Circulating immune complex refers to the antigen-antibody complex formed after the combination of antigen and antibody, which will enter the blood circulation and deposit on the blood vessel wall, triggering an abnormal immune response, thus causing a series of diseases, such as rheumatoid arthritis, systemic lupus erythematosus, polyarteritis nodosa, glomerulonephritis, etc. The molecular weight of circulating immune complex is about 1000kD. The molecular weight of circulating immune complexes is about 1000kD, and they are mainly detected by blood tests. Generally speaking, the body will remove the immune complexes through phagocytosis system, and the circulating immune complexes test result will be negative at that time. However, if the patient suffers from a certain disease, the immune complexes cannot be completely removed, which leads to infection, tissue damage, tissue edema and thrombosis, etc. Common diseases include vasculitis, glomerulonephritis, and so on. The circulating immune complex test is of clinical significance for the diagnosis of rheumatoid arthritis, systemic lupus erythematosus, polyarteritis nodosa and other rheumatic immune diseases, as well as acute glomerulonephritis, membranous nephritis, hepatitis B, dengue fever and other diseases. Before the test, you should try to fast from the night before so as not to affect the test results. If the test shows abnormal results, it is necessary to go to the hospital in time to clarify the cause of the disease.