Urinary Uracil: A Useful Marker for Ornithine Transcarbamylase Deficiency in Affected Males

China nationwide landscape of 16 types inherited metabolic disorders: a retrospective analysis on 372,255 clinical cases

BACKGROUND

Inherited metabolic disorders (IMDs) usually occurs at young age and hence it severely threatening the health and life of young people. While so far there lacks a comprehensive study which can reveals China's nationwide landscape of IMDs. This study aimed to evaluate IMDs incidence and regional distributions in China at a national and province level to guide clinicians and policy makers.

METHODS

The retrospective study conducted from January 2012 to March 2021, we analyzed and characterized 372255 cases' clinical test information and diagnostic data from KingMed Diagnostics Laboratory. The samples were from 32 provincial regions of China, the urine organic acids were detected by gas chromatography-mass spectrometry (GC-MS), amino acids and acylcarnitines in dried blood spots were detected by liquid chromatography-tandem mass spectrometry (LC-MS/MS). We did a statistical analysis of the distribution of the 16 most common IMDs in amino acid disorders and organic acidemias, and then paid special attention to analyze the age and regional distributions of different IMDs. The statistical analyses and visualization analysis were performed with the programming language R (version 4.2.1).

RESULTS

There were 4911 positive cases diagnosed, which was 1.32% of the total sample during the ten-year study period. Most diseases tended to occur at ages younger than 18 year-old. The Ornithine Transcarbamylase Deficiency tended to progress on male infants who were less than 28 days old. While the peak of the positive case number of Citrin Deficiency disease (CD) was at 1-6 months. Different IMDs' had different distribution patterns in China's provinces. Methylmalonic Acidemias and Hyperphenylalaninemia had an imbalanced distribution pattern in China and its positive rate was significantly higher in North China than South China. Conversely, the positive rate of CD was significantly higher in South China than North China.

CONCLUSIONS

Results of this work, such as the differences in distribution pattern of different diseases in terms of age, region, etc. provide important insights and references for clinicians, researchers and healthcare policy makers. The policy makers could optimize the better health screening programs for covering children and infants in specific ages and regions based on our findings.

A Facile Method for the Quantification of Urinary Uracil Concentration by a Uracil-Specific Fluorescence Derivatization Reaction

A facile and reliable fluorescence method for the quantification of urinary uracil concentration is proposed herein. The assay utilizes a specific fluorescence (FL) derivatization reaction for uracil using 3-methylbenzamidoxime as a fluorogenic reagent. Although the presence of urine inhibited the FL reaction, 10 µL of urine was sufficient for the detection of urinary uracil. The uracil derivative was successfully separated from other fluorescent impurities using simple reversed-phase LC with FL detection. Urinary uracil concentrations from 16 people were compared with the concentrations obtained by the traditional column-switching liquid chromatographic analysis with UV detection. The FL derivative of uracil appeared as a single peak in the chromatograms of all samples. However, several samples showed an additional peak overlapping the uracil peak when using the column-switching method because of UV-active impurities. These results indicated that that the present method is not affected by interfering substances in urine and affords a precise determination of urinary uracil. We expect the proposed method to be applicable for diagnosing dihydropyrimidine dehydrogenase deficiency in 5-fluorouracil chemotherapy.