MS/MS APPROACHES TO CLINICAL TESTING FOR INBORN ERRORS OF METABOLISM

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1 MS/MS APPROACHES TO CLINICAL TESTING FOR INBORN ERRORS OF METABOLISM Tina M. Cowan, PhD Director, Clinical Biochemical Genetics Laboratory Stanford University Medical Center

2 Presented at the 2011 Stanford Mass Spectrometry Users Meeting For personal use only. Please do not reuse or reproduce without the author s permission. 1

3 Metabolic Pathways

4 Inborn Errors of Metabolism S 3 S 1 S 2 Substrate mutant enzyme Product P 1 P 2

5 The Triple Quadrupole Tandem Mass Spectrometer Ion Source MS1 Collision MS2 Detector Cell

6 Inborn Errors Of Metabolism HPLC/ spectrophotometry GC/MS MS/MS Enzyme assays Amino acids PKU, MSUD, Urea cycle defects Organic acids Methylmalonic acidemia, propionic acidemia Fatty acids MCAD, VLCAD Organelles Lysosomal storage diseases Mitochondrial myopathies Perixosomal disorders

7 PKU: An Inherited Disorder of Phenylalanine Metabolism

8 Neutral loss (m/z 102)

9 Acylcarnitine Profile: precursors of m/z 85 I n t e n s i t y, c p s +Precursor (85.0): 28 MCA scans from Sample 6 (H38870 Asa-Nunies, W) of Data wiff 1.5e6 1.4e6 1.3e6 1.2e6 1.1e6 1.0e6 9.0e5 8.0e5 7.0e5 6.0e C0 C0-d C = C16-d3 Max. 1.5e6 cps. RC- O + O (CH 3 ) 3 N-CH 2 -CH-CH 2 -COO - = 5.0e5 C2-d3 C5-d9 4.0e5 C14-d C4-d C10-d e5 C8-d e5 C3-d e m/z, amu O 459.7

10 Acylcarnitine Profile: precursors of m/z 85 Medium-Chain Acyl-CoA Dehydrogenase (MCAD) Deficiency

11 Evolution of Clinical Testing by MS/MS Amino Acids (limited panel) Acylcarnitine Profile Single analyte determinations Methylmalonic acid Orotic acid S-Sulfocysteine Guanadinoacetate/creatinine Succinylacetone Carnitine Many more Immunosuppressive drugs (e.g., mycophenolic acid) Steroid hormones Vitamin D

12 Testing in the Clinical Laboratory Elements of Method Validation Accuracy Precision Linearity Analytic measurement range LLOD, LLOQ Recovery or correlation with existing method

13 Amino Acid Analysis

14 Amino Acid Chromatogram

15 Amino Acid Analysis by MS/MS: Challenges Separation of isomers (leu, ileu, alloileu) Chromatographic removal of salts Availability of standards Derivatization Ion suppression Sensitivity Imprecision

16 Tony Le, Stanford Biochemical Genetics Laboratory

17 Amino Acid Analysis: Methods 1. Plasma, urine, CSF 2. Deproteinize with 6% sulfosalicylic acid (1:1) 3. Incubate at room temperature, 5min 4. Centrifuge at 13,000rpm, 5min 5. Dilute 10µL of supernatant with 800µL of 2mM tridecafluoroheptanoic acid (TDFHA) containing internal standards glucosaminic acid and s-2- aminoethyl cysteine 6. Transfer to autosampler vials

18 Column 1: Porous graphitic carbon (PGC) (3µm Hypercarb, 4.6mm ID x 50mm) 1mM TDFHA in water Separation of negatively charged salts from first-eluting amino acid

19 Flow-Reversal of Column 1

20 Column 2: Fused-core (2.7µm Halo C18, 2.1mm IDx 100mm), 50ºC

21 Baseline resolution of leucine isomers (m/z 132.1>86.1) Leucine Isoleucine Alloisoleucine

22 Baseline resolution of sarc and ala (m/z 90.0>44.2) Sarcosine Alanine β- Alanine

23 Amino Acid Analysis, 50 nmol standard Pro (116>70) Orn (118>72) Phe (166>120) Gln (147>84) Val (118>72) Alloileu Ileu Leu

24 Amino Acid Analysis, MSUD plasma

25 Urine Amino Acid Analysis LC-MS/MS HPLC + Ninhydrin

26 Glycine 10 nmol/ml

27 Adding other compounds: S-adenosylmethionine/S-adenosylhomocysteine

28 Lessons Learned Along the Way Sample preparation matters Ion suppression where you least expect it Choice of calibration material Choice of internal standards

29 Not All Sample Preps Are Created Equal

30 Plasma Prep 1: Methanol:Acetonitrile (3:1) R 2 = Alanine 800 MS/MS ,000 Biochrom 30

31 Plasma Prep 2: 6% SSA in H 2 O R 2 = Alanine MS/MS Biochrom 30

32 Ion Suppression Where You Least Expect It Or: Calibration Matters

33 15 N- 13 C-Glycine Response at Varying Glycine Concentrations 100 nmol gly 1000 nmol gly

34 2 H 4 -Alanine Response at Varying Alanine Concentrations 10 nmol ala 2000 nmol ala

35 S-aminoethyl-cysteine response at varying amino acid concentrations

36 The Standard Curve

37 Curve fit: 1/x 2 Isoleucine

38 Curve fit: 1/x 2 Arginine

39 Curve fit: 1/x Arginine

40 Lysosomal Enzyme Testing by MS/MS Gaucher disease Inherited deficiency of β-glucocerebrosidase Abnormal accumulation of lipids Enzyme replacement therapy Candidate for newborn screening?

41 Gaucher Disease Testing substrate product

42 Gaucher Disease Testing: Results I.S. Substrate Product (482>264)

43 Other Lysosomal Enzymes Krabbe disease Niemann-Pick A&B

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45 MS/MS in the Clincial Lab: Ongoing challenges Sample prep Choice of standards Chromatographic conditions Ease of operator use Software Clinical lab workflow Peak review Report generation, interface

46 Thanks to.. Tony Le Angie Ng Tony Kway Kristina Cusmano-Ozog