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Table 5 Methodological quality assessment

From: Associations between psychological factors and health-related quality of life and global quality of life in patients with ALS: a systematic review

Reference Year Internal validity Control of drop out External validity Statistical validity Proportion
Sample size vs determinants
Multi-collinearity Confounding bias Reporting Total (max 8 points)
Bremer [16] 2004 1 1 1 1 0 0 0 1 5.0
Chio [13] 2004 1 0.5 1 1 0 0 1 1 5.5
Clarke [15] 2001 1 1 1 1 0 0 0 1 5.0
Dal-Bello-Haas [47] 2000 1 0 0.5 1 0 0 0 1 3.5
Ganzini [45] 1999 0 1 0.5 1 1 0 1 1 5.5
Gibbons [37] 2013 1 0 1 1 1 1 1 1 7.0
Goldstein [38] 2002 1 0 1 1 0 0 0 0 3.0
Ilse [10] 2015 1 0 1 1 0 0 0 1 4.0
Krampe [27] 2008 0 0 1 1 0 0 1 1 4.0
Lule [28] 2008 1 0 0.5 1 0 0 1 1 4.5
Matuz [36] 2010 1 0 1 1 0 1 1 1 6.0
Matuz [30] 2015 1 1 1 1 0 0 1 1 6.0
McCabe [19] 2009 1 0 0.5 1 1 0 1 1 5.5
Montel [46] 2012 1 0 1 1 0 0 0 1 4.0
Pagnini [29] 2015 1 0.5 0.5 1 1 0 1 1 6.5
Peric [40] 2010 1 0.5 1 1 0 1 1 1 6.5
Pizzimenti [43] 2013 1 1 1 1 1 1 1 1 8.0
Robbins [31] 2001 1 0.5 0.5 1 1 0 1 1 6.0
Simmons [14] 2000 1 0.5 1 1 0 0 0 1 4.5
Tramtoni [42] 2012 1 0 0.5 1 0 0 1 1 4.5
Vignola [41] 2008 1 0.5 1 1 0 0 1 1 5.5
Winter [44] 2010 1 0.5 0.5 1 0 0 1 1 5.0
  1. Note. 1 = internal validity: use of validated and reliable measures, 2 = control of patient drop-out: including nonresponse analysis and describing executive patients, 3 = external validity: specifying in/exclusion criteria and demographic and disease characteristics (diagnosis, age, gender, site of ALS onset, time since diagnosis, severity), 4 = statistical validity: testing for statistical significance, 5 = adequate sample size in relation to the number of determinants (univariate ratio 20:1 and multivariate ratio 10:1), 6 = control for multicollinearity, 7 = control for potential confounding variables, 8 = clear description of main finding [17]