The pharmaceutical industry still lacks having a proper guideline for the identification of present OOT results among ongoing
stability data. As a result, many pharmaceutical companies are not harmonized in the way they conduct this type of analysis.
In this study, three methods for identification of OOT results in ongoing stability data were proposed: the regression-control-chart
method, the by-time-point method, and the slope-control-chart method. To obtain more accurate identification of existing OOT
results, simultaneous use of all three methods is advised, which will result in getting a visual image of the results of the
analyzed batches. The use of the z-score method for defining the limits for the OOT results is preferred. Lastly, the study
highlighted the necessity of issuing a regulatory confirmed guideline for identification of OOT results within ongoing stability
Adrijana Torbovska* is an analyst in the Quality Control Department of ReplekPharm, Kozle 188, 1000 Skopje, Macedonia, firstname.lastname@example.org
Suzana Trajkovic-Jolevska, PhD, is a professor in the Drug Quality Control Department, Faculty of Pharmacy, Ss Cyril and Methodius University, Skopje, Macedonia.
* To whom all correspondence should be addressed.
1. MHRA, Guidance for Out Of Secification Investigation, online presentation, (2010),
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2. FDA, Guidance for Industry: Investigating Out-Of-Specification (OOS) Test Results for Pharmaceutical Production (Rockville, MD, 2006).
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