Methods and systems for determining autism spectrum disorder risk
In certain embodiments, the invention stems from the discovery that analysis of population distribution curves of metabolite levels in blood can be used to facilitate predicting risk of autism spectrum disorder (ASD) and/or to differentiate between ASD and non-ASD developmental delay (DD) in a subject. In certain aspects, information from assessment of the presence, absence, and/or direction (upper or lower) of a tail effect in a metabolite distribution curve is utilized to predict risk of ASD and/or to differentiate between ASD and DD.
1. A method comprising steps of:
(i) obtaining a first set of blood samples from human subjects having autism spectrum disorder (ASD) and a second set of blood samples from human subjects having non-ASD developmental delay (DD);
(ii) measuring levels of metabolites in the first and second set of samples,
wherein the metabolites comprise xanthine, gamma-CEHC, hydroxy-chlorothalonil, 5-hydroxyindoleacetate (5-HIAA), indoleacetate, p-cresol sulfate, 1,5-anhydroglucitol (1,5-AG), 3-(3-hydroxyphenyl)propionate, 3-carboxy-4-methyl-5-propyl-2-furanpropanoate (CMPF), 3-indoxyl sulfate, 4-ethylphenyl sulfate, 8-hydroxyoctanoate, hydroxyisovaleroylcarnitine (C5), isovalerylglycine, lactate, N1-Methyl-2-pyridone-5-carboxamide, pantothenate (Vitamin B5), phenylacetylglutamine, pipecolate, 3-hydroxyhippurate, and octenoylcarnitine;
(iii) determining a distribution profile for the metabolites in the first set and second set of samples, wherein the distribution profile has a lower end and an upper end;
(iv) defining for each metabolite:
(a) a first threshold at the lower end of the distribution profile (left tail), wherein the first threshold is the 15 th percentile; and
(b) a second threshold at the upper end of the distribution profile (right tail), wherein the second threshold is the 90 th percentile.
2. The method of claim 1 , wherein the blood samples are plasma samples.
3. The method of claim 1 , wherein the metabolite levels are measured by mass spectrometry.
4. A method of differentiating between autism spectrum disorder (ASD) and non-ASD developmental delay (DD) in a human subject, the method comprising steps of:
(i) measuring the levels of a plurality of metabolites in a blood sample obtained from the subject, wherein the plurality of metabolites comprises at least two metabolites selected from the group consisting of xanthine, gamma-CEHC, hydroxy-chlorothalonil, 5-hydroxyindoleacetate (5-HIAA), indoleacetate, p-cresol sulfate, 1,5-anhydroglucitol (1,5-AG), 3-(3-hydroxyphenyl)propionate, 3-carboxy-4-methyl-5-propyl-2-furanpropanoate (CMPF), 3-indoxyl sulfate, 4-ethylphenyl sulfate, 8-hydroxyoctanoate, hydroxyisovaleroylcarnitine (C5), isovalerylglycine, lactate, N1-Methyl-2-pyridone-5-carboxamide, pantothenate (Vitamin B5), phenylacetylglutamine, pipecolate, 3-hydroxyhippurate, and octenoylcarnitine;
(ii) calculating the number of metabolites measured in step (i) selected from 3-carboxy-4-methyl-5-propyl-2-furanpropanoate (CMPF), 3-indoxyl sulfate, 4-ethylphenyl sulfate, 8-hydroxyoctanoate, gamma-CEHC, hydroxyisovaleroylcarnitine (C5), indoleacetate, isovalerylglycine, N1-Methyl-2-pyridone-5-carboxamide, p-cresol sulfate, phenylacetylglutamine, octenoylcarnitine, and 1,5-anhydroglucitol (1,5-AG) with a level in the sample at or below the lower threshold as defined in step (iv) of claim 1 (ASD left tail);
(iii) calculating the number of metabolites measured in step (i) selected from 5-hydroxyindoleacetate, lactate, pantothenate (Vitamin B5), pipecolate, xanthine, and hydroxy-chlorothalonil with a level in the sample at or above the upper threshold as defined in step (iv) of claim 1 (ASD right tail);
wherein a higher number of metabolites calculated in (ii) and (iii) is indicative of a higher likelihood that a subject as ASD;
(iv) calculating the number of metabolites measured in step (i) selected from 3-(3-hydroxyphenyl)propionate, pipecolate, xanthine, and 3-hydroxyhippurate with a level in the sample at or below the lower threshold as defined in step (iv) of claim 1 (DD left tail);
(v) calculating the number of metabolites measured in step (i) selected from 3-indoxylsulfate, isovalerylglycine, p-cresol sulfate, and phenylacetylglutamine with a level in the sample at or above the upper threshold as defined in step (iv) of claim 1 (DD right tail);
wherein a higher number of metabolites calculated in (iv) and (v) is indicative of a higher likelihood that a subject has DD; and
(vi) determining that the subject has ASD or DD based on the number obtained in steps (ii)-(iii) and/or (iv)-(v).
5. The method of claim 4 , wherein the blood sample is a plasma sample.
6. The method of claim 4 , wherein the metabolites are measured by mass spectrometry.
7. The method of claim 4 , wherein the subject is no greater that about 54months of age.
8. The method of claim 4 , wherein the subject is no greater than about 36months of age.