递送及储存条件对新生儿干血斑标本中氨基酸和肉碱浓度的影响

目的: 探讨不同递送和储存条件对新生儿干血斑标本中氨基酸和肉碱浓度的影响，为提高串联质谱筛查新生儿遗传代谢病的准确性及可靠性提供依据。方法: 根据不同递送和储存条件将1 254 616名在浙江省新生儿疾病筛查中心进行遗传代谢病筛查新生儿的干血斑标本分为3组：室温递送储存（室温组，n=338 467）、冷链递送+低温储存（冷链+低温组，n=480 021）、冷链递送+低温低湿储存（冷链+低温低湿组，n=436 128）。应用串联质谱技术检测干血斑标本中氨基酸和肉碱浓度，SPSS 24.0软件进行数据分析，分析递送和储存过程中温度和湿度对氨基酸和肉碱浓度稳定性的影响。结果: 三组样本氨基酸和肉碱浓度均呈偏态分布，氨基酸和肉碱浓度组间差异均有统计学意义（均P < 0.01）。酪氨酸浓度中位数冷链+低温组与冷链+低温低湿组相近，室温组较冷链+低温组和冷链+低温低湿组分别降低18%和16%；室温组的蛋氨酸浓度中位数与冷链+低温组相近，分别较冷链+低温低湿组降低15%和11%；3组精氨酸浓度中位数均有差异，室温组和冷链+低温组分别较冷链+低温低湿组降低12%和25%。室温组的游离肉碱浓度中位数与冷链+低温组相近，较冷链+低温低湿组增高12%。冷链+低温组的乙酰肉碱、丙酰肉碱、丙二酰肉碱+3-羟基-丁酰肉碱、戊二酰肉碱+3-羟基-己酰肉碱、十六碳酰肉碱等浓度中位数与冷链+低温低湿组相近，室温组较冷链+低温组和冷链+低温低湿组降低21%~64%。其他氨基酸和酰基肉碱浓度组间差异较小。除瓜氨酸、甲基丙二酰肉碱+3-羟基-异戊酰肉碱、戊酰基肉碱外，室温组其他氨基酸和肉碱浓度月中位数变异系数均高于冷链+低温组和冷链+低温低湿组。结论: 使用冷链递送和低温低湿储存可以有效延缓干血斑标本中部分氨基酸和肉碱的降解速度，提高串联质谱检测结果的准确性和可靠性，从而保证新生儿遗传代谢病筛查质量。

Effects of delivery and storage conditions on concentrations of amino acids and carnitines in neonatal dried blood spots

Objective: To explore effects of different delivery and storage conditions on concentrations of amino acids and carnitines in neonatal dried blood spots (DBS), so as to provide evidence for improving accurate and reliable detection by tandem mass spectrometry. Methods: A total of 1 254 616 newborn DBS samples in Newborn Screening Center of Zhejiang Province were delivered and stored at room temperature (group A, n=338 467), delivered by cold-chain logistics system and stored at low temperature (group B, n=480 021), or delivered by cold-chain logistics system and stored at low temperature and low humidity (group C, n= 436 128), respectively. The concentrations of amino acids and carnitines in DBS were detected by tandem mass spectrometry. Data analysis was performed by SPSS 24.0 to explore the influence of temperature and humidity on the concentrations of amino acids and carnitines. Results: The concentrations of amino acids and carnitines in the three groups were skewed, and the differences in amino acid and carnitine concentrations among groups were statistically significant (all P < 0.01). The median concentration of tyrosine was lower in group A than those in group B and group C by 18%and 16%respectively, while there was no significant difference between the last two groups. The median concentrations of methionine were lower in group A and group B than that in group C by 15%and 11%, respectively. The median concentrations of arginine were lower in group A and group B than that in group C by 12%and 25%, respectively. The median concentration of free carnitine (C0) was higher in group A than that in group C by 12%, while there was no significant difference between group A and group B. The median concentrations of acetylcarnitine (C2), propionyl carnitine (C3), C3DC+C4OH, C5DC+C6OH and hexadecanoyl carnitine (C16) were lower in group A than those in group B and group C by 21%-64%. The concentrations of other amino acids and acylcarnitines differed little among three groups. The monthly median coefficients of variation of other amino acids and carnitines in group A were higher than those in group B and group C except for citrulline, C4DC+C5OH and isovalerylcarnitine (C5). Conclusion: Cold-chain logistics system and storage in low temperature and low humidity can effectively reduce degradation of some amino acids and carnitines in DBS, improve the accuracy and reliability of detection, and thus ensures the quality of screening for neonatal metabolic diseases.