ParameterGC/MSMS/MS

Newborn specimen collected

Urine:
  • Contains more than 3,000 detectable metabolites, with many in higher concentration than in blood
  • Non-invasive, safe, and simple for collection by parents or hospital staff
Blood:
  • Though contains similar number of detectable metabolites as urine, many not in as high concentration than in urine
  • Invasive, painful, requires technical expertise, risk of infection
  • Certain metabolic disoreders do not alter blood amino acid or acylcarnitine profile, hence further testing is required to differentiate type o disorder
No. of metabolic disorders ("IEMs")that can be detected and quantified 100+ IEMs from 9 groups of IEMs
  • Amino acidemia
  • Organic acidemia
  • Disorders of fatty acid metabolism
  • Disorders of sugar metabolism
  • Urea cycle disorders
  • Lactate, pyruvate + TCA cycle abnormalities
  • Purine, pyrimidine disorders
  • Peroxisomal disorders
40+ IEMs from 3 groups of IEMs
  • Amino acidemia
  • Organic acidemia
  • Disorders of fatty acid metabolism
Biomarker, i.e. no. of analyte profiles used Multiple markers used:
Highly specific, definitive interpretation from one single test
Mostly single marker used:
Non-specific, ambiguous – 2nd tier testing required
Time to diagnosis Faster:
From screening-cum-confirmation to diagnosis
Slower:
From screening to confirmation then finally to diagnosis
Further confirmation required Screening and confirmation from one single test, though occasionally requires further confirmation via:
  • Enzyme assays
  • Genetic testing
Requires confirmatory test via:
  • GC/MS analysis
  • Enzyme assays
  • Genetic testing
Throughput Approximately 15 minutes per sample:
Total throughput of about 60 – 90 samples per machine in one day
Approximately 2 minutes per sample:
Total throughput of about 500 samples per machine in one day thus better for mass screening
Interference
  • Chromatography separates potential interfering compounds, such as drugs and exogenous chemicals
  • Acylcarnitine profiling not critical in GC/MS urinary analysis
Certain drugs and exogenous chemicals can interfere with acylcarnitine profile analysis e.g. valproic acid, cefotaxime, dextrose