Patient Reported Outcome Measures

Written by: Dr Amanda Cormack; additional contribution by: Dr Jeremy Steinberg – created: 15 March 2023; last modified: 15 March 2023

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“"The consequences of our actions are always so complicated, so diverse, that predicting the future is a very difficult business indeed."”
—Albus Dumbledore

In musculoskeletal medicine, patient-reported outcome measures (PROMs) are critical for assessing the impact of treatments on patients' health status. PROMs are particularly useful in this field due to the subjective nature of chronic pain, psychosocial aspects, and disability measures. However, the practicalities of implementing PROMs in clinical settings remain challenging. This article aims to provide an overview of PROMs for musculoskeletal medicine doctors and discuss their relevance, practicalities, and issues.

Outcome Measures and the Backdrop for the Current Conundrum

PROMs feedback in the care of individual patients.

The term "outcome measure" refers to quantifiable aspects of a patient's health status used to assess the benefits of a treatment. In recent years, this term has increasingly been used to describe self-administered questionnaires. These questionnaires aim to measure the change in a patient's status over time, focusing on aspects that are important to the patient.

The 'Outcomes Movement'

The 'Outcomes Movement' has led to the creation of numerous PROMs. The goal of PROMs are to discriminate between patients, predict outcomes, and evaluate change over time. However, few have been validated, and even fewer are suitable for use outside of research settings. There is also a lack of consensus on which PROMs to use.

The collection of PROMs can be paper-based or electronic, and may involve static testing (answering every question) or computerized adaptive testing. Electronic data collection, through clinical research and PROM software or patient apps, can facilitate integration into clinical practice and workflow. For example the questions asked can dynamically change depending on how previous questions are answered. Whether these aspects can be integrated into routine clinical practice is open to debate.

Relevance of PROMs in Musculoskeletal Care

PROMs can be useful in musculoskeletal medicine for the following reasons:

Patients: High relevance due to the subjective nature of chronic pain, psychosocial aspects, and disability measures.
Practice: Important for audit, communication to referrers and 3rd party payers, quality control, and proof of efficacy.
Research: Powerful tools when used appropriately, such as in determining the Minimal Clinically Important Change (or Difference).

Despite their importance, numerous challenges hinder the adoption of PROMs in clinical practice. These challenges include cost, concerns about the relevance to patient care, time-consuming processes, bias from practitioners against reporting subjective findings, and resistance to change.

Example PROMs in Musculoskeletal Medicine

These examples represent a small selection of the many PROMs available for use in musculoskeletal medicine. When choosing a PROM, it is essential to consider its relevance to the specific patient population, its psychometric properties, and its ease of administration and interpretation.

Brief Pain Inventory (BPI): The Brief Pain Inventory (BPI) is a self-report measure for assessing pain severity and its impact on daily functioning in musculoskeletal disorders. It comprises two components, pain severity and pain interference, scored on an 11-point numeric rating scale. The BPI is versatile, suitable for various conditions, and aids in guiding treatment decisions and evaluating efficacy.
Oswestry Disability Index (ODI): The ODI is a widely used, condition-specific PROM designed to assess disability in patients with low back pain. It consists of 10 items, each scored on a 6-point scale. The total score is calculated as a percentage, with higher scores indicating greater disability.
WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index): The WOMAC is a widely used, disease-specific PROM designed to assess pain, stiffness, and physical function in patients with hip or knee osteoarthritis. It is a self-administered questionnaire consisting of 24 items divided into three subscales: pain (5 items), stiffness (2 items), and physical function (17 items).
Oxford Knee Score (OKS): The OKS is a joint-specific, self-administered questionnaire developed to evaluate the outcomes of knee replacement surgery. It consists of 12 items, each scored on a 5-point Likert scale. The total score ranges from 0 to 48, with higher scores indicating better knee function.
Harris Hip Score (HHS): The HHS is a clinician-administered outcome measure designed to evaluate hip function, primarily in patients undergoing hip surgery. It assesses pain, function, deformity, and range of motion, with a total score ranging from 0 to 100. Higher scores indicate better hip function.
Neck Disability Index (NDI): The NDI is a condition-specific PROM developed to evaluate self-rated disability in patients with neck pain. It consists of 10 items, with each item scored on a 6-point scale. The total score is calculated as a percentage, where higher scores indicate greater disability.
Patient-Specific Functional Scale (PSFS): The PSFS is an individualized PROM that allows patients to identify and rate the difficulty of specific activities limited by their musculoskeletal condition. This measure can be used across various musculoskeletal conditions and is particularly useful for evaluating functional improvement following interventions.
Pain Catastrophizing Scale (PCS): The PCS is a self-report measure designed to assess the degree to which individuals experience catastrophic thoughts and feelings related to pain. It consists of 13 items scored on a 5-point scale, with higher scores indicating greater pain catastrophizing. This PROM can be used to evaluate the psychological aspects of chronic pain in musculoskeletal conditions.
Tampa Scale for Kinesiophobia (TSK): The TSK is a self-report questionnaire designed to evaluate the fear of movement or re-injury in patients with musculoskeletal disorders. The TSK consists of 17 items, rated on a four-point Likert scale, that assess patients' beliefs about pain and movement. It is a valuable tool for identifying patients who may require additional psychological support or interventions targeting fear-avoidance behaviors in the context of musculoskeletal pain and rehabilitation.

