Table 3

ITS methodological considerations of included studies

Characteristicsn%
ITS design reported in the title and/or abstract120100
Background/rationale reported11898.3
Study objectives reported120100
Description of QI intervention11696.6
Start (and end) of QI intervention reported120100
Multiple QI interventions2520.8
  • 2 interventions

2288
  • 3 interventions

14
  • 4 interventions

28
Adjusted multiple interventions in the analyses1976
Study setting reported120100
Multisite5344.2
Study period reported120100
Study population reported120100
Cohort definition reported120100
Inclusion criteria reported120100
Data sources reported11999.2
Data completeness and validity reported1411.6
Time point intervals, monthly8571.4
Data collected regularly (regular interval)11999.2
Time points clearly reported11999.2
Rationale for the number and spacing of data points described5142.5
Outcome measure(s) reported120100
Format of outcome(s) reported120100
Unit of analysis
  • Aggregated

5142.5
  • Individual

119.2
  • Not reported

5848.3
ITS models
  • Segmented regression

7562.5
  • ARIMA

1915.8
  • Other models (eg, GEE, linear regression, mixed effect model, spline regression, poison regression, Prais-Winsten regression, logistic regression)

1714.2
  • Not reported

1411.6
Autocorrelation
  • Checked/adjusted as appropriate

6655
Test(s) used to check for autocorrelation
  • Durbin-Watson test statistic

2436.4
  • Other tests (eg, ACF and PACF, Ljung-Box χ2 test, residual plots and Breusch-Godfrey test, Breusch-Godfrey test, Cumby-Huizinga test)

1015.2
  • Not reported

3350
Seasonality
  • Checked/adjusted

2520.8
Non-stationarity
  • Checked/adjusted

108.3
Test(s) used to check
  • Augmented Dickey-Fuller test

770
  • Not reported

220
Control group used2218.3
Type of control, location-based control1359.1
Analyses of controlled ITS
  • Combined

522.7
  • Separated

1254.5
  • Difference

29.1
  • Not reported

313.6
Specify ITS impact model (or provided basic ITS model structure)5949.2
Use of lag period3428.4
Sensitivity analyses1512.5
Reported statistical software used9780.8
  • ACF, autocorrelation function; ARIMA, autoregressive integrated moving average; GEE, generalised estimating equation; ITS, interrupted time series; PACF, partial autocorrelation function; QI, quality improvement.;