PROMs: The patient is the biggest variable

The article by Stanger and colleagues on the use of patient-reported outcome measures (PROMs) in an orthopaedic surgeon’s office [BCMJ 2016;58:82-89] made an unsubstantiated leap from the article’s findings to the applicability of PROMs. Mention was made of PROMs being used both in assessing appropriateness for surgery and in assisting clinicians in their self-assessment. Also, the claim that the use of PROMs could “contribute to a dramatic change in the way surgical care is provided in BC” was not furthered with examples of these dramatic changes, leaving the reader to speculate. As for the article’s findings, since patient-perceived pain is a large component of both the PROMs and the objective scores used (in the Knee Society score up to 50% of the overall functional score), it is not too surprising that there is a correlation between them.

The biggest variable in any study that assesses the outcome of a treatment is often the patient. Gone are the days when patient cohorts can be assumed to be statistically comparable just because their age and sex distributions are similar. Patient factors including depression, pain catastrophizing, comorbidities, race, and socioeconomic status have all been shown to have significant impacts on both treatment outcomes and PROMs scores.[1-3] All these factors are now measurable and so should be taken into account before attempting to compare treatment outcomes in different patient populations. Following skeletal trauma, catastrophic thinking (as measured with use of the Pain Catastrophizing Scale) has been shown to be the sole significant predictor of pain at rest, pain during activity, and disability.[4]

In 2011 the outcome measures in rheumatoid arthritis clinical trials concluded against the use of PROMs as a discriminator for determining the need for total knee arthroplasty.[5] In similar fashion a further outcome study on the Oxford knee score (adopted in the UK by the National Health Service to measure the outcome of total knee replacement for audit and research purposes) concluded that patient variables would need to be acknowledged and the Oxford knee score adjusted to enable a fair comparison of differing study cohorts or orthopaedic units with dissimilar patient catchment populations.[1] PROMs instruments were designed to compare the effectiveness of forms of treatment, not as tools of diagnosis or indicators of success from interventions.[6] Nor are they a means of assessing patient satisfaction. A study of spine surgery patients showed that preoperative depression scores were indicative of patient dissatisfaction at 2 years after surgery, independent of improvements in pain or disability.[7]

While there may be merit to PROMs data collection as a means of individual practice reflection, their usefulness cannot be extrapolated to treatment or practice comparisons without rigorous patient population standardization.
—Roger Purnell, MB, FRCSC
Prince George

References

1.    Clement ND. Patient factors that influence the outcome of total knee replacement: A critical review of the literature. OA Orthopaedics 2013;1:11.
2.    Clement ND, Jenkins PJ, MacDonald D, et al. Socioeconomic status affects the Oxford knee score and short-form 12 score following total knee replacement. Bone Joint J 2013;95-B:52-58.
3.    Weinberg DS, Narayanan AS, Boden KA, et al. Psychiatric illness is common among patients with orthopaedic polytrauma and is linked with poor outcomes. J Bone Joint Surg Am. 2016;98:341-348.
4.    Vranceanu AM, Bachoura A, Weening A, et al. Psychological factors predict disability and pain intensity after skeletal trauma. J Bone Joint Surg Am. 2014:96:e20.
5.    Gossec L, Paternotte S, Bingham CO 3rd, et al. OARSI/OMERACT initiative to define states of severity and indication for joint replacement in hip and knee osteoarthritis. An OMERACT 10 Special Interest Group. J Rheumatol 2011;38:1765-1769.
6.    Hossain FS, Konan S, Patel S, et al. The assessment of outcome after total knee arthroplasty: Are we there yet? Bone Joint J 2015;97-B:3-9.
7.    Adogwa O, Parker SL, Shau DN, et al. Preoperative Zung depression scale predicts patient satisfaction independent of the extent of improvement after revision lumbar surgery. Spine J 2013;13:501-506.