SAT0727-HPR Criterion validity and reliability of a submaximal treadmill test in juvenile idiopathic arthritis patients

Background For both research purposes and daily clinical practice, a feasible exercise test with acceptable measurement properties is needed to measure exercise capacity in juvenile idiopathic arthritis (JIA) patients. Objectives To evaluate the criterion-validity, test-retest reliability and inter-rater reliability of an eight-minute submaximal treadmill test, which can be used to estimate VO 2peak 1 , in JIA patients. Methods 59 patients with oligo- (n=30) and polyarticular (n=29) JIA (mean age (SD) 13.6 (2.2), 50 girls) participated in this study. They performed a maximal treadmill test until exhaustion to measure the VO 2peak directly and the eight-minute submaximal treadmill test to estimate the VO 2peak . A standardised formula was used to estimate the VO 2peak 1 . To evaluate the reliability, 37 patients also performed the submaximal treadmill test twice on the same day 1–4 weeks after the initial test. Paired t-tests were used to test potential differences between the tests. Criterion validity and reliability were evaluated with two ways mixed interclass correlation coefficient agreement (ICC). Limits of agreement (LoA) (Bland and Altman method), standard error of measurement (SEM agreement ) and smallest detectable change (SDC 95 ) were calculated to evaluate the measurement error of the submaximal treadmill test. Results No significant difference was found between the observed and estimated VO 2peak (mL·kg -1 ·min -1 ), 44.8 (8.8) vs 43.2 (10.3) respectively, p=0.18. The single ICC (95% CI) value at individual level between the estimated and measured VO2peak was moderate; ICC 0.55 (0.34–0.70) while the ICC at group level was good; 0.71 (0.51–0.82). The measurement errors were large (SEM 6.5 and SDC 95 18.0). The single ICC value for test-retest reliability and interrater reliability were good to excellent, 0.84 (0.71–0.91) and 0.92 (0.83–0.96), respectively. The ICC value at group level for test-retest reliability and interrater reliability were excellent, 0.91 (0.83–0.96) and 0.96 (0.91–0.98), respectively. There were no significant differences between estimated VO 2peak (mL·kg -1 ·min -1 ) when comparing the results from the three performed submaximal treadmill tests. The measurement errors were moderate/large for both test-retest reliability and interrater reliability (table 1). The Bland Altman plots showed no systematic differences, but confirmed the large variability for both the validity and reliability (figure 1). Conclusions The submaximal treadmill test is valid for use in JIA patients on group level, but showed only moderate validity on an individual level. The test- retest and intra-rater reliability is good to excellent; however, the measurement errors are large. Our findings indicate that the submaximal treadmill test is not optimal for use in daily clinical practice to estimate VO 2peak in individual patients and it is important to be aware of the large measurement errors. Reference [1] Ebbeling, et al. 1991. Disclosure of Interest None declared