Stratified primary care for adults with musculoskeletal pain: the STarT MSK research programme including RCTs
Authors: Foster Nadine E , Dunn Kate M , Protheroe Joanne , Hill Jonathan C , Lewis Martyn , Saunders Benjamin , Jowett Sue , Hennings Susie , Campbell Paul , Bromley Kieran , Bartlam Bernadette , Babatunde Opeyemi , Wathall Simon , Oppong Raymond , Kigozi Jesse , Chudyk Adrian 
Published: July 2023

Background
Usual primary care for patients with musculoskeletal pain varies widely and treatment outcomes are suboptimal. Stratified care involves targeting treatments according to patient subgroups, in the hope of maximising treatment benefit and reducing potential harm or unnecessary interventions. This programme developed a new prognostic stratified primary care approach, where treatments are matched to a patient’s risk of future persistent pain and disability based on a prognostic tool, and compared this with usual care.

Objectives
In four linked work packages, we refined and validated a prognostic tool [the Keele STarT MSK (Subgrouping for Targeted Treatment for Musculoskeletal pain) Tool] to identify risk of poor outcome and defined cut-off scores to distinguish patient risk subgroups (work package 1); defined and agreed new matched treatment options for each risk subgroup and developed a support package for delivery of stratified care (work package 2); tested the feasibility of delivering the stratified approach through a pilot randomised controlled trial and externally validated the prognostic tool (work package 3); and tested the effectiveness of the approach by comparing the clinical effectiveness and cost-effectiveness of stratified primary care with that of usual care through a cluster randomised controlled trial with embedded health economic and qualitative studies (work package 4).

Setting
General practices and linked musculoskeletal services in the West Midlands of England, UK.

Participants
Adults registered with participating practices consulting with back, neck, shoulder, knee or multisite musculoskeletal pain, and clinicians involved in managing these patients.

Design
The programme included the following work packages: work package 1 – a prospective cohort study in 12 practices; work package 2 – an evidence synthesis, consensus group workshops and qualitative studies; work package 3 – a cluster feasibility and pilot trial in eight practices; and work package 4 – a main cluster randomised controlled trial in 24 practices, with health economic analyses and process evaluation.

Interventions
Stratified care comprised training general practitioners to use the tool and match patients to treatment options depending on their risk subgroup. Usual care comprised usual non-stratified primary care without formal stratification tools.

Main outcome measures
Cohort primary end points included function (Short Form questionnaire-36 items physical component score) and pain intensity (numerical rating scale). The trial primary end point for patient outcomes was pain intensity (monthly for 6 months) (0–10 numerical rating scale). An audit of primary care electronic medical records evaluated the impact of stratified care on clinical decision-making regarding patient management.

Results
Work package 1 – the cohort study (n = 1890 patients) refined and validated a new 10-item tool with which to stratify patients with the five most common musculoskeletal pain presentations. The tool subgroups patients into three strata with different characteristics and prognoses. Work package 2: 17 treatment options were recommended – four for patients at low risk, 10 for patients at medium risk and 15 for patients at high risk. Work package 3: the feasibility and pilot trial included 524 patients, and the learning led to amendments to several tool items and a reduced set of treatments (14 in total). Work package 4: in the main trial, 1211 patients consented to data collection (534 in stratified care, 677 in usual care). Stratified primary care did not lead to statistically significant differences in the primary patient outcome of pain intensity [stratified care mean 4.4 (standard deviation 2.3) vs. usual care mean 4.6 (standard deviation 2.4); adjusted mean difference –0.16, 95% confidence interval –0.65 to 0.34; p = 0.535]. Where differences were observed, these were largely isolated to patients at high risk of poor outcome (the smallest subgroup), in favour of stratified care. Positive differences were, however, observed in general practitioner clinical decision-making, with increased provision of written self-management information and referrals to physiotherapy, plus reductions in prescription medication. The economic evaluation demonstrated that costs of care were similar across trial arms (£6.85, 95% confidence interval –£107.82 to £121.54 more for stratified care), with incremental quality-adjusted life-years of 0.0041 (95% confidence interval –0.0013 to 0.0094), representing a net quality-adjusted life-year gain. Stratified care was associated with an incremental cost-effectiveness ratio of £1670 per additional quality-adjusted life-year gained. At a willingness-to-pay threshold (λ) of £20,000 per quality-adjusted life-year, the incremental net monetary benefit was £132 and the probability of stratified care being cost-effective was approximately 73%. The very small differences suggest caution in the interpretation of this result. The qualitative findings revealed that general practitioners felt stratified care had a positive role in informing clinical decision-making, helped them to give greater attention to psychosocial issues and take a more functional approach, and facilitated negotiations with patients about treatment options such as imaging.

Limitations
The randomised controlled trial was not powered to detect differences between stratified and usual care for patients in each risk subgroup (low, medium and high) nor with each different musculoskeletal pain presentation. The stratified care electronic medical record template ‘fired’ only once per patient.

Conclusions
The Keele STarT MSK Tool is a valid instrument with which to discriminate between, and predict outcomes of, primary care patients with musculoskeletal pain. Although the randomised trial showed no significant benefit in patient-reported outcomes compared with usual care, some aspects of clinical decision-making improved and the approach was cost-effective.

Future work
The Keele STarT MSK Tool has been shared with over 1000 tool license requestees, leading to other work. Trial data sets have also led to other work, developing personalised prognostic models for back and neck pain patients (the European Union-funded Back-UP project). The challenge remains how to improve outcomes for primary care patients with musculoskeletal pain.

Trial registration
This trial is registered as ISRCTN15366334.

Funding
This project was funded by the National Institute for Health and Care Research (NIHR) Programme Grants for Applied Research programme and will be published in full in Programme Grants for Applied Research; Vol. 11, No. 4. See the NIHR Journals Library website for further project information.