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Further Simplification of the Simple Erosion Narrowing Score With Item Response Theory Methodology
Author(s) -
Oude Voshaar Martijn A. H.,
Schenk Olga,
ten Klooster Peter M.,
Vonkeman Harald E.,
Bernelot Moens Hein J.,
Boers Maarten,
van de Laar Mart A. F. J.
Publication year - 2016
Publication title -
arthritis care and research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.032
H-Index - 163
eISSN - 2151-4658
pISSN - 2151-464X
DOI - 10.1002/acr.22793
Subject(s) - medicine , statistics , item response theory , orthodontics , psychometrics , mathematics , clinical psychology
Objective To further simplify the simple erosion narrowing score (SENS) by removing scored areas that contribute the least to its measurement precision according to analysis based on item response theory (IRT) and to compare the measurement performance of the simplified version to the original. Methods Baseline and 18‐month data of the Combinatietherapie Bij Reumatoide Artritis (COBRA) trial were modeled using longitudinal IRT methodology. Measurement precision was evaluated across different levels of structural damage. SENS was further simplified by omitting the least reliably scored areas. Discriminant validity of SENS and its simplification were studied by comparing their ability to differentiate between the COBRA and sulfasalazine arms. Responsiveness was studied by comparing standardized change scores between versions. Results SENS data showed good fit to the IRT model. Carpal and feet joints contributed the least statistical information to both erosion and joint space narrowing scores. Omitting the joints of the foot reduced measurement precision for the erosion score in cases with below‐average levels of structural damage (relative efficiency compared with the original version ranged 35–59%). Omitting the carpal joints had minimal effect on precision (relative efficiency range 77–88%). Responsiveness of a simplified SENS without carpal joints closely approximated the original version (i.e., all Δ standardized change scores were ≤0.06). Discriminant validity was also similar between versions for both the erosion score (relative efficiency = 97%) and the SENS total score (relative efficiency = 84%). Conclusion Our results show that the carpal joints may be omitted from the SENS without notable repercussion for its measurement performance.