**3. Disease serum peptidomics research progress**

Nowadays in clinical detection, the serum biochemical indicators fail to accomplish the task of diagnosing complex diseases. For instance, there are only one or two serological diagnosis indicators available for specific cancers; even worse, these indicators cannot diagnose diseases independently and sometimes confuse the cancer with benign tumors or inflammation. For example, the prostate specific antigen (PSA) is a major diagnosis indicator for prostatic cancer, but not a biomarker for the prostatic cancer specificity, for the reason that 15%~25% prostatic cancer patients see their serum PSA falling into the normal range. Besides, PSA may also rise due to the benign hyperplasia of prostate, urinary infection, acute prostatitis, retention of urine and the per rectum operations. Accordingly, serum peptidomics analysis, as a new clinical diagnosis method, has made great progress in early diagnosis of complex diseases like tumor, neurological degenerative diseases and autoimmune disease.
