Table 1

Overview of the most prominent results
Variable PRO-studies CM-studies Total-studies
n % * n % * n % *
US 26 30.6 4 28.6 30 30.3
UK 24 28.2 2 14.3 26 26.3
Netherlands 11 12.9 4 28.6 15 15.2
Canada 10 11.8 1 7.1 11 11.1
Other 32 37.6 5 35.7 37 37.4
Cross-sectional 76 89.4 14 100.0 90 90.9
Longitudinal 13 15.3 2 14.3 15 15.2
RA 43 50.6 5 35.7 48 48.5
OA 31 36.5 3 21.4 34 34.3
Other 31 36.5 7 50.0 38 38.4
Overall physical functioning 33 38.8 2 14.3 35 35.4
Quality of life 26 30.6 2 14.3 28 28.3
Specific functioning 10 11.8 0 0.0 10 10.1
Pain 7 8.2 0 0.0 7 7.1
Psychological constructs 3 3.5 0 0.0 3 3.0
Work disability 5 5.9 0 0.0 5 5.0
Disease activity 0 0.0 3 21.4 3 3.0
Disease damage or radiographic severity 0 0.0 3 21.4 3 3.0
Other 11 12.9 4 28.6 15 15.2
Development/evaluation new measures 25 29.4 2 14.3 27 31.4
Evaluation existing measures 31 36.5 6 42.9 37 37.4
Development/evaluation alternate/short form 11 12.9 2 14.3 13 13.1
Development item bank or CAT 4 4.7 0 0.0 4 4.0
Cross-cultural validation 7 8.2 2 14.3 9 9.1
Other 11 12.9 3 21.4 14 14.1
Bigsteps/Winsteps 28 32.9 3 21.4 31 31.3
RUMM 29 34.1 6 42.9 35 35.4
Other/not specified 29 34.1 5 35.7 34 34.3
Rasch 72 84.7 12 85.7 84 84.8
2-PLM 13 15.3 1 7.1 14 14.1
Mokken 3 3.5 1 7.1 4 4.0
Unidimensionality 65 76.5 10 71.4 75 75.8
Local independence 16 18.8 1 7.1 17 17.2
Appropriateness model (fit analyses) 77 90.6 13 92.9 90 90.9
DIF 50 58.8 6 42.9 56 56.6
Person/item separation/reliability 52 61.2 10 71.4 62 62.6
Hierarchical ordering/distribution of items/persons 57 67.1 9 64.3 66 66.7
Rating scale analysis 30 35.3 7 50.0 37 37.4
Measurement precision of the scale 10 11.8 1 7.1 11 11.1

PRO: patient-reported outcome (N=85), CM: clinical measure (N=14), RA: rheumatoid arthritis, OA: osteoarthritis, CAT: computerized adaptive test, IRT: item response theory, 2-PLM: 2 parameter logistic model, DIF: differential item functioning.

* Note that some studies can be assigned to multiple subcategories, therefore, the sum of the percentages within a category exceeds 100%.

Siemons et al.

Siemons et al. BMC Musculoskeletal Disorders 2012 13:216   doi:10.1186/1471-2474-13-216

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