Sialic acid is an N - or O-substituted derivative of neuraminic acid, composed of a monosaccharide and a nine carbon backbone. The most common one is N-acetylneuraminic acid. Sialic acid is widely present in animal tissues in the form of glycoproteins and gangliosides, and is also distributed to a certain extent in plants, fungi, and yeast bacteria. The level of sialic acid is related to the developmental and pathological stages, and is used in clinical medicine for in vitro auxiliary diagnosis of inflammatory diseases and diseases associated with tissue destruction, such as malignant tumors. This reagent is used for in vitro quantitative determination of sialic acid content in human serum, and has clinical significance for early diagnosis and prognosis observation of malignant tumors. Principle: SA in serum is affected by neuraminidase to form N-acetylneuraminate, which in turn generates pyruvate and N-acetylmannosamine under the action of N-acetylneuraminate aldolase (NANA aldolase); Among them, pyruvate generates H2O2 under the action of pyruvate oxidase, and through the Trinder reaction, colored quinones are generated under the action of POD, causing an increase in absorbance at 540nm wavelength. By measuring the absorbance change at a wavelength of 540nm and comparing it with a calibration sample that has undergone the same treatment, the SA content in the sample can be calculated.