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Table 1 Description of tools used to assess risk of bias

From: Assessing risk of bias in human environmental epidemiology studies using three tools: different conclusions from different tools

Program or agency

Tool

Assessment process

Domains assessed

Number of questions

Available answer options

NTP

OHAT

Risk of bias, internal validity

Selection bias

1

Definitely low ROB; probably low ROB; probably high ROB; definitely high ROB

Confounding bias

1

Definitely low ROB; probably low ROB; probably high ROB; definitely high ROB

Attrition/exclusion bias

1

Definitely low ROB; probably low ROB; probably high ROB; definitely high ROB

Detection bias

2

Definitely low ROB; probably low ROB; probably high ROB; definitely high ROB

Selective bias reporting bias

1

Definitely low ROB; probably low ROB; probably high ROB; definitely high ROB

Other bias

1

Definitely low ROB; probably low ROB; probably high ROB; definitely high ROB

EPA

IRIS

Study evaluation

Exposure measurement

1

Good; adequate; deficient; critically deficient

Outcome ascertainment

1

Good; adequate; deficient; critically deficient

Participant selection

1

Good; adequate; deficient; critically deficient

Confounding

1

Good; adequate; deficient; critically deficient

Analysis

1

Good; adequate; deficient; critically deficient

Selective reporting

1

Good; adequate; deficient

Sensitivity

1

Adequate; deficient

Overall study confidence

1

High; medium; low; uninformative

EPA

TSCA

Data quality criteria for epidemiological studies

Study population

3

High; medium; low; unacceptable

Exposure characterization

3

High; medium; low; unacceptable

Outcome assessment

2

High; medium; low; unacceptable*

*Unacceptable not available for one question

Potential confounding/variable control

3

High; medium; low; unacceptable*

*High and unacceptable not available for one question

Analysis

4

High; medium; low; unacceptable*

*High and low not available for two questions

*High and unacceptable not available for two questions

Biomarker selection and measurement

7

High; medium; low; unacceptable

*High and unacceptable not available for one question

*Unacceptable not available for three questions

Overall study confidence

1

Sum of weighted scores/sum of metric weighting factor

UCSF

Navigation Guide

Risk of bias, internal validity

Source population representation

1

Low; probably low; probably high; high

Blinding

1

Low; probably low; probably high; high

Exposure assessment

1

Low; probably low; probably high; high

Outcome assessment

1

Low; probably low; probably high; high

Incomplete outcome data

1

Low; probably low; probably high; high

Selective outcome reporting

1

Low; probably low; probably high; high

Confounding

1

Low; probably low; probably high; high

Conflicts of interest

1

Low; probably low; probably high; high

Other

1

Low; probably low; probably high; high

  1. Abbreviations: NTP National Toxicology Program, OHAT, Office of Health Assessment and Translation, EPA, Environmental Protection Agency, IRIS Integrated Risk Information System, TSCA Toxic Substances Control Act; ROB risk of bias, UCSF, University of California, San Francisco