Action limit outlier test: a novel approach for the identification of outliers in bioassay dose-response curves.

Aim/Materials & methods: Guidelines like United States Pharmacopeia 1032 [1] and pharm.Eur. [2] acknowledge that cell-based bioassays are complex methods and thus prone to outliers. However, investigations into root causes of outliers are often inconclusive. We have established a procedure (including quality control and documentation) implemented in a freely available software application which includes not only the experience of the analyst but also information of historical data. Results: This action limit outlier test is unique to our knowledge. Action limit outlier test allows the determination of outliers efficiently which lead to a significant reduction of false positives in comparison with the traditional outlier test ROUT [3] or Rosner [4] alone as shown by our simulated data (58 and 44% reduction of false positives for ROUT and Rosner, respectively).