Translation, cross-cultural adaptation, validity, reliability and stability of the Dutch Injury - Psychological Readiness to Return to Sport (I-PRRS-NL) scale

Figures & data

Table 1. Demographic characteristics of participants and non-responders.

Characteristics	I-PRRS-NL sample (n = 150)	Non-responders (n = 91)	p-value
Age (years)	29.2 (10.8)	26.8 (9.2)	0.06
Time after reconstruction (months)	9.6 (4.0)	9.9 (3.9)	0.94
Gender			0.56
Male (%)	84 (56%)	54 (59%)
Female (%)	66 (44%)	37 (40%)
Height (cm)	178 (9.4)	178 (12)	0.65
Body weight (kg)	79 (17)	81 (16)	0.38
BMI (kg/m2)	24.8 (4.3)	25 (7.3)	0.25
Graft type			0.57
Semitendinosis/Gracilis (%)	143 (95%)	86 (95%)
Bone-tendon-bone (%)	7 (5%)	5 (5%)
Tegner activity level score	5.5 (2.2)	-

Age, time after reconstruction, height, body weight, BMI and Tegner activity level are given as mean (standard deviation). Other values are given as number of patients (%).

Table 2. Descriptive statistics of the various measurements and Spearman correlation between the I-PRRS-NL and other questionnaires in the validity study (N = 150).

	Mean	SD	Min.	Max.	r	p-value
I-PRRS	43.2	13.1	0	60
ACL-RSI	56.5	22.2	8.3	100	0.79	< 0.001
KOOS subscale “Pain”	84.1	15.6	22.2	100	0.38	< 0.001
KOOS subscale “Other symptoms”	75.9	16.5	32.1	100	0.36	< 0.001
KOOS subscale “Function in daily living”	91.1	14.8	0	100	0.30	< 0.001
KOOS subscale “Function in Sport and Recreation”	65.9	23.3	0	100	0.53	< 0.001
KOOS subscale “Knee-related Quality of life”	49.7	13.0	18.8	81.3	0.45	< 0.001
IKDC 2000	76.9	16	6.9	100	0.56	< 0.001
TSK	36.6	6.5	17	56	−0.40	< 0.001
MHLC-C	19.4	6.2	6	36	−0.08	0.369

I-PRRS, Injury-Psychological Readiness to Return to Sport scale; ACL-RSI, Anterior Cruciate Ligament – Return to Sports after Injury scale; IKDC, International Knee Documentation Committee Score; MHLC-C, Multidimensional Health Locus of Control, C form; TSK, Tampa Scale of Kinesiophobia; KOOS, Knee injury and Osteoarthritis Outcome Score

Table 3. Predefined hypotheses (all hypotheses were confirmed).

	Expected correlation	True correlation
- High correlation between I-PRRS-NL and ACL-RSI(NL)	> 0.6	0.79
- Moderate correlation between I-PRRS-NL and KOOS(NL) subscale “pain”	0.3–0.6	0.38
- Moderate correlation between I-PRRS-NL and KOOS(NL) subscale “or symptoms”	0.3–0.6	0.36
- Moderate correlation between I-PRRS-NL and KOOS(NL) subscale “Function in daily living”	0.3–0.6	0.30
- Moderate correlation between I-PRRS-NL and KOOS(NL) subscale “Function in Sport and Recreation”	0.3–0.6	0.53
- Moderate correlation between I-PRRS-NL and KOOS(NL) subscale “Knee related Quality of life”	0.3–0.6	0.45
- KOOS(NL) subscales “Function in Sport and Recreation” and “Knee-related Quality of life” have a stronger correlation with ACL RSI than the other three subscales
- Moderate correlation between I-PRRS-NL and IKDC 2000(NL)	0.3–0.6	0.56
- Moderate correlation between I-PRRS-NL and TSK(NL)	0.3–0.6	0.40
- Low correlation between I-PRRS-NL and MHLC-C(NL)	< 0.3	0.08

Table 4. Test-retest reliability measures of the I-PRRS-NL scale (N = 104).

I-PRRS-NL First administration (SD) I-PRRS-NL Second administration (SD) Mean difference (95% CI; SD) LOA ICC (95% CI) SEM SDC – individual SDC – group

43.9 (13.0) 43.9 (11.7) 0.08 (−1.04–0.88; 5.9) -11.48–11.64 0.89 (0.84–0.92) 4.2 11.6 1.1

Abbreviations: SD = standard deviation; CI = confidence interval; LOA = limits of agreement; ICC = intraclass correlation coefficient; SEM = standard error of measurement; SDC = smallest detectable change

Figure 1. Bland and Altman graph of the test and retest.

Mean difference 0.08; 95% CI −1.04–0.88; containing zero

Table 5. Frequency distribution of test-retest differences (within-individuals) for items 1–6 of the I-PRRS.

Differences between test 2 and test 1	Frequency (%)
	Item 1	Item 2	Item 3	Item 4	Item 5	Item 6
−81/-90	1 (1.0)	0	0	0	0	0
−71/-80	0	0	0	0	0
−61/-70	0	1 (1.0)	0	0	0	0
−51/-60	1 (1.0)	0	0	0	1 (1.0)	1 (1.0)
−41/-50	0	3 (2.9)	1 (1.0)	1 (1.0)	0	3 (2.9)
−31/-40	0	2 (1.9)	1 (1.0)	2 (1.9)	1 (1.0)	1 (1.0)
−21/-30	2 (1.9)	1 (1.0)	2 (1.9)	3 (2.9)	3 (2.9)	2 (1.9)
−11/-20	9 (8.7)	13 (12.5)	7 (6.7)	10 (9.7)	9 (8.7)	4 (3.8)
−1/-10	28 (27.0)	22 (21.2)	11 (10.6)	13 (12.6)	24 (23.4)	25 (24.9)
0	39 (37.5)	36 (34.6)	44 (42.3)	36 (34.6)	33 (32)	42 (40.8)
1/10	15 (14.5)	18 (17.3)	23 (22.1)	21 (20.2)	17 (16.5)	20 (19.4)
11/20	5 (4.8)	4 (3.8)	5 (4.8)	7 (6.8)	8 (7.7)	3 (2.9)
21/30	3 (2.9)	1 (1.0)	3 (2.9)	3 (2.9)	3 (2.9)	0
31/40	0	1 (1.0)	1 (1.0)	3 (2.9)	2 (1.9)	0
41/50	1 (1.0)	2 (1.9)	3 (2.9)	3 (2.9)	1 (1.0)	1 (1.0)
51/60	0	0	2 (1.9)	1 (1.0)	1 (1.0)	0
61/70	0	0	1 (.0)	0	0	0
71/80	0	0	0	0	0	1 (1.0)
81/90	0	0	0	0	0	0
91/100	0	0	0	1 (1.0)	0	0

Difference = test 2 – test 1 (within-individuals). Frequency distribution is given as number of participants (%)

Table 6. 2.5th and 97.5th percentiles, proportion of participants with test-retest differences lower than or equal to ± 10 (PA ± 10), and proportion of agreement (PA) for the six items of the I-PRRS.

Item	Percentiles
	2.5%	97.5%	PA ± 10 (%)	PA (%)
1	−41	30	82 (79.0)	39 (37.5)
2	−50	44	76 (73.1)	36 (34.6)
3	−32	60	78 (75.0)	44 (42.3
4	−37	54	70 (67.4)	36 (34.6)
5	−34	44	74 (71.9)	33 (32)
6	−50	32	87 (85.1)	42 (40.8)