Has MRI an Added Value over Serum Creatine Kinase Measurement in Myositis?

Nicolo Pipitone¹, Antonella Notarnicola², Giulio Zuccoli³, Lucia Spaggiari⁴, Gabriele Levrini⁵, Arnaldo Scardapane⁶, Florenzo Iannone², Giovanni Lapadula² and Carlo Salvarani¹, ¹Rheumatology Unit, Arcispedale S Maria Nuova, Reggio Emilia, Italy, ²D.I.M.I.M.P, Rheumatology Unit - University of Bari, Bari, Italy, ³Children's Hospital of Pittsburgh, Pittsburgh, PA, ⁴Radiology, Arcispedale S Maria Nuova, Reggio Emilia, Italy, ⁵Arcispedale S Maria Nuova, Reggio Emilia, Italy, ⁶Radiology, University of Bari, Bari, Italy

Meeting: 2014 ACR/ARHP Annual Meeting

Keywords: MRI and myositis

Session Information

Title: Muscle Biology, Myositis and Myopathies: Immunological Aspects of Inflammatory Myopathy

Session Type: Abstract Submissions (ACR)

Background/Purpose

MRI is widely used to assess inflammation in myositis. Muscle edema on short tau inversion recovery (STIR) sequences is thought to reflect active inflammation. However, it is unclear whether MRI has an added value over the cheaper, easier-to-obtain measurement of serum creatine kinase (sCK) levels. Our aim was to assess the concordance between sCK and MRI edema in a cohort of patients with myositis at their first presentation to our centers.

Methods

We enrolled in 2 Rheumatology centers 73 patients, 34 with dermatomyositis (DM) and 39 with polymyositis (PM) diagnosed according to Bohan and Peter criteria. In all patients, sCK were measured and MRI sequences were acquired at the same time. MRI edema (1= present, 0= absent) was assessed bilaterally in 17 thigh and pelvic floor muscles. An MRI composite edema score (0-17) was calculated by adding the separate scores bilaterally and dividing them by two as described elsewhere (1). sCK was considered positive if values were above the upper limit of normal (190 U/l), while MRI was considered positive if the edema score was at least 1. The (single measures) intraclass correlation coefficient (ICC) between the Radiologists involved was 0.78. Muscle strength was measured by MMT (manual muscle testing) and graded according to the Medical Research Council extended scale (0-5). The ICC between the 2 physicians performing the MMT was 0.8.

Results

sCK and MRI were discordant in 47% of patients with myositis, more frequently in DM (59%) than in PM (39%). 56% of patients with DM, but only 15% of those with PM had a positive MRI with normal sCK.

	All patients (=73)	DM (=34)	PM (=39)
sCK+ MRI+	32	11	21
sCK- MRI-	7	3	4
sCK + MRI-	9	1	8
sCK- MRI+	25	19	6

There was a significant correlation between MRI score and muscle strength of the hip flexors (Spearman’s rho 0.26, p 0.028) but not between MRI score and overall muscle strength.

Conclusion

MRI is a useful tool to assess disease activity in myositis, especially in DM, where it can be identify a sizeable number of patients who have normal sCK. Further studies of larger cohorts are warranted to confirm our findings.

References: (1) Clin Exp Rheumatol 2012; 30:570-3

Disclosure:

N. Pipitone,
None;

A. Notarnicola,
None;

G. Zuccoli,
None;

L. Spaggiari,
None;

G. Levrini,
None;

A. Scardapane,
None;

F. Iannone,
None;

G. Lapadula,
None;

C. Salvarani,

Novartis Pharma AG,

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