Inherited metabolic disorders include abnormalities of amino acid, organic acid, fatty acid and sugar metabolism and lysosomal storage diseases. In the past, due to the limitation of detection methods, children with these hereditary metabolic diseases were not diagnosed in time and were considered as “rare” diseases. In recent years, tandem mass spectrometry (MS/MS) has been developed internationally to detect amino acid and acylcarnitine profiles in dried blood filter paper, providing technical support for rapid clinical diagnosis of amino acid, organic acid and fatty acid metabolic diseases, combined with gas chromatography-mass spectrometry (GC-MS). spectrometry (GC-MS) for urinary organic acid detection, which makes the diagnosis more reliable and promotes the screening, diagnosis and treatment of hereditary metabolic diseases. Tandem mass spectrometry is a technique for the qualitative and quantitative analysis of substances by detecting the mass-to-charge ratio (relative molecular mass) of substances in a sample, and can simultaneously detect more than 70 amino acids and acylcarnitines in a drop of blood, allowing rapid screening and diagnosis of more than 40 amino acid, organic acid and fatty acid oxidative metabolic diseases, the prevalence of which is shown in Table 1. tandem mass spectrometry has been used in many countries for neonatal Tandem mass spectrometry has been used in many countries for newborn screening and detection of clinically suspected patients, resulting in a significant increase in the prevalence of related diseases. Gas chromatography-mass spectrometry (GC-MS) is a technique used to detect organic acids in urine as an aid or differential diagnosis of oxidative metabolic diseases of amino acids, organic acids and fatty acids. Our country started to use gas chromatography-mass spectrometry for genetic metabolic disease detection in 2000, and tandem mass spectrometry for newborn screening of genetic metabolic diseases and detection of patients with clinical suspected genetic metabolic diseases in 2002, which has significantly improved the screening, diagnosis and treatment technology of genetic metabolic diseases in China. Shanghai Xinhua Hospital used tandem mass spectrometry to screen 269,341 newborns and detected 74 cases of 14 genetic metabolic diseases, with a positive rate of 1/3640, see Table 2. 12,100 children with clinically suspected genetic metabolic diseases were detected by combined gas phase mass spectrometry, and 703 cases of genetic metabolic diseases were confirmed, with a diagnosis rate of 5.8%, among which phenylketonuria and methylmalonic acidemia are common. Amino acid metabolic diseases are mainly due to the blockage of amino acid metabolic pathways leading to the increase or decrease of the corresponding amino acid levels in the body and the corresponding increase of its bypass metabolites, organic acids, which cause damage to the organism. Tandem mass spectrometry detects amino acid metabolic disorders by measuring amino acid levels in blood filter paper and the ratio between related amino acids. Gas chromatography-mass spectrometry detects organic acids in the patient’s urine as an aid to diagnosis. Tandem mass spectrometry is specific for the detection of hyperphenylalaninemia, maple diabetes mellitus, citrullinemia, tyrosinemia, citrullinemia and argininemia. Since both transcarbamylphosphate synthase deficiency and ornithine transcarbamyltransferase deficiency (OTCD) exhibit reduced citrulline, tandem mass spectrometry is used to identify those whose reduced blood citrulline is required in combination with gas chromatography-mass spectrometry for urinary orotate and uracil levels, with elevated levels being OTCD and normal levels being transcarbamylphosphate synthase deficiency. There are three types of tyrosinemia, all of which show increased tyrosine by tandem mass spectrometry. Those with increased succinic acid acetone, 4-hydroxyphenylpyruvic acid, and 4-hydroxyphenyllactic acid by gas chromatography-mass spectrometry are type I, and those with increased 4-hydroxyphenylpyruvic acid and 4-hydroxyphenyllactic acid only are type II or type III. Organic acidemia is a group of genetic metabolic diseases, including more than 10 diseases such as MMA, PA, IVA, MCC, HMG, GA-I, GA-II, biotinase deficiency and total carboxylase synthase deficiency. Due to the blockage of the further metabolic pathway of organic acids produced during the metabolism of proteins, fats or sugars, the organic acids in the body increase in large amounts, which is harmful to the body. The excessive organic acids in the body combine with free carnitine to form acyl carnitine with different carbon chain lengths on the one hand, and are excreted through the urine on the other hand, and the level of organic acids in the urine of patients increases greatly. Tandem mass spectrometry detects organic acidemia by measuring blood acylcarnitine levels, and gas chromatography-mass spectrometry detects organic acidemia by measuring urinary organic acid levels. Among organic acidemia MMA is the most common in our country. Fatty acid oxidative metabolic disorders are a group of disorders resulting from impaired fatty acid oxidation due to dysfunction of the required enzymes during fatty acid entry into the mitochondrial pathway or fatty acid b-oxidation. These diseases are difficult to diagnose due to the lack of specific clinical manifestations and routine laboratory tests. Free carnitine and acylcarnitine are essential substances and intermediate products of fatty acid oxidative metabolism, so impaired fatty acid oxidative metabolism leads to an increase or decrease of free carnitine or acylcarnitine in the body, so the level of free carnitine or acylcarnitine in blood can be measured by tandem mass spectrometry, and fatty acid metabolic diseases can be screened and diagnosed according to the changes in the level of acylcarnitine of different carbon chain lengths. When fatty acid b oxidation is blocked, the w oxidation pathway is enhanced, so dicarboxylic aciduria appears in the urine, but is not specific. The prevalence of fatty acid b-oxidation metabolic diseases is high in Europe and the United States, with medium-chain acyl coenzyme A dehydrogenase deficiency being the most common, with a prevalence of 1:8,100 to 1:20,000 in the Caucasian population. With the exception of a few amino acid diseases, most of these diseases lack specific clinical signs and symptoms of amino acid, organic acid, and fatty acid b-oxidation metabolic diseases, with feeding difficulties, vomiting, lethargy, coma, and convulsions predominating in the neonatal period and in infants and children. In the neonatal period, feeding difficulties, vomiting, lethargy, coma and convulsions are the main symptoms. On physical examination, microcephaly, hepatomegaly, and cardiomegaly are common. Routine laboratory tests with moderate acidity, high blood ammonia, increased lactate, hypoglycemia, and increased creatine kinase are common. Therefore, when a child with the above clinical manifestations of unknown cause is encountered, the possibility of hereditary metabolic disease should be considered, and blood or urine samples should be retained for specific testing of amino acids, acylcarnitine and organic acid analysis to avoid delay in diagnosis and treatment. In addition, tandem mass spectrometry uses dried blood filter paper, and gas phase mass spectrometry can use fresh urine or dried urine filter paper, so sample collection and delivery is convenient, which facilitates remote delivery of specimens and helps to provide services to patients in the field.