Laboratory Medicine ›› 2019, Vol. 34 ›› Issue (12): 1059-1065.DOI: 10.3969/j.issn.1673-8640.2019.12.001

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Role of tandem mass spectrometry for screening X-linked adrenoleukodystrophy

WANG Yanmin, TIAN Guoli, JI Wei   

  1. Neonatal Screening Center,Children's Hospital of Shanghai,Children's Hospital of Shanghai Jiaotong University,Shanghai 200040,China
  • Received:2018-12-20 Online:2019-12-30 Published:2020-01-03

Abstract:

Objective To establish a tandem mass spectrometry(MS/MS) for the determinations of very long chain acylcarnitine(VLCAC) and lysophosphatidylcholine(LPC),and to evaluate the diagnostic efficiency of VLCAC and LPC in the diagnosis of X-linked adrenoleukodystrophy(X-ALD). Methods A total of 3 530 samples of dried blood spots for screening genetic metabolic diseases and 10 samples of dried blood spots from children with X-ALD were collected. VLCAC and LPC were extracted from dried blood spots by solvent extraction with standard substances containing stable isotopic markers of 2H3-hexacosanoylcarnitine(2H3-C26) and 2H4-C26:0 lysophosphatidylcholine(2H4-C26:0-LPC) direct injection in tandem mass spectrometer. Eicosanoylcarnitine(C20), docosanoylcarnitine(C22), tetracosanoylcarnitine(C24), hexacosanoylcarnitine(C26), C20:0 lysophosphatidylcholine(C20:0-LPC), C22:0 lysophosphatidylcholine(C22:0-LPC), C24:0 lysophosphatidylcholine(C24:0-LPC) and C26:0 lysophosphatidylcholine(C26:0-LPC) were detected. Methodological evaluation (precision,accuracy and linearity) of the established MS/MS was performed. Partial least square method was used to analyze the contribution of each index to disease. Receiver operating characteristic(ROC)curve was used to evaluate the efficiency of each index for the diagnosis of X-ALD. Results The within-run coefficients of variation(CV) of low-concentration C26 and C26:0-LPC were 4.16% and 7.75%,and the between-run CV were 8.29% and 9.17%,respectively. The within-run CV of high-concentration C26 and C26:0-LPC were 5.57% and 8.68%,and the between-run CV were 7.45% and 8.11%,respectively. The accuracies were 93.25%-104.94%. The determination coefficients(r2) between the measured values of different dilution concentrations and the theoretical concentration were 0.996 and 0.994. Except for C20,C24:0-LPC/C20:0-LPC,C24:0-LPC/C22:0-LPC and C26:0-LPC/C20:0-LPC,the difference between control group and X-ALD group was statistically significant(P<0.05). C26,C26/C22 ratio and C26:0-LPC had the highest contribution to disease(the partial regression coefficients were 0.175 3,0.130 0 and 0.079 2,respectively). ROC curve analysis showed that the sensitivity and specificity of the ratios of C26 and C26/C22 in diagnosing X-ALD were all 100%,and the area under curve(AUC) was 1.0. The sensitivity,specificity and AUC of C26:0-LPC were 100%,72.9% and 0.972,respectively. Conclusions Non-derivatized MS/MS has high precision and accuracy in detecting VLCAC and LPC. C26 may be a diagnostic marker of X-ALD.

Key words: Very long chain acylcarnitine, Lysophosphatidylcholine, Tandem mass spectrometry, X-linked adrenoleukodystrophy

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