The trigonometric responder approach: a new method for detecting responders to pharmacological or experimental challenges.

The paper presents a newly developed response measure that is particularly suitable for the evaluation of pharmacokinetic data. This method is based on trigonometric considerations, defining a hormone response as the difference between the angle of the slope of the curve before and after drug intake. In addition, the size of this difference is compared to the difference obtained in placebo conditions. In this way, the trigonometric response measure overcomes one of the most problematic shortcomings of the 'area under the curve' (AUC) approach, the problem of the initial value. We will present the mathematical background of the trigonometric method and demonstrate its usefulness by evaluating empirical data (a pharmacological challenge test using the dopamine agonist lisuride) and comparing it to classical AUC measures. This has been achieved by contrasting both approaches with responder definitions according to binary time series analysis and the peak value of the curve.