Predicting persistent inflammatory arthritis amongst early arthritis clinic patients in the UK: is musculoskeletal ultrasound required?

Abstract

Introduction: Analyses of large clinical datasets from early arthritis cohorts permit the development of algorithms that may be used for outcome prediction in individual patients. The value added by routine use of musculoskeletal ultrasound (MSUS) in an early arthritis setting, as a component of such predictive algorithms, remains to be determined.

Methods: The authors undertook a retrospective analysis of a large, true-to-life, observational inception cohort of early arthritis patients in Newcastle upon Tyne, UK, which included patients with inflammatory arthralgia but no clinically swollen joints. A pragmatic, 10-minute MSUS assessment protocol was developed, and applied to each of these patients at baseline. Logistic regression was used to develop two "risk metrics" that predicted the development of a persistent inflammatory arthritis (PIA), with or without the inclusion of MSUS parameters.

Results: A total of 379 enrolled patients were assigned definitive diagnoses after ≥12 months follow-up (median 28 months), of whom 162 (42%) developed a persistent inflammatory arthritis. A risk metric derived from 12 baseline clinical and serological parameters alone had an excellent discriminatory utility with respect to an outcome of PIA (area under receiver operator characteristic (ROC) curve 0.91; 95% CI 0.88 to 0.94). The discriminatory utility of a similar metric, which incorporated MSUS parameters, was not significantly superior (area under ROC curve 0.91; 95% CI 0.89 to 0.94). Neither did this approach identify an added value of MSUS over the use of routine clinical parameters in an algorithm for discriminating PIA patients whose outcome diagnosis was rheumatoid arthritis (RA).

Conclusions: MSUS use as a routine component of assessment in an early arthritis clinic did not add substantial discriminatory value to a risk metric for predicting PIA.

Figure 1

Risk metric calculation tool (MSUS not required). Risk metric calculation tool for use in clinical practice, in which MSUS is not required.

Figure 2

ROC curve comparing discriminatory utility of predictive metrics for persistent inflammatory arthritis. Receiver operator characteristic (ROC) curve illustrating the discriminatory utility of two risk metrics, derived excluding or incorporating musculoskeletal ultrasound (MSUS) parameters, with respect to an outcome of PIA ("No MSUS" and "MSUS" respectively; area under both curves 0.91; SEM 0.015; P < 0.001).

Figure 3

Risk metric calculation tool (includes MSUS parameter). Revised risk metric calculation tool for use in clinical practice, derived from baseline variables that included musculoskeletal ultrasound (MSUS) parameters; an assessment of grey-scale synovitis is a required component of the resultant risk metric.

Figure 4

ROC curve comparing discriminatory utility of predictive metrics for RA amongst PIA sub-cohort. Receiver operator characteristic (ROC) curve illustrating the discriminatory utility of two risk metrics derived amongst the PIA sub-cohort alone, excluding or incorporating musculoskeletal ultrasound (MSUS) parameters, with respect to an outcome of rheumatoid arthritis (RA) ("No MSUS" and "MSUS" respectively). Area under curves: 0.93 (No MSUS; SEM 0.021; P < 0.001), 0.89 (MSUS; SEM 0.025; P < 001).