Page 104 - THE PERCEPT STUDY Illness Perceptions in Physiotherapy Edwin de Raaij

Chapter 5
three clinical outcomes. This indicates that the Brief IPQ-DLV (9-items) could not be replaced by the 4DSQ (50-items), and that neither makes a clinical contribution of added predictive value for poor recovery.
Limitations and strengths
First, despite the large number of participating primary care physiotherapy centers, selection bias may have occurred. Gender differences are reported for increased female risk of chronic pain and more severe pain 3. This might be of influence on the outcome since 68.9% of our population was female. Additionally, we have no information about patients who were invited but did not participate. Further, we used the Brief IPQ-DLV and, although this is frequently used 7, it is debatable whether dimensions of beliefs about MSP can be measured with questionnaires alone 38. Qualitative research might add extra in-depth information, but this was outside the scope of this study. Finally, the general prognostic factors were based on a systematic review among a range of musculoskeletal disorders 2. Though this suited our population well, it is possible that we have overlooked other general relevant factors, such as sleep or central sensitization.
A strength of this study is that it is the first multicenter study done in primary care physiotherapy centers, with 28 primary care physiotherapy centers, geographically spread throughout the Netherlands. Hence, our findings are generalizable to patients in private practice in the Netherlands. Secondly, according to Hayden et al.’s criteria 19, our design is the first Phase 3 outcome prediction study focusing on the added predictive value of IPs. A systematic review of association and prognosis of IPs in MSP reported no other similar studies 29. Thirdly, although there were missing data, the highest rate was 11%, making our dataset robust enough without the need for imputation. As this is the first paper to report on IPs and poor recovery in primary care physiotherapy, we built exploratory models based on univariate p-values (Table 4). To overcome the issue of excluding possible relevant IPs we set the p-value threshold to 0.10.
Practical implications/ future directions
Overall, the additional contribution of the two IP dimensions, Treatment Control and Timeline, to predictions of poor recovery after three months of usual physiotherapy care were small, the increase in the AUC being only 2-3 percent. Based on these results, assessing baseline IPs, over and above the known generic prognostic factors, does not result in a substantial improvement in the prediction of poor recovery. In addition, the baseline outcome score of the Brief IPQ-DLV does not indicate the use of the questionnaire as a baseline predictor of poor recovery.
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