title: Assessing smallest detectable change over time in continuous structural outcome measures: application to radiological change in knee osteoarthritis.
abstract: Interpreting changes in continuous structural outcome measures is a common problem in clinical research and in daily practice. We propose a method for estimating whether difference observed between two successive measures in an individual constitutes a statistically relevant change or a change induced by variability. This statistically relevant change is based on an analysis of reproducibility. The continuous structural outcome measure investigated as an example was joint space width (JSW) measurement on standard X-rays, which is known to be the primary end-point for assessing structural osteoarthritis progression. The results of the present study demonstrate that cutoffs are closely dependent on all sources of variabilities in JSW measurement such as joint positioning, radiographic procedure, and the measurement process itself. Therefore, we suggest to determine cutoffs for each study using a representative sample of the population studied and using the procedures and methods of measurement of the specific study. This approach may easily be extended to other continuous structural outcome measures.
authors.affiliation: Clinique de Rhumatologie, Hôpital Cochin et Université René Descartes, Paris, France.
authors.forename: P
authors.initials: P
authors.lastname: Ravaud
authors.forename: B
authors.initials: B
authors.lastname: Giraudeau
authors.forename: G R
authors.initials: GR
authors.lastname: Auleley
authors.forename: R
authors.initials: R
authors.lastname: Edouard-Noël
authors.forename: M
authors.initials: M
authors.lastname: Dougados
authors.forename: C
authors.initials: C
authors.lastname: Chastang
mesh_terms: D000368:Aged; D000886:Anthropometry / Q000379:methods*; D001175:Arthrography; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D015588:Observer Variation; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging*; D017063:Outcome Assessment, Health Care; D015203:Reproducibility of Results; D013997:Time Factors