A comparative study on detection of amino acids in newborns using two assay methods with tandem mass spectrometry

Abstract

Objective To provide methodological references for laboratories to carry out newborn screening for disorders of amino acid metabolism,we compared the difference and distribution of ten amino acids including alanine (Ala),arginine (Arg),citrulline (Cit),glycine (Gly),leucine (Leu),methionine (Met),ornithine (Orn),phenylalanine (Phe),tyrosine (Tyr),and valine (Val) from newborn dried blood spots specimen using derivatization or non-derivatization as sample preparation methods. Method It is a comparative research study.A total of 4135 newborn screening dried blood spot samples for inborn errors of metabolism were collected from January to June,2012.All specimens came from neonatal screening center of shanghai children′s hospital.Samples were prepared by two different techniques,the corresponding kits and the procedures were used as follows: (1) Simultaneous detection of 100 dried blood spot specimens using two methods respectively to compare the paired difference of each amino acid. (2) 2000 cases of normal newborn specimens were detected respectively to obtain the normal distribution of ten neonatal amino acids. (3) 35 specimens from patients previously diagnosed positively as inborn errors of metabolism were simultaneously detected with 7 amino acids to verify the consistency of two techniques in clinical judgment. Results The amino acid levels of normal newborns analyzed by one-sample kolmogorov-Smirnov test (Z value ranged from 1.997 to 6.229) showed a skewed distribution (P 0.05).According to 0.5th to 99.5th percentiles,the normal reference range for derivatization method were greater than onderivatization method,and the average value was 25.3%.After clinic judgment,the results of the abnormal indicators of children with true metabolism disorders showed no statistically significant between two methods (P>0.05),the detection rate was 100%. Conclusions There was a slight difference between derivatization and the non-derivatization techniques in detecting multiple amino acids.The results of the abnormal indicators of amino acid metabolism disorders show no statically significant difference between the two methods,and no difference in clinical judgment.Both methods can be used in detecting amino acid metabolism disorders in newborn screening.(Chin J Lab Med,2013,36:908-911) Key words: Amino acids; Tandem mass spectrometry; Specimen handling; Comparative study