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Table 4 Quality assessment for the included studies

From: Effects of inflammation on the kynurenine pathway in schizophrenia — a systematic review

Year

Author

Sample Size

Q1

Q2

Q3

Q4

Q5

Q6

Q7

Q8

Q9

Q10

Q11

Q12

Controls

Patients

A. Immunoglobulins

 2017

Kanchanatawan et al.

40

84 clinically stable Sz outpatients

Yes

CD

NR

Yes

Yes

Yes

NR

Yes

NA

Yes

NR

Yes

 2018a

Kanchanatawan et al.

40

80 Sz outpatients, 40 deficit, and 40 non-deficit patients

Yes

Yes

Yes

Yes

Yes

Yes

No

No

Yes

Yes

NA

Yes

 2018b

Kanchanatawan et al.

40

80 Sz outpatients, 40 deficit, and 40 non-deficit patients

Yes

CD

Yes

Yes

Yes

Yes

NR

CD

NA

Yes

Yes

Yes

 2010

Bechter et al.

4100

Inpatient Sz = 39, inpatient Af = 24

Yes

Yes

No

Yes

Yes

Yes

No

No

Yes

Yes

NA

No

B. Interleukins

 2017

Szymona et al.

45

51 Sz inpatients due to acute relapse at time of admission, after a 4-week treatment and remission

Yes

Yes

NR

Yes

Yes

Yes

NR

Yes

NA

Yes

Yes

Yes

 2009

Barry et al.

36

34 outpatients (Sz or SzA disorder

Yes

Yes

No

Yes

Yes

Yes

No

No

Yes

Yes

NA

Yes

 2009

Kim et al.

174

71 acute admitted medication-naïve psychotic patients or medication-free for at least 4 months assessed on admission and discharge after 6 weeks.

Yes

Yes

NR

Yes

Yes

Yes

NR

CD

NA

Yes

Yes

Yes

 2015

Schwieler et al.

37

23 Sz outpatients

Yes

Yes

No

Yes

Yes

Yes

No

No

Yes

Yes

NA

Yes

 2017

Kegel et al.

Outpatient (MZ)

Outpatient (DZ)

Yes

Yes

No

Yes

Yes

Yes

No

No

Yes

Yes

NA

Yes

12 (2 single twins)

11 (one single twin)

C. C-reactive protein

 2017

Wurfel et al.

92

Inpatient MDD (N = 35), BD (N = 53), SzA (N = 40), acutely ill Sz (n = 21)

Yes

CD

NR

Yes

Yes

Yes

NR

CD

NA

Yes

Yes

Yes

  1. Abbreviations: CD cannot determine, NA not applicable, NR not reported, Af affective disorder, DZ dizygotic twins, MDD major depressive disorder, MZ monozygotic twins, Sz schizophrenia, SzA schizo-affective disorder
  2. Questions: Q1. Was the research question or objective in this paper clearly stated? Q2. Was the study population clearly specified and defined? Q3. Was the participation rate of eligible persons at least 50%? Q4. Were all the subjects selected or recruited from the same or similar populations (including the same time period)? Were inclusion and exclusion criteria for being in the study prespecified and applied uniformly to all participants? Q5. Was a sample size justification, power description, or variance and effect estimates provided? Q6. For the analyses in this paper, were the exposure(s) of interest measured prior to the outcome(s) being measured? Q7. Was the timeframe sufficient so that one could reasonably expect to see an association between exposure and outcome if it existed? Q8. For exposures that can vary in amount or level, did the study examine different levels of the exposure as related to the outcome (e.g., categories of exposure, or exposure measured as continuous variable)? Q9. Were the exposure measures (independent variables) clearly defined, valid, reliable, and implemented consistently across all study participants? Q10. Was the exposure(s) assessed more than once over time? Q11. Were the outcome measures (dependent variables) clearly defined, valid, reliable, and implemented consistently across all study participants? Q12. Were the outcome assessors blinded to the exposure status of participants? Q13. Was loss to follow-up after baseline 20% or less? Q14. Were key potential confounding variables measured and adjusted statistically for their impact on the relationship between exposure(s) and outcome(s)?
  3. Taken from: The National Heart, Lung and Blood Institute. Study Quality Assessment Tools. Available at: https://www.nhlbi.nih.gov/health-topics/study-quality-assessment-tools