Preoperative quadriceps strength as a predictor of return to sports after anterior cruciate ligament reconstruction in competitive athletes

We review the principles and practical application of receiver-operating characteristic (ROC) analysis for diagnostic tests. ROC analysis can be used for diagnostic tests with outcomes measured on ordinal, interval or ratio scales. The dependence of the diagnostic sensitivity and specificity on the selected cut-off value must be considered for a full test evaluation and for test comparison. All possible combinations of sensitivity and specificity that can be achieved by changing the test's cut-off value can be summarised using a single parameter; the area under the ROC curve. The ROC technique can also be used to optimise cut-off values with regard to a given prevalence in the target population and cost ratio of false-positive and false-negative results. However, plots of optimisation parameters against the selected cut-off value provide a more-direct method for cut-off selection. Candidates for such optimisation parameters are linear combinations of sensitivity and specificity (with weights selected to reflect the decision-making situation), odds ratio, chance-corrected measures of association (e. g. kappa) and likelihood ratios. We discuss some recent developments in ROC analysis, including meta-analysis of diagnostic tests, correlated ROC curves (paired-sample design) and chance- and prevalence-corrected ROC curves.

Many different methods of evaluating disability after knee ligament injury exist. Most of them differ in design. Some are based on only patients' symptoms. Other include patients' symptoms, activity grading, performance in a test, and clinical findings. The rating in these evaluating systems can be either numerical, as in a score, or binary, with yes/no answers. Comparison between a symptom-related score and a score of more complex design showed that the symptom-related score gave a more differentiated picture of the disability. It was also shown that the binary rating system gave less detailed information than a score and that differences in a binary rating can depend on at what level the symptoms are regarded as "significant." A new activity grading scale, where work and sport activities were graded numerically, was constructed as complement to the functional score. When evaluating knee ligament injuries, stability testing, functional knee score, performance test, and activity grading are all important. However, the relative importance varies during the course of treatment, and therefore they should not all be included in one and the same score.