelet transform of one or more scales, selecting one or more features of the chromatogram data indicative of the medical condition, and constructing a classifier for determining a boundary between chromatogram data indicative of the medical condition and chromatogram data indicative of an absence of the medical condition.