KLK3 and rheumatoid arthritis: Two studies helped to establish race-specific screening values for prostate-specific antigen (PSA) in young men.[51,52] Among findings most generalizable to the US population, several studies expanded the search for serum biomarkers in young adults that could be used to predict the subsequent onset of chronic illnesses such as systemic lupus erythematosus,[53,54,55,56,57,58] rheumatoid arthritis,[59,60,61] multiple sclerosis,[30,62] schizophrenia,[32,33,63,64,65] and non-Hodgkin lymphoma.[66]