Table 3 Overview of studies included in the systematic review

Level II (Double blinded randomised controlled trial)

Bertoglio et al.

2010 [64]

(USA)

30 cases

Cases 3-8 y, 93%M

DSM-IV-TR and ADOS plus non-verbal IQ ≥ 49 measured by Wechsler Preschool and Primary

Scale of Intelligence, Mullen Scales of Early

Learning or Wechsler Intelligence Scale for Children.

Plasma GSH and GSH: GSSG linked to Global Clinical Impressions Score and other objective behavioural measures.

Adams et al

2009 [65, 67]

(USA)

Baseline

77 cases

RCT

41 cases (26

intervention, 15

placebo)

Baseline

Cases 6.3 (3-8)y, 89.6% M

(95% autistic disorder, 3% PDD-

NOS, 3% Asperger's Syndrome.

RCT

Intervention 6.7 y, 92.3%M (96% autistic disorder, 4% Asperger's)

Placebo 6.5 y, 93.3%M (100%

autistic disorder)

Previous diagnosis of

ASD. No standardised definition.

Erythrocyte glutathione. Behavioural measures.

Open-labelled non-randomised control trial

Rossignol et

al. 2007 [49]

(USA)

18 cases

Cases 3-16 y, 78%M

No seizures. Many

supplemented with folinic acid

and/or methyl-cobalamin.

DSM-IV for autistic disorder, CARS

Plasma GSH measured before and after 40 treatments with hyperbaric oxygen. Behavioural measures.

Level III-2 (Casecontrol)

Golse et al.

1978 [63]

(France)

36 cases, 21

controls

Cases 4-19 y, 58%M

Controls 5-18 y, 43%M

Social isolation, no language, stereotypical behaviour.

Erythrocyte and platelet GPx activity.

Rolf et al.

1993 [68]

(Germany)

18 cases, 14

controls

Cases 9.9 ± 2.8 y (5-14 y)

89%M, medication free.

Controls 11.5 ± 2.0 y (8-14 y)

57%M.

DSM-III for autistic disorder.

Platelet glutamic acid.

Visconti et al.

1994 [69]

(Italy)

37 cases (18 with

EEG

abnormalities),

19 controls

Cases 7 y (3-12 y), 89%M

Controls 7 y (3-13 y), 68%M 1 case and 1 control on thioridazine.

Fasted.

DSM-III-R for autistic disorder.

Serum serine, glutamic acid, glycine and cysteine.

D'Eufemia et

al. 1995 [70]

(Italy)

40 cases,

46 controls

Cases 12 y 4 mo (7-17 y), 68%M,

32 F

Controls 11 y, 2 mo (5-15 y). Medication free for previous

month. Fasted.

DSM-III-R for autistic disorder.

Serum glutamic acid, glycine and cystine.

Yorbik et al.

2002 [71]

(Turkey)

45 cases, 41

controls

Cases 6.4 ± 2.2 y (4-12 y) 87%M

Controls 6.7 ± 2.5 y (4-12 y) 85%M

Medication free for previous

month and fasted.

DSM-IV for autistic disorder.

Plasma and erythrocyte GPx activity.

Söğüt et al.

2003 [72]

(Turkey)

27 cases,

30 controls

Cases 4.7 ± 2.7 y (2-12 y), 59%M

Controls 5.1 ± 2.9 y (2-13 y) 53%M

Medication free and fasted.

DSM-IV for autistic disorder and CARS > 30.

Plasma GPx activity

James et al.

2004 [46]

(USA)

20 cases (19

regressive

autism), 33

controls for the

cross sectional

study then 8

cases for the

intervention.

Cases 6.4 ± 1.5 y, 70%M, 16 supplemented with 400 μg folic

acid and 3 μg vitamin B12.

Controls 7.4 ± 1.3 y, gender not

stated. Supplemented with over

the counter multivitamins.

Both groups medication free and fasted.

