Background/Purpose:

Polymyalgia rheumatica (PMR) is a frequent inflammatory condition in elderly people. The place of imaging becomes important for positive and differential diagnosis like malignancy but there is no gold standard. We compared ¹⁸f-Fluoro-Dexoxyglucose Positron Emission Tomography (FDG-PET/CT) findings in patients with PMR and controls without rheumatologic disease.

Methods:

Forty-six patients with a diagnosis of PMR, according to 2012 ACR/ EULAR criteria, who have had a FDG-PET/CT have been included. For comparison, fifty-tree patients who have had a FDG-PET/CT for initial staging or follow-up of neoplasm were included as controls. 17 sites where analyzed on PET: 2 shoulders, 2 acromio-clavicular and 2 sterno-clavicular joints, 2 greater trochanters, 2 hips, 2 ischial tuberosities, 2 iliopectinal bursitis, 2 pubic symphysis enthesis and only the interspinous space with the most FDG uptake. We used the semi-quantitative scoring system, by Goerres and al. to evaluate visually FDG uptake (0 to 3 compared to liver uptake) into these sites. We calculated the FDG uptake score corresponding to the mean of intensity over all sites,  and the number of sites with significant uptake (FDG uptake 2 or 3) for each patient.

Results:

The two groups were comparable for the median patient age (68,9

for PMR vs. 68,1 years for controls). The characteristics of the patients of PMR group were 55% women, CRP 40,9mg/L, ESR 41,1mm, and an ACR/EULAR score without ultrasound of 4.78/6. Significant differences between the two groups were found for FDG uptake score and for number of sites with significant uptake (Table 1): 1.09 vs. 0.34, and 6.13 sites vs. 1.49 sites, p<0.0001.

With ROC curves analysis, we show that the presence of 3 or more sites with significant uptake is correlated with the diagnosis of PMR with 72% sensibility, 79% specificity [OR = 9.69]. For the FDG uptake score the cut off is 0.53 [Se 76%, Sp 79%; OR 12.1].

We found significant differences in all sites analyzed separately for FDG uptake score and number of sites with significant uptake compared to controls, particularly marked for shoulders, ischial tuberosities and interspinous bursitis (p<0.00001 for FDG uptake score).

Table 1.

Conclusion:

FDG-PET/CT for PMR diagnosis is useful: we found significant uptake in articular and peri-articular sites compared to controls particularly shoulders, ischial tuberosities and interspinous space. We propose the number of 3 sites with significant uptake and a FDG uptake score over 0.53 as cut-offs for the diagnosis of PMR.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/contribution-of-18f-fluoro-dexoxyglucose-positron-emission-tomography-for-the-diagnosis-of-polymyalgia-rheumatica-a-controlled-study/