3.5 Association between PEs on the outcomes (pain, functional levels and health related quality of life)
Table 3 shows the association between the PEs and the outcome measures (pain, functional status and health related quality of life) reported among the reviewed studies. The results showed that a total of four trials addressed the association between PEs and pain intensity. Two of these trials demonstrated a positive association between PEs and pain intensity, in both the short (7) and long term (26). The other two trials demonstrated no association between PEs and pain intensity within the medium term follow-up (6, 27). A total of 6 trials addressed the outcome of levels of function. Three of the 6 trials demonstrated a positive significant association between PEs and levels of function, two trials (5, 6) registered at medium term (> 6 weeks - ≤ 6 months) while the other one (26) at long term (> 6 months). Three other trials demonstrated no significant associations between PEs and function levels (24, 25, 27). None of the included trials addressed the outcome of function levels in the short term (≤ 6 weeks). Neither short (≤ 6 weeks) nor the long term (> 6 months) association was reported between PEs and the HRQOL. Only one study (27) reported the association between PEs and HRQOL over the medium follow-up term (> 6 weeks - ≤ 6 months), however the association was not significant.
Discussion
This study investigated the evidence behind the association between PEs and specific treatment outcomes such as pain intensity, functional level and HRQOL among people with CLBP. The findings supported evidence on the association between PEs and the pain and functional levels. Positive PEs prior to the treatment were shown to be associated with the pain intensity in both shorter and longer terms among CLBP individuals. Evidence suggests that PEs have an influence on the pain outcome by means of a ‘placebo’ effect (28, 29). In addition, several psychological factors such as individual’s beliefs about their pain; fear avoidance beliefs; patient’s behaviours; emotions such as anxiety, depression etc., as well as the regulation of these emotions; lack of support; coping strategies; faith and religious beliefs; and patient’s recovery expectations have been discussed in the pain literature as underlying factors that might influence the pain outcomes (30, 31). However, the current findings need to be interpreted with caution in acute and nonspecific low back pain, as the effects might be different because PEs change over time (32-34). Currently, studies that have examined the association between PEs and treatment outcomes on acute low back pain are lacking and hence, the influence of PEs is unknown among people with acute low back pain. Also, the studies have only measured the PEs at one point in time, it would be interesting to know if or how they change throughout a course of treatment
Past studies reported that the positive PEs on an intervention have positively influenced the functional outcomes (5, 35). However the current review finding suggests that there is equivocal evidence between PEs and levels of function. While three studies showed a positive association between PEs and the levels of function at both medium and long term (5, 6, 26), three other trials demonstrated no significant associations between PEs and function levels (24, 25, 27). The therapist-patient encounter, information provided to the patients during the encounter, different timings of measuring PEs and use of various methods to measure PEs might have contributed to this equivocal evidence (10). While patients with higher expectations for benefiting from joint replacement surgery had greater gains in HRQOL (36), the findings of the current review clearly demonstrated no evidence behind PEs and HRQOL among people with CLBP. Neither short (≤ 6 weeks) nor the long term (> 6 months) association was reported between PEs and the HRQOL. Only one study (27) reported the association between PEs and HRQOL over the medium follow-up term (> 6 weeks - ≤ 6 months), however the association was not significant. Further studies are warranted to investigate the influence of PEs on HRQOL among people with CLBP in order to revaluate and reflect on this evidence again in practice.
The review findings have some implications for policy makers and clinical managers in the health care sector. The Care Quality Commission (CQC) ensures the quality of healthcare provided by the majority of hospital-based care for the National Health Service (NHS) in the UK (37). PEs of a given care is one of the major determinants for satisfaction in the quality of health care provided to people (38). While the CQC’s quality surveillance tool effectively monitors the quality of care through monitoring care profile indicators such as mortality rates, timeliness of intervention, waiting times etc. (37), there is no explicit mention about collecting or documenting PEs on the care provided. Similarly, NHS collect feedback on the quality of care provided to the patients, however, it does not collect information on the PEs of care (39, 40). Perhaps, a lack of sufficient understanding and evidence behind the influence PEs could have on the treatment outcomes might be one of the reasons that PEs are not fully represented in both CQC and NHS audit policies. In the above given context, the current review might contribute to CQC and NHS policies in future as it provide preliminary evidence on the impact of PEs on the treatment outcomes in CLBP care. As patients are ultimately the receivers of health care provision, understanding and managing their expectations of care in clinical practice is pivotal (41).
However, PE is often handled as a challenging concept in clinical practice. Firstly, a huge overlap and differences in the terminologies used to define PE often cause challenges to practitioners and researchers to measure and understand the concept of PEs in clinical practice. Secondly, although many practitioners might sometimes informally ask the patients about their expectations about treatment, PEs are not explicitly measured and documented in health care practice. Thirdly, even if practitioners do inquire about PEs, it might be generally asked only prior to the initial treatment, however, PEs might not be followed up in consecutive treatment sessions in practice. The timing of measuring PEs is relevant in practice especially when PEs were reported to change over a course of three months among people with CLBP (32-34). Also, one could argue that monitoring PEs may help clinicians in the process of decision making (29). However, there is a lack of a standardized and valid tool in clinical practice to measure PEs (8, 9, 14), hence PEs might be measured differently by different practitioners in day to day practice. Another challenge in practice includes the practitioners measuring PEs at different point of time, as the current review findings supported that the timing of measuring PEs varied between immediately after treatment to the 1- and 5-year follow-up among the studies. In the context of the above mentioned challenges in clinical practice, the findings of the review emphasize to clinicians and researchers the importance and relevance of considering PEs in the development and delivery of health care services. Equally, the review findings identifies a need for a valid tool to measure PEs in practice and calls the international research community towards the development of a clinical tool to measure PEs.
Conclusion
In summary, PEs have a positive association on both the short and long term pain outcomes among individuals with CLBP. The influence of PEs on the functional outcomes among people with CLBP are inconclusive as the evidence on the association between PEs and functional outcomes is equivocal. Limited available studies showed no evidence of an association between PEs and HRQOL among CLBP patients. Further studies investigating the influence of PEs with valid tools to measure PE across standardized time periods and during a treatment programme are warranted in people with CLBP.