DSM-IV for autistic disorder plus diagnostic interview.

Plasma homocysteine, cystathionine, cysteine, tGSH & GSSG measured in all participants. The same parameters were measured before and after 3 mo. folinic acid (800 μg) & betaine (1000 mg) and additional month on same regimen plus vitamin B₁₂ (75 μg\kg) for the intervention study.

Adams et al.

2004 [73]

(USA)

24 cases,

11 controls

Cases 4.9 ± 1.4 y, 92%M

Controls 6-9 y

Diagnosis of an autism spectrum disorder by a psychiatrist or developmental paediatrician.

Plasma vitamin B₆.

James et al.

2006 [47]

(USA)

80 cases

73 controls

Cases 7.3 ± 3.2 y (3-14 y), 89% M

Controls 10.8 ± 4.1 y, gender not stated. Medication and supplement free. Fasted.

DSM-IV, ADOS or CARS for autistic disorder.

Plasma homocysteine, cystathionine, cysteine, cysteinylglycine, tGSH, fGSH, GSSG.

Rose et al.

2008 [50]

(USA)

242 cases, 75

controls

Cases aged 6.9 ± 2.9 y (3-14 y)

Controls aged 10.8 ± 4.1. Gender

not stated. Fasted.

DSM-IV and

ADOS or CARS.

tGSH, fGSH, GSSG. Cases stratified by ALAD polymorphism.

Pasca et al.

2006 [74]

(Romania)

12 cases, 9

controls

Cases 8.3 ± 2.8 y, 75% M

Controls aged 8.3 ± 1.8 y 66% M

Medication and supplement free.

DSM-IV for autistic disorder.

Plasma homocysteine and GPx activity.

Shinohe et al.

2006 [75]

(Japan)

18 cases, 19

controls

Cases 21.2 ± 2.1 y, (18-26 y)

100% M

Controls 22.2 ± 2.2 y, (18-26 y) 100%M

Medication free.

DSM-IV, ADI-R for autistic disorder.

Serum glutamate, glycine and serine. Objective behavioural scores.

Adams et al.

2006 [76]

(USA)

11 cases, 11

controls

Cases 7.2 ± 1.4 y, 73%M

Controls 7.8 ± 1.2 y, 91%M

Both groups were not

supplemented with vitamin B₆ for

the last two months.

Diagnosis of an autism spectrum disorder by a psychiatrist or developmental paediatrician.

Plasma vitamin B₆.

Adams et al.

2007 [59]

(Australia)

17 cases, 16

controls

Cases 2-16 years.

Controls age not stated

DSM-IV for autistic disorder.

Plasma homocysteine.

Suh et al.

2008 [77]

(USA)

31 cases, 11

controls

Cases 4.17 ± 1.3 y, 84%M

Controls 6.9 ± 1.6 y, 82%M

Medication and supplementation

free. Not stated whether fasting.

DSM-IV, ADI-R for

autism spectrum

disorders.

Plasma homocysteine, cystathione, cysteine, tGSH, cysteinyl-glycine.

Jory &

McGinnis

2008 [78]

(Canada)

20 cases, 15

controls

Cases 3.9 ± 1.7 y, 80% M

Controls 3.87 ± 1.1 y 40% M

Medication and supplement free. Fasted.

DSM-IV for autistic disorder.

Erythrocyte selenium levels.

Vojdani et al.

2008 [79]

(USA)

1027 cases, 113

controls

Cases 2-15 y, 75%M

Controls aged 5-15, gender not

stated

DSM-IV and/or ICD-10 For autistic disorder.

Correlation between glutathione and natural killer cell (NK) activity. NK activity and treatment with glutathione.

James et al.

2009 [80]

(USA)

10 case

lymphoblastoid

cell lines

10 control

lymphoblastoid

cell lines

Cases 7.8 ± 3.1 y 100%M

Controls 27.7 ± 9.1 y 100%M.

