Sjogren's Syndrome Classification

Ultrasound Improves Sjogren's Syndrome Classification
By David Douglas
May 03, 2014

NEW YORK (Reuters Health) - Salivary gland ultrasonography (SGUS) enhances American College of Rheumatology (ACR) classification of patients with Sjögren's syndrome (SS) and in the future should be included in evaluations, according to French investigators.

"In this study, we confirm that salivary gland ultrasonography has a large clinical impact for the diagnosis of primary Sjögren's syndrome," Dr. Divi Cornec told Reuters Health by email. "This non-invasive, easily accessible tool should be included in the diagnostic work-up for suspected Sjögren's syndrome. An international study group has been recently created to definitely validate the procedure."

In an April 4th online paper in Rheumatology, Dr. Cornec of Hopital de la Cavale Blanche, Brest and colleagues note that in 2012, the ACR issued new classification criteria for SS. These were selected based on expert opinion but none reflects salivary gland function and morphology, which are altered in SS.

To examine the utility of SGUS in augmenting the diagnostic performance of the ACR approach, the researchers examined 101 patients with suspected SS. Among inclusion criteria were subjective ocular or oral dryness, recurrent or bilateral parotidomegaly or laboratory abnormalities suggesting SS. An SGUS echostructure score of 2 or more was considered abnormal.

All cases were reviewed by a panel of three experts blinded to the SGUS findings and SS was diagnosed in 45 patients. Similar proportions of patients with and without SS had an ocular staining score at or beyond 3.

As covered in the ACR classification criteria, adding rheumatoid factor positivity and an antinuclear antibody titer of 1.320 or more as an alternative to anti-SSA/SSB positivity increased the sensitivity of the serological item without modifying specificity compared with using anti-SSA/SSB alone.

SGUS alone gave a sensitivity of 60.0% and a specificity of 87.5%. Adding the SGUS score to the ACR criteria increased the sensitivity from 64.4% to 84.4% and only "slightly" decreased specificity, from 91.1% to 89.3%.

SGUS, say the researchers, "is simple, non-invasive, widely available, non-irradiating and less expensive than other imaging techniques." Adding it "substantially improved the diagnostic performance of the 2012 ACR criteria set."

Thus they conclude that SGUS "should be included in future consensual classification criteria for SS."

SOURCE: http://bit.ly/R825Kg

Rheumatology 2014.


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SUPERSONIC SHEAR IMAGING in MSK SYSTEM

Dear Editor,

The skeletal muscle is an anisotropic, viscoelastic, and complex passive and active tissue. Therefore, the in vivo evaluation of the biomechanical properties of the skeletal muscle is a complex issue. A new ultrasound-based technique, supersonic shear imaging (SSI), can be used to quantify soft tissue stiffness [1]. 

Supersonic shear imaging is based on the conventional ultrasound probe, which induces an ultrasonic radiation force deep within the muscle. Propagation of the resulting shear waves is then imaged with the same probe at an ultra-fast frame rate. The shear elasticity of a tissue can be mapped quantitatively from this propagation movie. This approach may provide a complete set of quantitative and in vivo parameters describing biomechanical properties of the skeletal muscle [2]. Recent studies have shown excellent intra- and interobserver reliability of the muscle shear elastic modulus measured by SSI [3,4]. Several studies also imply that SSI is a promising tool for evaluating muscle conditions because it may provide an indirect estimation of passive muscle force [5]. It may also provide a more accurate estimation of individual muscle force, compared to surface electromyography [6]. Different pathologies of the skeletal muscle (e.g., muscle fibrosis, muscular dystrophy, and spasticity in upper motor neuron diseases) may change the muscle shear elastic modulus. Thus, SSI may contribute to the improved diagnosis and management of neuromuscular and orthopedic diseases. However, a few considerations should be addressed.

First, all current studies have investigated healthy participants. The diagnostic value of SSI in patients should be further studied.

Second, few studies have focused on the tendon in which pathological changes may interfere with muscle function. The tendon has a much higher elastic modulus and smaller volume in comparison to the muscle, which makes SSI challenging for examining tendinopathy.   

Third, because skeletal muscle is compressible, variations of the probe pressure on the muscle may cause different shear elastic modulus. The higher pressure on the muscle, the higher is shear elastic modulus. A very light contact between the probe and the skin is recommended when examining muscle elasticity.

Fourth, the region of interest (ROI) in SSI for obtaining shear elastic modulus is circular. Therefore, its representation of an entire muscle is questionable. A standardized surface landmark and the depth of ROI should be clearly described. The average of the data from multiple ROIs may be calculated to minimize measurement errors.

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MUSCULOSKELETAL APPLICATIONS of SUPERSONIC  SHEAR IMAGING

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