While the newly proposed polymyalgia rheumatica classification criteria will likely facilitate future research, it is important to emphasize that they are provisional and not diagnostic, Dr. Robert F. Spiera and Dr. Rene Westhovens said in an accompanying editorial.
The point that classification criteria are useful for defining patient groups for studies but are not intended to define diagnoses in clinical practice is particularly relevant in PMR, a syndrome that is "common, eminently treatable, and most often initially encountered by and treated by primary care providers rather than rheumatologists," they wrote (Arthritis Rheum. 2012;64:955-7).
As such, the criteria will undoubtedly be looked at by clinicians in practice, therefore, their performance in terms of sensitivity and specificity must be well understood and considered, they said.
The sensitivity of the scoring algorithm developed for classifying patients as having PMR in this study was 68%. Since PMR can be a very vague syndrome, and since corticosteroid treatment is generally very beneficial in patients with PMR, relying on these provisional classification criteria to determine which patients should receive treatment would could leave about a third of patients untreated and left with unnecessary suffering, Dr. Spiera explained in an interview.
He likened the diagnosis of PMR – a "difficult to define syndrome of inflammatory pain and stiffness in older people" – with U.S. Supreme Court Justice Potter Stewart’s 1964 attempt to define pornography: "... I could never succeed in intelligibly doing so, but I know it when I see it," Justice Stewart said.
Similarly, with PMR, most clinicians know it when they see it.
"Although the authors indicate the dangers of overdiagnosis of this condition because of the potential of overusing corticosteroids, when used judiciously in relatively low doses with appropriate attention to the management of comorbidities, this therapy can have very favorable risk-benefit profile," he and Dr. Westhovens wrote.
They noted that another factor limiting the generalizability of the criteria is the inclusion of elevated sedimentation rate and/or CRP; in practice, as many as 20% of patients with "fairly classic" PMR have no such elevations.
The criteria would appropriately exclude a patient without an elevated sedimentation rate and/or CRP from inclusion in a clinical trial, but in practice this shouldn’t preclude the use of corticosteroids, Dr. Spiera said.
"Although these criteria afford clinicians a basis for more objectively examining their diagnosis, and while allowing for a greater precision than Justice Stewart’s definition of pornography, they cannot yet be assured to supersede the importance of clinical sense to which that rather vague definition speaks," he and Dr. Westhovens concluded.
Dr. Spiera is director of the vasculitis and scleroderma program at the Hospital for Special Surgery, N.Y. He disclosed that he is conducting an investigator-initiated PMR drug trial supported by Roche/Genentech. Dr. Westhovens is with University Hospital Katholieke Universiteit Leuven, Belgium.
