Radiographic assessment of hip osteoarthritis progression: impact of reading procedures for longitudinal studies

Objective-To compare radiographic reading procedures and evaluate their imp act on sample size in hip osteoarthritis (OA) longitudinal studies. Methods-Pelvic radiographs performed twice, three years apart, in 104 patie nts with hip OA were read by a single reader using the Kellgren and Lawrenc e system, joint space narrowing scale, and joint space width (JSW). Reading procedures were (a) films read as single radiographs, (b) films grouped by patient but read in random order, (c) films grouped by patient and chronol ogically ordered, all with landmarks for JSW measurements, (d) films read a s single radiographs, without landmarks for JSW measurements. JSW was measu red at the narrowest point with a 0.1 mm graduated magnifying glass. Results-More Kellgren and Lawrence or joint space narrowing grades were mod ified respectively with the single (42% and 37%) than with the paired (32% and 23%) or chronologically ordered (34% and 29%) reading procedures. Varia bility of JSW progression was principally related to mean progression (88.3 %) and landmarks (almost 10%). Standardised response means were -0.71 with the paired reading procedure with landmarks, -0.68 with the single reading procedure with landmarks, -0.65 with the single reading procedure without l andmarks. With landmarks, 10% more patients would be needed using single th an paired reading. Using single reading, 10% more patients would be needed without landmarks than with landmarks. Conclusion-Kellgren and Lawrence grading seems to be influenced by the read ing procedure, as is joint space narrowing grading, for assessing hip OA. P aired reading procedure with landmarks for JSW should be recommended in lon gitudinal studies.