OBJECTIVE: To examine the construct validity of the 28-tender joint count (TJC-28) using item response theory (IRT)-based methods. METHODS: A total of 457 patients with early stage rheumatoid arthritis (RA) were included. Internal construct validity of the TJC-28 was evaluated by determining whether the TJC-28 fit a 2-measure logistic IRT model. As well, we tested whether the discrimination and difficulty parameters of the joints properly reflected the known left-right symmetry of joint involvement. External validity was evaluated by correlations with other established measures of disease activity, including pain, disability, general health, erythrocyte sedimentation rate (ESR), and the 28-swollen joint count. RESULTS: The TJC-28 showed a good fit with the 2-parameter logistic model, with no relevant differential item functioning across sex, age, and time and with excellent reliability. The 28 joints covered a reasonable range of disease activity, even though they were mainly targeted at patients with moderate or high disease activity levels. The joint parameters reflected the left-right symmetry of joint involvement for all pairs of joints except one. All disease activity measures, except ESR, were significantly correlated with the TJC-28. Most correlations were of the expected magnitude. CONCLUSION: The TJC-28 showed good internal and acceptable external construct validity for patients with early-stage RA. The IRT analyses did point to some potential limitations of the instrument, a major problem being its limited measurement range. Future research should examine whether instrument modifications might lead to a more robust assessment of disease activity in patients with RA.
OBJECTIVE: To examine the construct validity of the 28-tender joint count (TJC-28) using item response theory (IRT)-based methods. METHODS: A total of 457 patients with early stage rheumatoid arthritis (RA) were included. Internal construct validity of the TJC-28 was evaluated by determining whether the TJC-28 fit a 2-measure logistic IRT model. As well, we tested whether the discrimination and difficulty parameters of the joints properly reflected the known left-right symmetry of joint involvement. External validity was evaluated by correlations with other established measures of disease activity, including pain, disability, general health, erythrocyte sedimentation rate (ESR), and the 28-swollen joint count. RESULTS: The TJC-28 showed a good fit with the 2-parameter logistic model, with no relevant differential item functioning across sex, age, and time and with excellent reliability. The 28 joints covered a reasonable range of disease activity, even though they were mainly targeted at patients with moderate or high disease activity levels. The joint parameters reflected the left-right symmetry of joint involvement for all pairs of joints except one. All disease activity measures, except ESR, were significantly correlated with the TJC-28. Most correlations were of the expected magnitude. CONCLUSION: The TJC-28 showed good internal and acceptable external construct validity for patients with early-stage RA. The IRT analyses did point to some potential limitations of the instrument, a major problem being its limited measurement range. Future research should examine whether instrument modifications might lead to a more robust assessment of disease activity in patients with RA.
Authors: Liseth Siemons; Peter M ten Klooster; Harald E Vonkeman; Mart A F J van de Laar; Cees A W Glas Journal: PLoS One Date: 2014-06-23 Impact factor: 3.240
Authors: Thomas Dörner; Yoshiya Tanaka; Ernst R Dow; Alisa E Koch; Maria Silk; Jorge A Ross Terres; Jonathan T Sims; Zhe Sun; Inmaculada de la Torre; Michelle Petri Journal: Ann Rheum Dis Date: 2022-05-24 Impact factor: 27.973
Authors: Liseth Siemons; Peter M Ten Klooster; Erik Taal; Cees Aw Glas; Mart Afj Van de Laar Journal: BMC Musculoskelet Disord Date: 2012-10-31 Impact factor: 2.362