Table 2.

Application and progress of tandem mass spectrometry in recent 5 years

Researcher/ Year/ref	Sample	Characteristics	Result	Significance
Auray-Blais et al. [4]	Urine-GAG	Analyzed KS disaccharides and creatinine	All MPSI VA patients showed abnormal results before treatment compared to reference values	A good way to differentiate between MPS IVA patients and normal population
Khan et al. [40]	Urine/hematology -GAG	Assessed blood GAGs in MPS II, III, IVA and IVB, and urine GAGs in MPS IVA, IVB and VI by LC‒MS /MS	Helpful for diagnose MPSs, urinary KS is not a useful biomarker for monitoring the effectiveness of MPS IVA treatment	LC‒MS /MS can be used to track treatment effects
Tanaka et al. [76]	Brain/CSF -GAG	Quantified HS and DS in low volume samples by combining acid methanolysis and LC‒MS /MS	HS, but not DS, accumulated in the CNS. HS levels in CSF correlated with that in the brain	CSF HS Levels may be a useful biomarker for cerebral GAGs accumulation and drug efficacy in MPS II
Tebani et al. [78]	/	Targeted and untargeted metabolomics based on ultraperformance LC‒MS /MS	Major amino acid pathway impairments in MPS III, mainly arginine-proline metabolism and urea cycle metabolism	The first metabolomics-based study of MPS III and helps to elucidate the pathophysiology of MPS III.
Lin et al. [47]	Urine-GAG	Analyzing the urinary GAGs phenotype and levels among different types of MPSs by LC‒MS /MS	Different GAGs help predict phenotypes. GAG-graded biomarkers is more sensitive and reliable than DMB ratio	MS/MS can to predict phenotypes with high sensitivity
Tebani et al. [79]	/	Nontargeted metabolomics analysis	Several major amino acid pathways (arginine-proline, histidine and glutathione) are dysregulated in MPS VI	One of the first metabolic phenotyping studies of MPS VI; helpful for understanding the molecular pathophysiology of MPS
Chan et al. [18]	DBS-enzyme		Additional molecular analysis of patientss with low enzyme activity	MS/MS for MPS I, II and VI enzyme analysis for newborn screening
Saville et al. [67]	Urine-GAG	Measuring specific GAGs fragments of terminal residues associated with genetic defects	This method provides 100% specificity and sensitivity	This new urine test can diagnose 10 mucopolysaccharidosis subtypes in a single test and enables longitudinal biochemical monitoring after therapeutic interventions
Lin et al. (Lin, Lo, et al [48]). ,	Urine-GAG	Calculating GAG-derived disaccharide levels based on the amount (peak area) of CS	CS normalization produces more consistent values than creatinine normalization	The use of CS standardized suspicion reveals the actual status of DS, HS and KS
Makower et al. [51]	Brain/CSF -GAG	Determination of HS metabolites and HS digests after heparinase treatment	The relative reduction of HS in the brain of MPS IIIA mice after administration was similar, and this reduction was also reflected in the CSF	HS digests can be used in clinical studies to determine HS levels in CSF of MPS IIIA patients
Taylor et al. [77]	DBS-enzyme	Adoption of a secondary screening methodology and incorporation of a collaborative laboratory synthesis report	Discovery of pseudodeficient alleles and variants of unknown significance	Need for secondary testing to reduce follow-up burden
Kadali et al. [37]	Urine-GAG	Qualitatively and quantitatively analyzed GAGs, and perform specific enzyme analysis to confirm the diagnosis	The accuracy of the categorical regression tree model in the differential diagnosis of MPS was 96.3% and 98.3%, respectively. Thresholds for different GAGs to diagnose specific MPS types were established	Can be used for early decision making and disease diagnosis
Lin et al. (Lin, Lee, et al [46]). ,	Urine-GAG	Qualitative and quantitative analysis of GAGs with specific enzyme analysis and targeted gene sequencing to confirm diagnosis	No false-negative results for urinary DS, HS and KS using MS/MS-based methods	Established a platform for interprofessional collaboration based on risk criteria to allow for early confirmation of the diagnosis of MPSs
Burton et al. [17]	DBS-enzyme	MS/MS for measuring IDS activity in DBS	Discovery of 1 MPS II and 14 IDS pseudodeficient infants	Suggests MPS II could be included in Illinois newborn screening program
Menkovic et al. [56]	Urine-GAG	Evaporation of eluted urine samples from 21-day-old neonates with methanolysis reaction	Method validation showed high precision and accuracy for all analytes	A rapid and effective method for population-based neonatal urine screening using MS/MS is presented
Scott et al. [70]	DBS-enzyme	Analysis of five enzyme activities by a 5- plex method	The number of initial screen-positive samples using this method is low and manageable	Population-based newborn screening for related diseases is feasible
Chien et al. [20]	DBS-enzyme	8-fold analysis of 8 LSDs including MPS I, II, IIIB, IVA, VI	8-plex LSD screening test enables routine newborn screening for MPS IVA and other LSDs	Further validation of MS/MS for enzyme multiplex analysis
Wang et al. [90]	GAG	Development of high-throughput enzyme digestion assays	The method is highly sensitive	GAGs in CSF can be used as brain GAGs replacement biomarker, and this analysis can be used in future studies and applications to assess the feasibility of enzyme therapeutic effects in a variety of MPSs
Khaledi et al. [38]	DBS-enzyme	Incubation of enzyme-specific substrates with dried blood spots or fibroblast lysates	The test allows newborns to be screened and diagnosed for all MPSs except the extremely rare MPS-IX	First multiplexed assay for 10 enzyme activities in DBS and fibroblast lysates
Zhang et al. [93]	Bllod/urine/CSF-GAG	Methanolization of DS, HS, CS in serum/plasma, urine and cerebrospinal fluid to dimers	DS and HS in urine and CSF are more sensitive biomarkers for monitoring ERT therapy in MPS I patients compared to serum GAGs	Urine and CSF better for detecting disease progression
Chuang et al. [22]	Urine-GAG	Calculation of urinary DS, HS, and KS using the CS-standardized method rather than the traditional creatinine-standardized method	MS/MS-based analysis of GAG-derived disaccharides is feasible and reliable	Confirmation of the diagnosis of MPS requires quantification of GAG-derived disaccharides, and analysis of genetic variants can help predict outcome and guide treatment
Zhang et al. [92]	/	Synovial fluid and serum samples were collected from 12-month-old MPS I and healthy dogs and protein abundance was characterized using MS/MS	Elevated expression of matrix metalloproteinase 19, alpha-trypsin interrepressor heavy chain 3, and alpha-1-microglobulin confirmed in MPS I cartilage	Candidate biomarkers have potential to improve patient care
Courtney et al. [23]	DBS-enzyme	Cold-induced aqueous acetonitrile phase separation was investigated to improve the combination of 6-plex and IDS extracts	This method improves the detection of IDS products without significant impairment of other analytes	Creating a stable and time-consuming 7-plex analysis methodology

tandem mass spectrometry (MS/MS); mucopolysaccharidoses (MPSs); lysosomal storage diseases (LSDs); iduronate-2-sulfatase (IDS); glycosaminoglycan (GAG); keratan sulfate (KS); cerebrospinal fluid (CSF); heparin sulfate (HS); dermatan sulfate (DS); dimethyl methylene blue (DMB); enzyme replacement therapy (ERT); chondroitin sulfate (CS); liquid chromatography tandem mass spectrometry (LC‒MS/MS); glycosaminoglycans (GAGs); mucopolysaccharidose (MPS)