SAT0683 NORMATIVE DATA FOR THE DISEASE AND TREATMENT ASSOCIATED KNOWLEDGE SCORE (DATAK-RA) IN PATIENTS WITH RHEUMATOID ARTHRITIS
Authors: Lisanne Renskers, Martijn Oude Voshaar, Marieke J de Jonge, Sanne Aa Rongen-van Dartel, Anita M P. Huis, Mart van de Laar, Piet L.C.M. van Riel
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background:</h3> Having adequate disease-related knowledge is essential for patients with RA, since it may influence treatment decisions, shared-decision making, and the ability to perform self-management behavior. Patient Knowledge Questionnaires can be used to measure disease-related knowledge. We recently developed and validated the item response theory (IRT) based Disease and Treatment associated Knowledge in Rheumatoid Arthritis (DataK-RA) item bank, containing 42 multiple-choice items. In the present study we establish normative data to facilitate the interpretability of DataK-RA scores. <h3>Objectives:</h3> To produce normative data for DataK-RA (IRT)-scores, stratified by sex and educational level. <h3>Methods:</h3> Consecutive patients recruited from three hospitals in the Netherlands were asked to complete a form containing either 27 or 26 DataK-RA items. Datak-RA IRT-scores and standard errors (SEs) were obtained using the weight maximum likelihood estimator. The Dutch Committee on Tests and Testing (COTAN) quality criteria for test norms were followed. DataK-RA IRT scores and the precision of the scores (SE) were summarized using the mean (SD) or median and 1<sup>st</sup> – 3<sup>th</sup> quartile in case of non-normal distribution. Scores were compared between male and female patients and patients with low, middle and high educational attainment, according to the International Standard Classification of Education, using One-way ANOVA with a significance level of α = 0.05. <h3>Results:</h3> In total 631 patients participated, most of them were female (60.9%). Mean age (SD) was 64.0 (11.6) years. Mean (SD) DataK-RA score was 52.5 (14.1) (range 11.7 – 104.7). Female patients had significantly higher Datak-RA scores compared with men (<i>F</i> = 25.23, p &lt; 0.01). Mean (SD) DataK-RA-score was 54.6 (15.1) for women, and 48.9 (11.5) for men. The median (1<sup>st</sup> – 3<sup>th</sup> quartile) SE of the IRT-scores was 4.7 (4.1 – 5.8). Regarding education, higher-educated patients had a significant higher IRT-score than middle- and lower-educated patients (p &lt; 0.01), as well as middle-educated versus lower-educated patients (p &lt; 0.01). Table 1 shows the percentiles DataK-RA-scores, and DataK-RA scores stratified by age educational level. <h3>Conclusion:</h3> We present normative data for DataK-RA scores generated from a sample of consecutive patients participating in an ongoing longitudinal study. A unique feature of IRT based DataK-RA scores is that they are expressed in a metric in which the unit of measurement is independent of the administered items. Hence these norm scores pertain to all applications of the DataK-RA item bank (e.g. computer adaptive tests, tailored short forms). According to the COTAN quality criteria, sample sizes for the overall percentile scores were 'good' (n ≥ 400) and 'adequate' (300 ≥ n &lt; 400) for all stratified percentiles, except patients with high educational level. <h3>Disclosure of Interests:</h3> Lisanne Renskers: None declared, Martijn Oude Voshaar: None declared, Marieke J de Jonge: None declared, Sanne AA Rongen-van Dartel: None declared, Anita M P Huis: None declared, Mart van de Laar Grant/research support from: AbbVie, Eli Lilly, Janssen-Cilag, Merck Inc, Pfizer Inc, Sanofi Genzyme, Speakers bureau: Eli Lilly, Pfizer Inc, Piet L.C.M. van Riel: None declared