B.M. de Klerk

Impact of different descriptions of the Kellgren and Lawrence classification criteria on the diagnosis of knee osteoarthritis

Objectives Although the Kellgren and Lawrence (K&L) criteria for defining radiological osteoarthritis are widely used in epidemiological and clinical studies, the authors previously documented the existence of five different versions of these criteria. This study identifies the impact of the use of alternative versions of the K&L criteria and evaluates which description has the highest association with knee complaints. Methods Two readers scored most radiographs of the knees of participants of the Rotterdam Study with the original K&L description (90%). In addition, each alternative description was used in a random part (20%) of the radiographs. The authors calculated reproducibility of all descriptions, and compared sensitivity and specificity of the alternative descriptions for three cut-off points with the original description as reference standard (K&L≥1, K&L≥2 and K&L≥3). The authors calculated κ statistics to compare agreement between the original and alternative descriptions, and evaluated the association with knee complaints. Results The dataset comprises radiographs of knees of 3071 people. For cut-off K&L≥1 all four alternatives classified more people as having osteoarthritis than the original description; κ was low, and sensitivity and specificity were moderate to good. For cut-offs K&L≥2 and K&L≥3 there was little difference in the number of cases and κ, sensitivity and specificity were good to perfect. The original description and alternative 3 showed the strongest association with knee complaints. Conclusions The different descriptions of the K&L criteria have impact on the classification of osteoarthritis in the lowest grade (K&L≥1). All descriptions have strengths and weaknesses. It depends on the purpose which is the best description.

Development of radiological knee osteoarthritis in patients with knee complaints

Objectives It is currently impossible to identify which patients with knee complaints presenting to the general practitioner will develop knee osteoarthritis (OA) pathology at a later stage. This study examines the determinants for developing OA pathology on x-ray in patients with knee complaints but no radiological OA at baseline in the painful knee. Methods Data from the prospective Rotterdam cohort study (including subjects aged ≥55 years) were used. Analysis was performed on 623 subjects with knee complaints at baseline and their data at 6-year follow-up (T1; n=607) and at 11-year follow-up (T2; n=457). At baseline, none had radiological OA (rOA=Kellgren and Lawrence (KL) grade ≥2) in the painful joint. At follow-up, predictors for rOA were determined using multivariate ordinal logistic regression analysis. Results At T1, 8.5% of the group had developed knee rOA and, by T2, this had increased to 23%. Determinants remaining significant in the multivariate analysis were female gender (OR 1.95, 95% CI 1.15 to 3.36), other joint complaints (OR 2.22, 95% CI 1.12 to 4.35) and KL grade 1 at baseline in the painful knee joint (OR 7.14, 95% CI 4.55 to 11.1). All outcomes are adjusted for all included determinants. Conclusion The best predictors of development of knee rOA are a combination of female gender, other joint complaints and KL grade 1 in the painful joint. KL grade 1 in combination with knee pain should be considered as early OA in patient management.

Factors associated with reaching 90 years of age: a study of men born in 1913 in Gothenburg, Sweden

With interest, we read the prospective study by Wilhelmsen et al. [1] about health factors associated with reaching old age. The conclusion of the study is that thereareseveralmodifiable lifestyle factorsassociatedwith reaching age 90 years inmen.We think it is a unique prospective cohort study with a long follow-up and accurate describedmethods and results. However,wehavesomequestionsremaining.

463 KNEE JOINT BONE SHAPE IS RELATED TO BMI BUT ONLY MARGINALLY TO EARLY SIGNS OF KNEE OSTEOARTHRITIS IN HEALTHY MIDDLE-AGED WOMEN

disease (LDD) as determined by MR scan is highly heritable and is positively correlated with age. We have previously reported that our longitudinal study of LDD follow-up had confirmed deterioration in LDD over 11 years in almost all subjects. We wished to determine if progression of LDD is itself mediated by genetic factors. Methods: Healthy twin volunteers forming the UK twin register (www.twinsuk.ac.uk) who had previously undergone spine MR scanning in 1996-9 were recalled for repeat sagittal T2-weighted MR scan. The new scans were coded for degenerative change using the same 4-point scale for disc height, disc signal, disc bulge and anterior osteophytes (Jarosz et al). An LDD summary score was derived by summing the codes at the 5 lumbar discs. A difference in LDD summary score was computed by taking the summary score for the baseline scan from that of the follow-up scan, and adjusting for time between the MR scans. Questionnaires were used, as at baseline, to determine demographic and lifestyle factors. In order to capture the variation inherent in the interval-adjusted change in summary score, principal components analysis (PCA) was performed (Stata 10) and heritability of the first component assessed using Mx. Results: Longitudinal data were available for 403 twins, 8 (1.9%) of whom were male. Mean (range) age at baseline = 53.3 (32.3-69.5) years. The mean (range) interval between baseline and follow-up was 10.7 (7.6-13.7) years. Almost all the MR scans deteriorated with mean LDD summary score at baseline vs follow-up = 13.1 vs 22.1 (p<0.0001). PCA of the time-adjusted change in summary score revealed that the first 2 components accounted for 63% of the variation in MRI deterioration. Heritability of the 1st component was best explained using a model containing genetic and unique environmental factors only (AE model) ie no detectable contribution from the shared family environment. The AE model estimated heritability (95% CIs) = 76 (65-83)%. Conclusions: This is the first large scale, longitudinal, population-based study of LDD in healthy adult volunteers to examine the heritability of progression of LDD. This longitudinal study may identify those that deteriorate more rapidly and who may have worse symptoms. Demonstrating a genetic component to progression leads naturally to association studies both candidate gene and genome-wide association (GWA) studies. In GWA an agnostic search of the genome would be made for variants associated with change in LDD. GWA studies have been performed with success in other complex traits and may uncover genetic variants associated with very rapid deterioration in LDD, in what is an almost universal condition. GWA studies generally require very large sample sizes and refined or enriched phenotyping methods. Using this information on heritability of LDD progression we will be able to optimise our GWA strategy to search for variants influencing LDD progression.