Background/Purpose: Accurate determination of disease activity in polymyalgia rheumatica(PMR) is challenging due to the subjective nature of symptoms and concurrent musculoskeletal complaints in an elderly population.Any biomarker than assists physicians in more accurately determining patients disease state, thereby enabling safe adjustment of steroid dose would be welcomed. Previously we have demonstrated the enhanced specificity of plasma fibrinogen over both ESR and CRP for the detection of response to treatment in patients with active PMR. We sought to prospectively evaluate the utility of the biomarkers ESR, CRP and Fibrinogen for identifying different disease states in patients with known PMR.

Methods:

Patients with PMR were divided into high/moderate disease activity(Group 1) or low disease activity(Group 2) according to the Polymyalgia Rheumatica Activity Score(PMR-AS) as per Bird and Leeb. PMR-AS =CRP(mg/dl)+ VAS pain(0-10 scale)+ VASphysician (0-10scale)+Morning stiffness([min]x.1)+ Upper Limb Elevation(0-3 scale). A PMR-AS > 7 indicates medium/high disease activity with a PMR-AS < 7 indicating low disease activity. Plasma fibrinogen, CRP and ESR were also assayed. An ESR value of 30mm/hr(lab normal<20mm/hr) and CRP of 6mg/L (lab normal<5mg/l) were considered the upper limit for detection of low disease activity. The upper limit of the lab normal for Fibrinogen (4g/L) was used. Sensitivity, specificity, positive predictive values and likelihood ratios were calculated for all biomarkers.

Results: Data was available from 120 patient visits. Demographic data was similar in both groups. Mean age was 71.8 years. All patients were receiving glucocorticoids with a median steroid dose of 10mg in Group 1 and 5mg in Group 2.There were significant differences in steroid dose between the two groups(p<.001). 70 patients were defined as having low disease activity as per the PMR-AS.  Of these 64/70 had a normal plasma fibrinogen with 56/70 having an ESR <30mm/hr and 45/70 a CRP < 6mg/L. Table 1 shows the specificity, sensitivity, positive predictive values and likelihood ratios for the biomarkers as calculated for all 120 patient visits.

Overall plasma fibrinogen was more specific than either ESR or CRP for differentiating between low disease activity and moderate/high disease activity in PMR. It also demonstrated a better positive predictive value and likelihood ratio than the standard biomarkers ESR and CRP for identifying patients with moderate/high disease activity.

Conclusion:

Plasma fibrinogen can aid treating physicians in determining disease activity in PMR. An elevated plasma fibrinogen level more accurately indicates that patients are in a moderate or highly active disease state than either the ESR or CRP alone. Measurement of fibrinogen as an adjunct to ESR and CRP in patients with PMR can help treating physicians more accurately identify patients’ disease status and guide decisions with regards glucocorticoid dosage.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/plasma-fibrinogen-is-an-accurate-marker-of-disease-activity-in-patients-with-polymyalgia-rheumatica/