Method for interpreting tandem mass spectrometry data for clinical diagnosis of genetic disorders such as hypermethionemia

• US 20060025933A1
• Filed: 09/20/2005
• Published: 02/02/2006
• Est. Priority Date: 01/30/1999
• Status: Active Grant

• Current Assignee: PerkinElmer Genetics, Inc. (Revvity, Inc.)
• Original Assignee: Pediatrix Screening Inc (Revvity, Inc.)
• Inventors: Chace, Donald H.
• Granted Patent: US 7,244,621 B2
• Time in Patent Office: Days
• US Class Current: 702/22
• CPC Class Codes: C12Q 1/32 involving dehydrogenase
• CPC Class Codes: G01N 2800/02 Nutritional disorders
• CPC Class Codes: G01N 33/6815 containing sulfur, e.g. cysteine, cystine, methionine, homocysteine
• CPC Class Codes: G01N 33/6848 Methods of protein analysis involving mass spectrometry
• CPC Class Codes: G01N 33/6893 related to diseases not provided for elsewhere
• CPC Class Codes: G01N 33/92 involving lipids, e.g. cholesterol , lipoproteins, or their receptors steroid hormones G01N33/743
• CPC Class Codes: H01J 49/0036 Step by step routines describing the handling of the data generated during a measurement
• CPC Class Codes: Y10T 436/24 Nuclear magnetic resonance, electron spin resonance or other spin effects or mass spectrometry

Abstract

A method for interpreting data that is produced after a group of amino acids and acylcarnitines are derivatized from blood spots taken from newborn babies and scanned by a tandem mass spectrometer. Concentration levels of each metabolite, which are directly proportional to the butyl ester fragment after derivatization, are compared to threshold flags for determining a significance of any deviation of the metabolite relative to the flag threshold. The threshold flags are diagnostic limits to the data retrieved from each blood spot. The data includes metabolite concentrations and molar ratios of metabolites with other metabolites. Samples are labeled normal for a disease if the concentration of any of the metabolite concentrations or molar ratio concentration do not deviate from the flag threshold, but, in contrast, the sample must be further evaluated if a value is elevated or deficient to some degree. Thus, as each metabolite fragments at a different mass to charge value (m/z), corresponding data is compared to the respective flag thresholds for determining a next course of action that must be taken to ultimately assist a physician in the diagnosis of a genetic disorder such as hypermethionemia resulting from an elevation or deficiency of the metabolite particular for that disorder.

Claims

1. A method comprising steps of:

acquiring mass spectral data from a sample that has been derived from the blood of a patient, wherein said data includes values comprised of a methionine concentration (met) and optionally a molar ratio of methionine concentration (met) and optionally a molar ration of methionine and phenylalanine (met/phe);

comparing said values, respectively, with a met flag threshold and optionally a met/phe flag threshold;

identifying whether or not there is an elevation of any of said values above any of said flag thresholds; and

interpreting said sample as being normal for hypermethionemia, provided there is no said elevation of any of said values.

2. The method of claim 1, wherein:

in the acquiring step, said data includes values comprised of a methionine concentration (met) and a molar ratio of methionine and phenylalanine (met/phe); and

in the comparing step, said met and met/phe are compared with a met flag threshold and a met/phe flag threshold, respectively.

3. The method of claim 1 further comprising:

flagging the sample for re-analysis provided any of the following occur;

i. said met is greater than said met flag threshold;

or

ii. said met is greater than about 50 μ

M and said met/phe is greater than said met/phe flag threshold.

4. The method of claim 3 further comprising:

performing a re-analysis of said sample or a new sample from the same patient to obtain mean values.

5. The method of claim 4 further comprising:

initiating a follow-up protocol based on follow-up criteria utilizing said mean values.

6. The method of claim 1 further comprising:

flagging the sample for re-analysis provided any of the following occur;

i. said met is greater than about 150 μ

M;

or

ii. said met is greater than about 125 μ

M and said met/phe is greater than about 1.25.

7. The method of claim 6 further comprising:

performing a re-analysis of said sample or a new sample from the same patient to obtain mean values.

8. The method of claim 7 further comprising:

initiating a follow-up protocol based on follow-up criteria utilizing said mean values.

9. The method of claim 1, wherein said met flag threshold and said met/phe flag threshold are, respectively, about 31 μ

M and about 0.54.

10. The method of claim 1, wherein said met flag threshold and said met/phe flag threshold are, respectively at least about 41 μ

M and 0.69.

11. The method of claim 1, wherein said met flag threshold and said met/phe flag threshold are, respectively, about 60 μ

M and 1.0.

12. The method of claim 5, wherein the sample were derived from a dry blood spot on filter paper.

13. The method of claim 12, wherein the sample were derivatized.

14. The method of claim 1, wherein:

in the acquiring step, said data was acquired using a tandem mass spectrometer.