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Table 2 Primary outcome analysis methods

From: Analysis and reporting of stepped wedge randomised controlled trials: synthesis and critical appraisal of published studies, 2010 to 2014

Author, year

Model fitted

Effect estimated

Vertical and/or horizontal analysis

Method to account for clustering

Repeated measures on individuals? Method used

Adjustment for confounding?

Adjustment for secular trends

Risk of lag

Accounting for lags

Risk of fidelity loss

Bacchieri, 2010 [29]

Poisson regression

Rate ratio

Both

Robust standard errors

Time-to-event

No

Fixed effect (no interaction)

None

None

Minor

Bashour, 2013 [22]

Linear regression

Mean difference

Both

Random effects

No

Yes

Fixed effect

None

None

Major

(no interaction)

Durovni, 2013 [12]

Cox regression

Rate ratio

Within-step only, plus frailty

Random effects

Time-to-event

Yes

Conditional

Major

None

Minor

Fuller, 2012 [23]

Logistic regression

Odds ratio

Both

Random effects

Yes, not explicitly accounted for

Yes

Fixed effects

Major

None (per-protocol analysis using observed lags)

Major

(no interaction)

Gruber 2013 [21]

Linear regression, Log-Poisson regression

Risk difference, risk ratio

Both

Robust standard errors, GEE

Yes, not explicitly accounted for

Yes, in secondary analyses

Fixed effect

Major

None

Low

(no interaction)

Horner, 2012 [27]

Logistic regression

Odds ratio

Both

Random effects

Yes, not explicitly accounted for

Yes

Fixed effect

Minor

None

Minor

(no interaction)

Mhurchu, 2013 [24]

Logistic regression

Odds ratio

Both

Random effects

Yes, pupil-level summaries and random effect

Yes

Fixed effect

None

None

Minor

(no interaction)

Roy, 2013 [25]

Logistic regression

Odds ratio

Both

Random effects

No

Yes

None

None

None

Minor

Schultz, 2014 [28]

Logistic regression

Odds ratio

Both

None: GEE not possible, and RE did not converge

No

No

Fixed effect

Minor

None

None

(no interaction)

Stern, 2014 [26]

Linear regression

Mean difference

Both

Random effects

Yes, multiple level random effects

Yes

Fixed effect with interaction

Major

None

Minor