This study evaluated inter- and intra-observer reliability and discriminative validity of three movement control tests: 1) standing knee-lift test; 2) static lunge test; and 3) dynamic lunge test. Thirty-eight subjects, 21 with low-back pain and 17 healthy, were video-recorded while performing the tests. Four physical therapists scored the tests according to a standardized protocol and calculated a composite score for each test based on the number of incorrect test components. Inter-observer reliability for the composite scores ranged between 0.68 and 0.80 (ICC 2,k) and intra-observer reliability between 0.54 and0.82 (ICC 2,1). The separate test components ranged between 0.32 and 0.91 (κ) for inter-observer reliability and 0.42 and1.00 for intra-observer reliability. Test components showing the highest values were: back extension; arm lowering; and shoulders moving backwards. Components hip hitch, trunk lateral flexion, knee not lifted straight up and hips moving backwards did not reach accepted thresholds. Discriminative validity ranged between 0.47 and 0.56 (AUC). As our results showed an overall good agreement for the composite, scores and for the majority of the included test components the tests can be considered reliable enough. As the tests' discriminative ability was close to "none", they should, however, not be used for diagnostic purposes but should be further evaluated toward predicted validity.

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Purpose There is a wide selection of instruments and questionnaires available, but many are time consuming in their administration, for patients, practitioners and researchers alike. The Core Outcome Measures Index (COMI) is a short, selfadministrated, multidimensional instrument translated into several languages that covers five domains recommended in the assessment of outcome in patients with low-back pain. The purpose of this study was to cross-culturally adapt the COMI from English to Swedish and to test the face and construct validity and reproducibility of its results in patients with low-back pain. Methods Participants (n = 102) were included from primary and secondary care. The participants reported moderate pain and disability levels. All participants filled in the COMI, the Oswestry Disability Index and the EQ5D at baseline. Forty-nine filled in the COMI again after 7 days for the reproducibility part of the study. Results The instrument was successfully forward and back-translated. In the validation process, there were low floor/ceiling effects, with the exception of the symptom-specific well-being (floor) and work disability (ceiling) items. The specific COMI domains and whole score correlated significantly with the chosen reference scale scores to the hypothesised extent (Rho 0.30-0.60 and > 0.60 respectively). COMI reached ICC 0.63 (95% CI 0.42-0.77) in the reproducibility test and the separate items, ICC 0.41-0.78. Conclusions The Swedish COMI shows acceptable psychometric properties and is thus suitable to use as a short instrument for measuring important domains in patients with low-back pain. A future study should investigate the instrument's sensitivity to measure change after treatment.