Systematic review of the concurrent and predictive validity of MRI biomarkers in OA

Evolution of semi-quantitative whole joint assessment of knee OA: MOAKS (MRI Osteoarthritis Knee Score)

OBJECTIVE

In an effort to evolve semi-quantitative scoring methods based upon limitations identified in existing tools, integrating expert readers' experience with all available scoring tools and the published data comparing the different scoring systems, we iteratively developed the magnetic resonance imaging (MRI) Osteoarthritis Knee Score (MOAKS). The purpose of this report is to describe the instrument and its reliability.

METHODS

The MOAKS instrument refines the scoring of bone marrow lesions (BMLs) (providing regional delineation and scoring across regions), cartilage (sub-regional assessment), and refines the elements of meniscal morphology (adding meniscal hypertrophy, partial maceration and progressive partial maceration) scoring. After a training and calibration session two expert readers read MRIs of 20 knees separately. In addition, one reader re-read the same 20 MRIs 4 weeks later presented in random order to assess intra-rater reliability. The analyses presented here are for both intra- and inter-rater reliability (calculated using the linear weighted kappa and overall percent agreement).

RESULTS

With the exception of inter-rater reliability for tibial cartilage area (kappa=0.36) and tibial osteophytes (kappa=0.49); and intra-rater reliability for tibial BML number of lesions (kappa=0.54), Hoffa-synovitis (kappa=0.42) all measures of reliability using kappa statistics were very good (0.61-0.8) or reached near-perfect agreement (0.81-1.0). Only intra-rater reliability for Hoffa-synovitis, and inter-rater reliability for tibial and patellar osteophytes showed overall percent agreement <75%.

CONCLUSION

MOAKS scoring shows very good to excellent reliability for the large majority of features assessed. Further iterative development and research will include assessment of its validation and responsiveness.

Progression of lumbar disc degeneration over a decade: a heritability study

OBJECTIVES

Lumbar disc degeneration (LDD) is prevalent, age-related and contributes to low back pain. Cross-sectional LDD as determined by MRI scan is known to be highly heritable. The authors postulated that the rate of progression might also be controlled by genetic factors.

METHODS

A 10-year follow-up of MRI-determined LDD was performed in 234 pairs of twin volunteers in the UK and Australia, comprising 90 monozygotic pairs and 144 dizygotic same-sex twin pairs. Of the total sample, 95% were female. The mean age at baseline was 53.3 years (range 32.3-69.5). The rate of progression was calculated and, because the effect of age was non-linear, the sample was divided into age strata and heritability estimated for each trait's progression.

RESULTS

All MRI-determined traits worsened significantly over the period of follow-up (p<0.0001 for each). Change in disc height was not heritable at any age while posterior disc bulge was heritable across all age categories (range 28-53%), with higher heritability in those over 60 years. Change in disc signal intensity and anterior osteophytes were found to be heritable only in those aged under 50 years at baseline (heritability estimates 76% (95% CI 44% to 100%) and 74% (42% to 100%), respectively).

CONCLUSIONS

Longitudinal change in LDD traits is heritable for all traits except disc height, but there is a significant influence of age, which varies across traits. Future studies to define the genetic variants influencing LDD progression should examine MRI traits individually and in women should focus on those under 50 years of age.

Summary and recommendations of the OARSI FDA osteoarthritis Assessment of Structural Change Working Group

OBJECTIVE

The Osteoarthritis Research Society International initiated a number of working groups to address a call from the US Food and Drug Administration (FDA) on updating draft guidance on conduct of osteoarthritis (OA) clinical trials. The development of disease-modifying osteoarthritis drugs (DMOADs) remains challenging. The Assessment of Structural Change (ASC) Working Group aimed to provide a state-of-the-art critical update on imaging tools for OA clinical trials.

METHODS

The Group focussed on the performance metrics of conventional radiographs (CR) and magnetic resonance imaging (MRI), performing systematic literature reviews for these modalities. After acquiring these reviews, summary and research recommendations were developed through a consensus process.

RESULTS

For CR, there is some evidence for construct and predictive validity, with good evidence for reliability and responsiveness of metric measurement of joint space width (JSW). Trials off at least 1 and probably 2 years duration will be required. Although there is much less evidence for hip JSW, it may provide greater responsiveness than knee JSW. For MRI cartilage morphometry in knee OA, there is some evidence for construct and predictive validity, with good evidence for reliability and responsiveness. The responsiveness of semi-quantitative MRI assessment of cartilage morphology, bone marrow lesions and synovitis was also good in knee OA.

CONCLUSIONS

Radiographic JSW is still a recommended option for trials of structure modification, with the understanding that the construct represents a number of pathologies and trial duration may be long. MRI is now recommended for clinical trials in terms of cartilage morphology assessment. It is important to study all the joint tissues of the OA joint and the literature is growing on MRI quantification (and its responsiveness) of non-cartilage features. The research recommendations provided will focus researchers on important issues such as determining how structural change within the relatively short duration of a trial reflects long-term change in patient-centred outcomes.