Translation, cross-cultural adaptation, reliability and construct validity of the Dutch Oxford Knee Score – Activity and Participation Questionnaire

Table 5 Reliability of the Dutch OKS-APQ

Study sample	Pooled sample (n = 131)	Preoperative sample (n = 72)	Postoperative sample (n = 59)
Cronbach α	0.95	0.81	0.95
Test–retest sample		Preoperative sample (n = 12)	Postoperative sample (n = 38)
OKS-APQ test median (25^th–75^th percentile)		9.38 (0.00–29.69)	67.19 (27.34–82.03)
OKS-APQ retest median (25^th–75^th percentile)		15.63 (0.78–28.13)	62.50 (21.88–78.13)
ICC (95% CI)		0.63 (0.10–0.88)	0.85 (0.72–0.92)
Variance components
σ²_p		125.62	820.31
σ²_o		0.00	2.08
σ²_residual		72.02	147.49
SEM		8.49	12.23
SDC_ind		23.53	34.00
SDC_group		6.79	5.52

σ²_p: The variance of the patients (i.e. the systematic differences between the ‘true’ scores of the patients; σ²_o: Variance due to systematic differences between observers/timepoints; σ²_residual: Residual variance (i.e. random error variance)
ICC Intraclass correlation coefficient, SEM Standard error of measurement, SDC_ind Smallest detectable change in one individual, SDC_group Smallest detectable change in a group

ISSN: 1471-2474