DSM-IV for autistic disorder

Intracellular glutathione redox status, effect of thimerosal induced and nitrosative oxidative stress on GSH:GSSG.

James et al.

2009 [48]

(USA)

48 cases, 42

controls

Cases 4.8 ± 0.8 y, 82%M

Controls 4.5 ± 0.9 y, gender not stated. Supplement free and fasted.

DSM-IV for autistic disorder and CARS > 30

Plasma homocysteine, cysteine, cysteinylglycine, tGSH, fGSH, GSSG before and after 3 mo. intervention with folinic acid (400 μg) and vitamin B₁₂ (75 μg/kg).

Al-Gadani et

al. 2009 [81]

(Saudi Arabia)

30 cases, 30

controls

Cases 3-15 y, 73%M

Controls 3-15 y, 67%M Medication and supplementation free. Fasted.

DSM-IV for autistic disorder.

Plasma GSH and GSH-Px activity.

Pasca et al.

2009 [60]

(Romania)

15 cases, 13

controls.

Cases 5.1 ± 0.45 y, 87%M

Age and gender matched. Supplement free. Fasted.

DSM-IV-R for autistic disorder, PDD-NOS or Asperger's Syndrome.

Plasma homocysteine, cysteine, cystathionine, serine, glycine. Whole blood tGSH.

Pastural et al.

2009 [82]

(Canada)

15 cases, 12

controls

Cases 7.9 y (2-13 y) 100%M

Controls 8.7 y (4-17 y) 75%M

DSM-IV for autistic disorder.

Plasma homocysteine, cysteine and tGSH. Glutamate toxicity in neuronal, astrocyte and hepatocyte cell cultures.

Mostafa et al.

2010 [83]

(Egypt)

44 cases, 44

controls

Cases median 8 y (3.5-12 y),

68%M

Controls median 8 y (4-12 y),

DSM-IV for autistic disorder.

Plasma GPx activity

Vergani et al.

2011 [84]

(Italy)

28 cases, 32

controls

Cases 2-6 y, 75%M

Controls 62.5%M

DSM-IV for autistic disorder.

Erythrocyte GPx activity.

Al-Yafee et

al. 2011 [85]

(Saudi Arabia)

20 cases

20 controls

Cases (3-16 y), 100%M, 100% IQ < 80. Controls 3-16 y, 100% M.

ADI-R and ADOS and Developmental, dimensional diagnostic interview.

Total glutathione, oxidised glutathione, tGSH:GSSG, glutathione reductase and gluthathione-s-transferase activity.

Tirouvanziam et al. 2011 [86]

(USA)

27 cases

20 controls

Cases 7.0 ± 2.3 y, 77.8%M

Controls 7.3 ± 2.5 y, 45%M

ADI-R and ADOS for autistic disorder. ADI-R score 7-10 plus ADOS criteria for autism for PDD-NOS.

Platelet poor plasma glutamine, serine and glycine.

Adams et al.

2011 [87]

(USA)

55 cases

44 controls

Cases 10.0 ± 3.1 y, 89%M

Controls 11.0 ± 3.1 y, 89%M

Prior diagnosis by a child psychiatrist or developmental paediatrician.

Plasma glutamate, serine, GSH and GSSG. Selenium (whole blood and erythrocyte).

Case Control Level III-3

Aldred et al.

2003 [88]

(UK)

23 cases (12

autistic disorder,

11 Asperger's syndrome), 32

parents, 23

siblings.

Cases

Autism 16.4 ± 9.04 y, 92%M

Aspergers 15.7 ± 8.63 y, 91%M Parents 44.1 ± 6.9 y, 44%M

Siblings 16.5 ± 6.4 y, 39%M

DSM-IV for autistic disorder or Asperger's Syndrome.

Plasma serine and glycine.

Arnold et al.

2003 [89]

36 cases (mixed

autistic disorder

and PDD-NOS)

(10 gluten/casein

free diet).

