Assessment of inflammatory myositis

Reliability of histographic analysis for paraspinal muscle degeneration in patients with unilateral back pain using magnetic resonance imaging

BACKGROUND

Mixed use of T1- or T2-weighted magnetic resonance imaging (MRI) in histographic analysis has impeded cross-reference of studies on fatty degeneration of muscles in patients with back pain.

OBJECTIVE

The current study aimed to establish the measurement reliability of histographic analysis for normal and painful paraspinal muscles between T1- and T2-weighted MRI.

METHODS

T1- and T2-weighted MRI at the L4-5 level were performed in 31 patients with unilateral back pain. Two raters conducted the histographic analysis on 2 separate occasions. Multifidus, erector spinae, and psoas major muscles were assessed on both normal and painful sides.

RESULTS

Intra- and interrater reliability of the parameters were generally excellent for both T1- (intrarater: 0.83 ± 0.13 and interrater: 0.93 ± 0.08) and T2-weighted images (intrarater: 0.93 ± 0.12 and interrater: 0.92 ± 0.12). Histogram width was fair to good for both kinds of image. Intraclass correlation coefficients were similar between painful and normal sides.

CONCLUSIONS

The evidence that most histographic analysis parameters had excellent reliability for both T1- and T2-weighted images allows for cross-reference of the results between the two kinds of image. Moreover, the results of this study support the availability of histographic analysis for assessment of fatty degeneration in patients with back pain.

Laboratory testing in the diagnosis and management of idiopathic inflammatory myopathies

Laboratory testing commonly used to assess the idiopathic inflammatory myopathies (IIMs) can be divided into three categories: (1) measurement of serum activities or concentrations of muscle-derived factors--such as enzymes, myoglobin, and other molecules--in order to assess muscle injury; (2) immunologic tests that detect markers of the disease process, including serum autoantibodies that have been associated with myositis; and (3) general laboratory tests that are used to assess the patient's general status and medical condition. The laboratory assessment of muscle-derived factors that reflect muscle injury, and the determination of serum autoantibodies, play valuable roles in the diagnosis and management of the IIM. Enzyme elevations do not correlate with disease activity in all patients, however, and they must be interpreted within the clinical context. Autoantibodies can identify disease subsets with distinctive patterns of clinical manifestations, genetics, responses to therapy and prognosis, but disease-specific autoantibodies are present in only half of patients with IIM. Recent studies have defined additional myositis autoantibodies that may improve our capacity to diagnose and manage the IIM.