Liquid chromatography-tandem mass spectrometry method for estimation of a panel of lysophosphatidylcholines in dried blood spots for screening of X-linked adrenoleukodystrophy

A pilot study of newborn screening for X-linked adrenoleukodystrophy based on liquid chromatography-tandem mass spectrometry method for detection of C26:0-lysophosphatidylcholine in dried blood spots: Results from 43,653 newborns in a southern Chinese population

BACKGROUND

X-linked adrenoleukodystrophy (X-ALD) is a rare X-linked disease caused by mutations of the ABCD1 gene. C26:0-lysophosphatidylcholine (C26:0-LPC) has been proved to be an accurate biomarker for X-ALD. This study aims to propose an effective method for screening of X-ALD and to evaluate the performance of the newborn screening (NBS) assay for X-ALD in Guangzhou.

METHODS

C26:0-LPC in dried blood spots (DBS) was extracted by methanol solution containing isotope-labelled internal standard (C26:0-d4-LPC) and analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The sensitivity of the method was assessed in eight male X-ALD patients, two female carriers and 583 healthy controls. The method was conducted on 43,653 newborns. Next generation sequencing was performed on screen-positive samples. Plasma analysis of very long-chain fatty acids and genetic counselling were performed by way of follow-up.

RESULTS

Elevated C26:0-LPC were 100% sensitive for screening of X-ALD. Of 43,653 newborns, 32 (18 males, 14 females) screened positive. Of these, 14 (43.7%) were identified ABCD1 variants, including seven hemizygous males and seven heterozygous females, and two (6.3%) were diagnosed with other peroxisomal disorders.

CONCLUSION

The LC-MS/MS method for screening of X-ALD can identify males, heterozygous females and other peroxisomal disorders. The incidence of X-ALD in Guangzhou is not low.

Age and gender-specific reference intervals for a panel of lysophosphatidylcholines estimated by tandem mass spectrometry in dried blood spots

Background and objectives

Very long-chain fatty acyl-lysophosphatidylcholines (VLCFA-LysoPCs) are measured in dried blood spots (DBS) for identifying X-linked adrenoleukodystrophy (X-ALD) and other inherited peroxisomal disorders. Our study aimed to establish age- and gender-specific reference intervals for a panel of LysoPCs measured by tandem mass spectrometry in DBS.

Methods

LysoPCs (26:0-, 24:0-, 22:0- and 20:0-LysoPCs) were estimated by flow injection analysis-tandem mass spectrometry (FIA-MS/MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods in 3.2 mm blood spots of 2689 anonymized, putative normal subjects (1375 males, and 1314 females) aged between 2 days and 65 years. Samples were divided into groups: Neonates (0-1month), Infants (>1m-1year), Children and Adolescents (>1-18years), and Adults (>18years). Reference intervals were determined using the percentile approach and represented as the median with the 1^st and 99^th percentile lower and upper limits.

Results

The percentage coefficient of variation (CV) for repeatability assays of internal and external quality control samples were within acceptable limits. Significant differences (P <0.0001, P <0.01) were observed in the concentrations of 26:0-, 24:0-, 22:0- and 20:0-LysoPCs and their ratios, 26:0/22:0-, 24:0/22:0-, 26:0/20:0-and 24:0/20:0-LysoPC in neonates and infants when compared to children, adolescents, and adults. Levels of 26:0-, 24:0- and 22:0-LysoPCs decreased, whereas 20:0-LysoPC increased with age. There were no significant gender-based differences in the concentration of LysoPCs.

Conclusion

We established age- and gender-specific reference intervals for a panel of LysoPCs in DBS. These reference values would be helpful when interpreting LysoPC values in DBS during screening for X-ALD and other peroxisomal disorders.

Photoacoustic identification of blood authenticity based on quantum-behaved particle swarm optimized wavelet neural network

To accurately identify the blood authenticity, a set of photoacoustic detection system was established. In experiments, five kinds of blood in total of 125 groups were used, the time-resolved photoacoustic signals and peak-to-peak spectra were obtained in 700 to 1064 nm. Experimental results showed the accurate identification of blood authenticity was limited due to overlap of signals and spectra. To solve the problem, wavelet neural network (WNN) was employed to supervised train peak-to-peak spectra of 100 samples. The correct rate was 72% for 25 test samples. To improve correct rate, the parameters of WNN were optimized by quantum-behaved particle swarm optimization (QPSO) algorithm. Meanwhile, the effects of neurons number, learning rate factors, iteration times and training times on correct rate were studied and compared with WNN and WNN-PSO algorithms. Results showed the correct rate of WNN-QPSO was increased to 96%. Then, three kinds of dynamic contraction-expansion coefficients were used. Under the optimal dynamic coefficient, the correct rate reached 100%. Moreover, the truncated mean stabilization strategy (TMSS) was coupled to improve the convergent speed. Finally, 10 algorithms were compared. Results demonstrated that photoacoustic spectroscopy combined with WNN-QPSO coupled with TMSS and dynamic contraction-expansion coefficient had an excellent performance in the identification of blood authenticity.

