Abstract: A method of detecting an inflammatory disease or a cancer in a test subject comprising determining the amount of plasmenyl-PE or a biomarker having a mass charge ratio of approximately 698.2, 722.2, 726.2 or 750.2 in a sample of bodily fluid taken from the test subject and comparing the amount of plasmenyl-PE (or the biomarker) in the sample of the bodily fluid from the test subject to a range of amounts of plasmenyl-PE (or the biomarker) found in samples of the bodily fluid from a group of normal subjects of the same species as the test subject and lacking the inflammatory disease or the cancer, whereby a change in the amount of the plasmenyl-PE (or the biomarker) (such as a lower amount) in the sample of the bodily fluid from the test subject indicates the presence of the inflammatory disease or the cancer.