Study Of The Application Of The GC-MS In The Diagnosis And Treatment Of The Urea Cycle Defect

Objectives1.Compare the Gas chromatography-Mass spectrometry(GC-MS) analysis method with the urine colorimetry method in the diagnosis of the inherit metabolic disease.2.Compare the metabolic products in urine before and after the treatment of the children patients suffering from urea cycle defect with the normal children.The GC-MS can be applied in the diagnosis and treatment of the urea cycle defect.Methods1.Take the urine as the experimental sensitivity sample of the 68 cases of the children patients with hyperammoniemia and 30 cases of normal healthy children.2.Obtain the urine samples of 10 cases of children patients with the urea cycle disorder before and after treatment and 60 cases of normal healthy children.3.Several common colorimetry methods are applied to determinate the metabolic products in urine.4.Treat the urine with the urease to eliminate the urea,then determinate the metabolic products by GC-MS.5.Determinate the chemical composition of the metabolic products of urine by the mass spectrometer to definite NIST spectrum in the database.6.Take the n-heptadecane acid as internal standard substance,then quantify the metabolic products with endogeny creatinine as the internal standard.Results1.The results of the urine colorimetry is that 5 cases in 68 cases patients were definited be abnormal,including 2 cases(2.9%) of metabolic disease(tyrosinemia),3 cases of non-metabolic disease. 2.The results of the urine GC-MG analysis is that 22 cases(32.35%) in 68 cases patients were definited to be abnormal,including 3 cases of methylmalonic acidemia, 2 cases of propionic acidemia,3 cases of tyrosinemia,4 cases of multiple carboxylase deficiency,and 10 cases of urea cycle defect.The results of 22 cases is match at 100% with the diagnosis which have been diagnosed by the Institute of metabolism and endocrine in the Department of Pediatrics in Tongji Hospital attached with Huazhong University of Science and Technology.3.The metabolic products in the urine of the children patients with urea cycle defect mainly contain orotic acid and uracil,comparing with the normal healthy children,the metabolic products of orotic acid and uracil of the children patients with urea cycle defect were obvious higher before the treatment(P＜0.05),the content of orotic acid was 294.7(22.5～823.0) mmol/mol creatinine and the content of uracil was 130.9 (5.8～278.0) mmol/mol creatinine.But the content of orotic acid and uracil in the healthy children were 1.5 mmol/mol creatinine(untestable～6.5) and 0.6 mmol/mol (untestable～3.3) creatinine.4.The content of orotic acid and uracil in urine of the children patients with the urea cycle defect were obviously lower and could not be detect after the treatment comparing with before(P＜0.05).Conclusion1.The urine GC-MS analysis is obviously better than the urine colorimetry method in the diagnosis of the inborn inherits metabolism disease.2.The urine analysis can help the doctor to diagnose accurately in the urea cycle defect.The orotic ac??nd uracil in urine-test suggest the urine cycle defect,we could identify this disease from other related disease by the urine GC-MS analysis.