24 controls.

Cases

Aged < 5 years, gender

unknown.

Controls

Age and gender matched with

cases on a regular diet.

DSM-IV supported by CARS or the pervasive Developmental Disorders Screening Test.

Plasma glutamine.

Geier & Geier

2009 [90]

(USA)

28 cases (20

autistic disorder,

8 other ASD) 64

controls for

cysteine and

120 controls for glutathione

measurements.

Cases 5.8 ± 2.7 y, 82% M

50% mild, 50% severe autism.

Controls 2-16 y. Gender

unknown.

CARS > 30.

Mild autism CARS 30-38.5

Severe autism CARS > 38.5

Cysteine, reduced and oxidised glutathione.

Geier & Geier

2009 [91]

(USA)

38 cases (28

10 other ASD)

Controls as

above.

Cases 6.0 ± 2.6 y, 89.5% M

Controls as above.

CARS > 30

As above.

Sankar 1979

[92] (USA)

19 cases

Age within the range 5-16 y,

100%M Medication and

supplement free for 3 weeks

prior to fasted blood draw.

Onset from infancy with severe emotion-al isolation; failure to relate to objects & persons; failure to develop speech & communication. If speech present, it is a non-communicative type. Stereotypy of motor behaviour.

Serum vitamin B₆.

Khaludeenin

& Philpott

1980 [93]

(USA)

9 cases

Cases mean 9 y, 78%M

Not provided

Plasma cystine, cystathione, glutamic acid and vitamin B₆.

Level IV (Case series)

Geier & Geier

2006 [66]

(USA)

16 cases

Cases 5.9 ± 2.1 y

Not provided, relied on previous diagnosis.

Plasma cysteine and reduced glutathione, serum cystathionine and cysteine.

Level IV (Case report)

Moretti et al.

2005 [54]

(USA)

1 case

Case aged 6 y, F

ADOS, ADI-R for autistic disorder.

Cerebral spinal fluid homocysteine.

Genetic studies

Bowers et al.

2011 [94]

(USA)

318 families

(1,149 individuals

including 457

children) plus

3,327 participants

from independent

AGRE families

for replication.

Cases 77.6% M, 321 sibships, Caucasian 91.68%, American

black 0.22%, unknown 8.1%.

ADI-R and ADOS

for autism spectrum disorders.

308 SNPs of 42

candidate genes

related to

glutathione.

Ming et a l.

2010 [95]

(USA)

103 cases, (101

autistic disorder,

2 PDD-NOS)

including 68 case

trios.

Cases 86%M

ADI-R and ADOS-G

for autistic disorder.

GPx-1

polymorphisms.

Rose et al.

2008 [50]

(USA)

451 cases, 251

controls

Cases aged 6.9 ± 2.9 y (3-14 y)

Controls aged 10.8 ± 4.1.

Gender not stated.

DSM-IV and

ADOS or CARS.

tGSH, fGSH, GSSG stratified by ALAD polymorphism.

Buyske et al.

2006 [96]

USA)

54 case parent

trios

172 controls

45 cases diagnosed as autistic disorder using both instruments,

9 diagnosed as autistic disorder using one instrument and PDD-

NOS using the other.

ADI-R and ADOS-G

for autistic disorder.

GST-M1

polymorphisms

James et al.

2006 [47]

(USA)

360 cases

205 controls

(comprising 73

children and 132

adult females).

Cases 7.3 ± 3.2 y (3-14 y), 89%

M

Controls 10.8 ± 4.1 y, gender not stated (n = 73) plus adult females

of child bearing age (n = 132).

DSM-IV, ADOS or

CARS for autistic

disorder.

GST-M1 and T1 polymorphisms.

Serajee et al.

2004 [97]

(USA)

196 case parent

trios (581 individuals).

Not stated.

DSM-IV for autism spectrum disorder.

GST-P1

polymorphisms.