Page 84 - THE PERCEPT STUDY Illness Perceptions in Physiotherapy Edwin de Raaij

Chapter 4
Pain intensity
The multiple linear regression (Table 4) showed 22.9% of explained variance. The IP dimensions Consequences (beta = 0.098), Identity (beta = 0.273) and Coherence (beta = 0.084) were the statistically-significant contributors to pain intensity.
In the first step (where the confounders and prognostic factors were entered into the mod- el), the explained variance was 9.6%. This means that an additional 13.3% of the variance was explained by adding the IPs to the model.
Physical functioning
The multiple linear regression (Table 4) showed 32.2% of explained variance. The IP dimensions Consequences (beta = 0.283), Identity (beta = -0.113), Treatment Control (beta = 0.240)and Concern (beta =-0.108) were the statistically-significant contributors to physical functioning. In the first step (where the confounders and prognostic factors were entered into the model), the explained variance was 5.7%. This means that an additional 26.5% of the variance was explained by adding the IPs to the model.
Discussion
To our knowledge, this is the first multicentre study of IPs in patients with MSP in primary care physiotherapy. Our findings enhance the understanding of IPs as possible associating factors with pain intensity and limitations in physical functioning in MSP.
Illness perceptions and pain duration
Our results show most IPs being significantly different between the pain-duration groups of acute, subacute and persistent pain. However, looking at the absolute mean differences between pain-duration groups, most IPs show no relevant difference apart from the IP Timeline. This invites the hypothesis that, the longer a patient experiences MSP, the higher the score on the IP Timeline will be. None of the other IP dimensions exceeded the smallest detectable change of 2.58. Therefore, the differences according to pain duration in most IPs are not clinically relevant. This might indicate that high scoring (dysfunctional) IPs are equally important for patients with acute, sub-acute and persistent pain. This is supported by qualitative research about perceptions, such as vulnerability, and poor prognoses for back pain7. In this study, patients shared the same beliefs about their pain condition despite having acute or persistent pain. Though caution in the interpretation of the results is required, due to recallbias12 andthecross-sectionaldesign,weseepossibleimplicationsforthemanagement of MSP.
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