Classification and discrimination of real and fake blood based on photoacoustic spectroscopy combined with particle swarm optimized wavelet neural networks

In this work, photoacoustic spectroscopy was employed to distinguish real blood from fake blood rapidly, accurately, and recoverably. To achieve this goal, a photoacoustic detection system for blood was established in the forward mode. In the experiments, four kinds of animal blood and two kinds of fake blood in a total of 150 groups were used. The time-resolved photoacoustic signal and peak-to-peak values (PPVs) of all blood were captured in 700-1064 nm with intervals of 5 nm. Experimental results show that the amplitudes, profiles, peak-point time, and PPVs are different between real and fake blood. Although the PPVs of real blood are larger than those of the fake ones at 700-850 nm, the differences in PPVs are not obvious at 850-1064 nm, especially when there are spectral overlaps of PPVs. To accurately classify and discriminate real and fake blood, a wavelet neural network (WNN) was used to train 120 groups of blood and test 30 groups of blood. Moreover, the particle swarm optimization (PSO) algorithm was used to optimize the weights and thresholds, as well as the translation and scale factors of the Morlet-liked wavelet basis function of the WNN. Under optimal parameters, the correct rate of the WNN-PSO algorithm was improved from 63.3% to 96.7%. Next, principal component analysis (PCA) was combined into the WNN-PSO algorithm to further improve the correct rate. The results indicate that the correct rate of the PCA-WNN-PSO algorithm with 10 principal components reaches 100 %. Therefore, photoacoustic spectroscopy combined with the PCA-WNN-PSO algorithm exhibits excellent performance in the classification and discrimination of real and fake blood.

Utility of measuring very long-chain fatty-acyl carnitines in dried blood spots for newborn screening of X-linked Adrenoleukodystrophy

We measured C24:0 and C26:0-carnitines in dried blood spots by flow injection analysis-tandem mass spectrometry method to evaluate whether they can be used as markers for newborn screening of X-linked Adrenoleukodystrophy (X-ALD). We found that C26:0-carnitine was 95.1% and 44.7% sensitive for identifying male X-ALD cases and heterozygous females, respectively. False negatives were found for C24:0-carnitine (11/82) and C26:0-carnitine (4/82). We conclude that C24:0 and C26:0-carnitines may not be reliable markers for X-ALD screening.

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C24:0, C26:0-carnitines were measured in DBS of confirmed X-ALD cases

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Sensitivity of C26:0-carnitine was 95.1% for X-ALD males, 44.7% for heterozygous females

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False negatives were found for C24:0-carnitine (11/82) and C26:0-carnitine (4/82)

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C24:0, C26:0-carnitines are not reliable markers for X-ALD screening

Flow injection ionization-tandem mass spectrometry-based estimation of a panel of lysophosphatidylcholines in dried blood spots for screening of X-linked adrenoleukodystrophy

BACKGROUND

Elevated blood C26:0 lysophosphatidylcholine (LPC) is a diagnostic marker for X-linked adrenoleukodystrophy (X-ALD). Our aim was to develop a flow injection ionization-tandem mass spectrometry (FIA-MS/MS) method for estimating a panel of LPCs (C20:0-C26:0-LPCs) in dried blood spots (DBS) and to determine the sensitivity and specificity of this method for high-throughput screening for X-ALD.

METHODS

LPCs (C20:0-C26:0) were extracted from 3.2 mm DBS in a 96-well plate, spiked with isotopically-labelled internal standard (C26:0-d4-LPC) and measured by FIA-MS/MS in electrospray ionization (ESI)-positive, multiple reaction monitoring (MRM) mode using a triple quadrupole, tandem mass spectrometer. The sensitivity and specificity of the FIA-MS/MS method for screening of X-ALD was determined. The FIA-MS/MS method was compared with the LC-MS/MS method for estimating LPC concentrations.

RESULTS

Elevated C26:0 and C24:0-LPCs were 100% sensitive for identification of X-ALD. However, specificity was only 78.33% for C26:0 and 98.33% for C24:0-LPCs. Sensitivity for C22:0 and C20:0 LPCs were 89.29%, 78.33% and specificity, 67.86% and 73.33%, respectively. The FIA-MS/MS method showed good concordance with the LC-MS/MS method.

CONCLUSION

The FIA-MS/MS method for estimating C26:0 and C24:0-LPCs in DBS is suitable for first-tier screening of newborns for X-ALD. Second-tier confirmatory testing is required to screen positive cases.