Table 3

Methodological choices in the area of ‘data analysis’

TopicsResults from studies in inflammatory arthritis (n=58)Aspects identified by authors of SLRs in other chronic diseases (n=24)
n/N* (%)Detailed informationN† (%)Comments
10. Accounting for skewness of the outcome10/‡52 (19%)Sick leave is reported as positively skewed (zero-inflated) in 10/46 (22%) studies. The authors accounted for skewness by:

  • Dichotomising the outcome: 2/10 (20%)20 63

  • Analysing the outcome as categorical variable: 2/10 (20%)46 50

  • Using non-parametric bootstrapping: 4/10 (40%)22 45 47 65

  • Using zero-inflated models‡: 2/10 (20%)58 59


Presenteeism was reported as zero-inflated in 1/40 (3%) study. The authors accounted for skewness by using zero-inflated models‡; 1/1 (100%)58		Not reported–
11. Accounting for interdependence of outcomes49/52§ (94%)Interdependence was accounted for in 49 studies by—n/N*:

  • Assessing sick leave only among employed patients: 43/46 (93%)18–22 24–27 29 31–39 42–47 50–56 58–60 63 65–69 71 73

  • Assessing presenteeism among employed patients that were not in sick leave: 37/40 (90%)18–22 24–26 31–39 42 43 50–56 58–60 62–64 67–69 71 73

Not reported–
12. Accounting for contextual factors25/58 (43%)Contextual factors were accounted for in 8/22 (36%) RCTs and 17/36 (47%) OBS—n/N*:

  • As covariates/confounders¶


Personal factors: sociodemographics (7/8 RCTs,19 25 36 37 49 67 69 88% and 15/17 OBS,16 20 27 41 44 46 50 56–58 61 65 66 70 72 88%)
Work-related factors: workplace support (1/17 OBS50, 6%), nature of work (4/17 OBS,27 41 58 70 24%)

  • Effect modification¶


Personal factors: sociodemographics (1/8 RCT,52 13% and 2/17 OBS,23 63 12%)
Work-related factors: nature of work (1/17 OBS,63 6%)		12 (50%)Adjustment for contextual/confounder factors in the included studies, if any, is performed only for very few factors
101 105 107 109 110 112–117 120

  • *The denominator may vary according to the topic assessed.

  • †Number of systematic literature reviews in other chronic diseases in which the authors report on the corresponding topic.

  • ‡Tillet et al (2017) accounted for skewness of both sick leave and presenteeism.

  • §Studies addressing work status only were excluded from the denominator as interdependence between work outcome domains does not apply to them.

  • ¶Different contextual factors may have been accounted for in the same study.

  • n/N, number of original studies in which the methodological choice was identified/number of studies in which the topic was possible to assess; OBS, observational longitudinal study; RCT, randomised controlled trial.