A method of detecting the presence or absence of a disease in a patient wherein said disease is accompanied by deficient levels of S-adenosylmethionine comprising: identifying a patient that is suspected of having said disease or is at risk of having said disease； obtaining a biological sample from said patient； determining the level of S-adenosylmethionine in said biological sample using an antibody derived from a hapten analog of S-adenosylmethionine； and correlating the level of S-adenosylmethionine in said biological sample with the presence or absence of said disease. The invention also provides methods for measuring SAH which is used to determine the methylation index (ratio of SAM/SAH) in biological fluids which is indicative of the health status of an individual.
