Validity of the polymyalgia rheumatica activity score in primary care practice

To evaluate the validity and reliability of the polymyalgia rheumatica (PMR) activity score (PMR-AS) for relapse diagnosis by general practitioners (GPs) who manage a large proportion of patients with PMR.

Seven clinical vignettes of PMR were used, for which 35 rheumatologists previously made a diagnosis of relapse or no relapse with greater than 80% agreement. These vignettes were submitted to 163 GPs, who were asked to assess disease activity using a visual analogue scale (VASph), this being the only physician-dependent component of the PMR-AS. The 1116 available vignette-GP combinations were used to assess differences in VASph assessed by GPs versus rheumatologists. Statistical associations linking a relapse diagnosis by the rheumatologists (the reference standard) to the value of the GP-assessed PMR-AS or its components (GP-assessed VASph, visual analogue scale pain score, C-reactive protein, morning stiffness and elevation of upper limbs) were evaluated.

No significant differences were found between VASph scores by GPs versus rheumatologists for any of the vignettes. A relapse diagnosis was strongly associated with PMR-AS values of 7 or more (sensitivity 99.4%; specificity 93.3%; agreement 95.9% (95% CI 94.5% to 97.0%) with kappa = 0.92). Of the 590 GP-vignette combinations with PMR-AS values lower than 7, all but three (0.5%) had no relapse diagnosis. Of 510 combinations with PMR-AS values of 7 or more, only 42 (8%) had no flare diagnosis.

This study supports the validity of the PMR-AS in primary care practice and provides evidence that a good scoring system can be useful to guide clinical and therapeutic decisions.