Page 81 - THE PERCEPT STUDY Illness Perceptions in Physiotherapy Edwin de Raaij

A cross-sectional study
association we detected the most promising IPs (defined as those with p < 0.10) and added these to the model. We checked on multicollinearity between the IPs, and the distribution of residuals. A variable was considered redundant if its VIF value (indication of multicollinearity) was above 5. Our final model will report if IPs significantly add to the explained variance of pain and physical function, after adjusting for age, gender and well-known prognostic factors.
Results
A total of 658 patients were included in this study: their demographic characteristics are reported in Table 1. For the IPs in the univariate association (Table 3) missing value analyses showed that no IPs variable exceeded over 3.8 percent assumed to be inconsequential.
Table 1: Demographic characteristics of participating patients N =658.
Pain duration groups in weeks prior to consultation
<7 (n =226)
7–13 (n =116)
>13 (n =316)
Age years, mean (sd)
44.5
(13.7)
48.8
(13.0)
46.9
(14.6)
Female (%)
134
(63.3)
79
(68.1)
224
(71.0)
Pain duration in weeks mean (sd)
3.2
(1.5)
9.7
(1.8)
181.0
(336.6)
Pain intensity < 24 h 0–10 mean (sd)
5.2
(2.2)
5.0
(2.2)
5.2
(2.4)
Physical functioning 0–10 mean (sd)
6.2
(2.4)
5.9
(2.2)
6.3
(2.2)
≥2 pain sites (%)
25
(11.1)
23
(19.8)
115
(36.4)
Direct access (%)
130
(57.6)
56
(48.7)
118
(37.3)
sd = standard deviation.
Differences in illness perceptions and pain duration
Illness perceptions mean scores and standard deviations are reported in Table 2. The total between-groups difference was statistically significant, apart from the IP dimension Coherence. The mean differences between acute pain and subacute pain were significant for two out of eight IP dimensions, namely Timeline and Concern. The mean differences between acute pain and persistent pain were significant for seven out of eight IP dimensions (not Coherence). For subacute pain and persistent pain, the differences were significant for two out of eight IP dimensions, namely Timeline and Identity. Overall, absolute point differences were small, with the largest between-groups points differences, ranging between 1 and 3, being for the IP dimensions Timeline, Concern and Emotional.
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