A rapid and efficient method to screen newborns or people at risk for adrenoleukodystrophy (ALD) in India has been developed, according to a new study.
The study, “Flow injection ionization-tandem mass spectrometry-based estimation of a panel of lysophosphatidylcholines in dried blood spots for screening of X-linked adrenoleukodystrophy,” was published in the journal Clinica Chimica Acta.
ALD is a genetic disorder caused by mutations in the ABCD1 gene that lead to the accumulation of fatty molecules known as very long-chain fatty acids (VLCFA). Abnormally high levels of these fats in the body can destroy myelin — the fatty substance that protects nerve cells — and damage adrenal glands (small hormone-producing glands that are located above the kidneys).
If a person shows symptoms of ALD, a diagnostic blood test is performed to determine the level of VLCFAs and estimate the severity of the disease. The long-chain fatty acids identified in the test are C26:0, C24:0, and C22:0. Fatty acids are named for the number of carbon atoms and unsaturated bonds. For example, the fatty acid C26:0 is 26 carbons atoms long, and has no unsaturated bonds (making it a saturated fatty acid).
The accumulation of VLCFAs also triggers the build-up of related molecules called 26:0-lysophosphatidylcholine (LPC) and 24:0-LPC. These molecules have recently been identified as sensitive and specific markers for ALD, and can be rapidly detected in dried blood spots using a method called flow injection ionization-tandem mass spectrometry, or FIA-MS/MS.
As such, the FIA-MS/MS method to screen newborns for ALD has been implemented in the U.S.
However, in India, newborn screening for ALD has not yet been added to the national health program. While older, slower LPC detection methods have been successfully used to diagnose ALD in the country, there is a need to develop a rapid method to screen a larger population.
Therefore, a team of researchers at the National Institute of Mental Health and Neurosciences, in Bengaluru, India, developed a faster, more efficient (high-throughput) method to screen a series of LPCs — namely C26:0-LPC, C24:0-LPC, C22:0-LPC, and C20:0-LPC — in dried blood spots through FIA-MS/MS.
To show the accuracy and precision of this method, known amounts of LPCs were added to some dried blood spots and tested. Results showed the FIA-MS/MS method detected similar amounts of LPCs in samples with known amounts.
The team also tested samples with known amounts of LPCs sent by the Centers for Disease Control and Prevention under its Newborn Screening Quality Assurance Program. The amounts detected also matched CDC controls.
To confirm the method as an ALD diagnostic tool, LPC levels in dried blood spots from 28 ALD patients were compared to those from 282 healthy individuals (control group). Using automated methods, FIA-MS/MS was applied to estimate the amount of LPCs in each sample.
Results showed the level of C26:0-LPC from ALD patients was six times higher, and their C24:0-LPC level was three times higher than samples from healthy controls.
Significantly higher ratios of C26:0/C22:0 and C24:0/C22:0 — important markers for ALD diagnosis — were detected in the ALD samples as well.
These results were then compared to an older method for LPC detection called liquid chromatography-tandem mass spectrometry (LC-MS/MS). This test found that the amounts of LPCs detected by FIA-MS/MS were similar but slightly higher than those detected by LC-MS/MS.
“The FIA-MS/MS method showed good concordance with the LC-MS/MS method,” the researchers wrote.
Overall, “for the first time in India, we were able to successfully develop a high-throughput, FIA-MS/MS method for estimating a panel of LPCs in [dried blood spots] with a sample run time of 1.5 min,” the researchers said.
“This high-throughput and rapid method can be used for mass screening of newborns or high-risk cases for X-ALD in the Indian population in whom genetic disorders could be highly prevalent as parental consanguinity is common,” the team added.
