Reply to: What could a new disease activity score for polymyalgia rheumatica do better?

We thank Prof. Leeb for his interest in our Review (Camellino, D., Matteson, E. L., Buttgereit, F. & Dejaco, C. Monitoring and long-term management of giant cell arteritis and polymyalgia rheumatica. Nat. Rev. Rheumatol. 16, 481–495 (2020))¹ and for his comments (Leeb, B. F. What could a new disease activity score for polymyalgia rheumatica do better? Nat. Rev. Rheumatol. https://doi.org/10.1038/s41584-020-00550-6 (2020))². As he points out, the Polymyalgia Rheumatica Activity Score (PMR-AS) is currently the only validated score for monitoring disease activity in patients with PMR³. Score calculation is straightforward, incorporating standard clinical data that captures disease features (including pain, stiffness, elevation of the upper limbs, physician’s global assessment and inflammatory indexes) relevant for the evaluation of a patient with PMR.

Despite these advantages, the PMR-AS does not seem to be widely used. On 17 October 2020, we carried out a search of studies in patients with PMR through the Clinicaltrials.gov database. Among 105 studies retrieved, seven trials explicitly included the PMR-AS among their outcomes. We also analysed the publications included in the 2015 ACR–EULAR recommendations for the management of PMR⁴. Among the nine studies on interventions published after 2004 (the year the PMR-AS was published), only one trial reported using the score⁵. Similarly, a 2020 systematic review from an OMERACT special interest group⁶ identified 13 studies using the PMR-AS out of a total of 46.

The value of a clinical index is not defined by the number of its users. It is well recognized that composite scores, which are the pillars of treat-to-target strategies in rheumatoid arthritis, are often overlooked in clinical practice owing to time constraints or to the belief that the overall impression of the physician could be sufficient to assess the patient’s state comprehensively⁷.

The aim of the OMERACT initiative is to develop core sets of measures for the evaluation of patients with rheumatic diseases⁸. In 2017, laboratory indexes, pain, stiffness and physical function were selected as candidates for the inner core of domains that should be present in every clinical trial in PMR⁹. However, high-quality evidence was not available for any of the instruments currently used to measure these domains⁶. Physical function is one of the most critical domains for patients, but the sole assessment of upper limb elevation seems insufficient to fully describe the impairment of physical function⁶. In a survey of 78 patients with PMR, the experience of stiffness and the effect of fatigue were identified as themes not adequately captured by the candidate instruments, suggesting the need for new patient-reported outcome measures¹⁰. PMR is a multifaceted disease, in which different pathophysiological manifestations can co-exist and have different clinical effects on patients. Moreover, the objective evaluation of the patient’s status might be further complicated by pre-existing conditions or by glucocorticoid-related adverse effects.

The PMR-AS is the first, and currently the only, instrument to monitor disease in patients with PMR. That notwithstanding, there is still a long road ahead before we have a comprehensive tool that can be used to objectively assess disease activity and that embraces patients’ experiences.