What Makes a Fantastic PROM?

A fantastic PROM should be:

Useful for the target population (disease/region-specific vs. quality of life, constructs, or function)
Time-efficient
Patient-friendly (easy to understand and not offensive)
Cost-effective (low royalties, paper/printing costs)
Easy to score and interpret
Reliable (predictable and repeatable)
Valid for the condition (measures what it proposes to measure)
Responsive to change (detects clinically important change over time)

Choosing PROMs

COSMIN taxonomy. Note, Interpretability means scores are meaningful and able to be used in some practical manner.

Selecting an appropriate PROM can be challenging. The following steps provide a guide to find the best PROM for your needs:

Look for a Core Outcome Set: A minimal set of outcome measures recommended for clinical trials. Once a core outcome set has been agreed upon (by clinicians, scientists, patients) the hope is that all relevant studies will use it for a particular condition to enable easier comparison between studies. An example is the COMET database. Areas include pain, disability, quality of life, psychological measures, healthcare utilisation, and employment status.
Check for Systematic Reviews of PROMs: Consult the COSMIN database for PROMs with good properties (validity, reliability, responsiveness, and interpretability).
Conduct Your Own Systematic Review: If no systematic review is available, perform your own using COSMIN guidance. Balance the sense of overall quality of the PROMs vs ones that are practically useful
Perform Original Measurement/Psychometric Research: If no studies have tested the validity, reliability, and responsiveness for a given set of PROMs for a condition, you could conduct your own research.
Develop a New PROM: As a last resort, develop a new PROM instrument and test it, though this is not recommended due to the rigorous process involved and the abundance of existing PROMs.

COSMIN, or Consensus-based Standards for the selection of health Measurement INstruments, is an international initiative aimed at improving the selection of outcome measurement instruments, such as PROMs, by providing high-quality information on the measurement properties of these instruments. COSMIN offers a comprehensive database that includes systematic reviews and information about the quality of various PROMs. This initiative also develops and disseminates methodological tools and guidelines for selecting, developing, and evaluating health measurement instruments.

The Problem with PROMs

Despite their usefulness, there are several issues associated with PROMs:

Most PROMs have poor or unknown evidence for their properties, necessitating caution when using them.
Additional rigorous research is needed to validate many PROMs.
There is an overabundance of PROMs, making selection difficult.
A small selection of PROMs have been deemed good, but overall consensus is lacking.

For example a 2019 review on PROMs in orthopedic research found that PROMs with poor or unknown psychometric properties overestimate treatment effects in clinical research for rotator cuff disease by 68.4%. This is the first empirical evidence showing that variations in PROMs' quality can bias treatment effect estimates. The authors concluded that to avoid misleading decision-making, researchers and clinicians should carefully assess the quality of PROMs used in their studies and practice.^[1]

When used appropriately, outcome measurement can lead to a better understanding of disease and disability, improved evaluation of treatments, and enhanced patient care in the long term.

Conclusion

In musculoskeletal medicine, PROMs play a critical role in understanding patients' health status and the impact of treatments. While there are challenges in implementing PROMs in clinical settings, such as cost, time, and resistance to change, their benefits in improving patient care and informing clinical decision-making cannot be overstated.

Selecting the right PROMs for your practice can be a complex process, but by following the steps outlined in this article and considering factors such as validity, reliability, and responsiveness, you can make an informed choice that benefits both your patients and your practice.