Calculating the Reportable Result from Retest Data - Pharmaceutical Technology

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Calculating the Reportable Result from Retest Data
Two methods to evaluate retest data following out-of-specification results.

Pharmaceutical Technology
Volume 37, Issue 2


Two established approaches for evaluating retest data following an OOS result have been described together with a method for generating a reportable result. These two approaches are not the only ones and companies are free to select and defend their own statistical approaches. Whichever approach is selected, the choice must be documented, justified, and described in an SOP.


1. United States vs. Barr Laboratories, Inc. Civil Action No. 92-1744, US District Court for the District of New Jersey: 812 F. Supp. 458. 1993 US Dist. Lexis 1932; Feb. 4, 1993, as amended Mar. 30, 1993.

2. FDA, Investigating Out-of-Specification (OOS) Test Results for Pharmaceutical Production (Rockville, MD, Oct. 2006).

3. European Compliance Academy (ECA) Analytical Quality Control Working Group website,, accessed Jan. 7, 2012.

4. C. Burgess and B. Renger, ECA Standard Operating Procedure 01, Laboratory Data Management; Out of Specification (OOS) Results, Version 2, Aug. 2012.

5. L.D. Torbeck, Pharm. Tech. 35 (12), 28, 54 (2011).

6. M. Thompson and P.J. Lowthian, Notes on Statistics and Data Quality for Analytical Chemists, Section 7.6; Huber's H15 method, Imperial College Press, 2011, ISBN-10 184816-617 & references therein.

7. S.L.R. Ellison, V.J. Barwick, and T.J. Duguid Farrant, Practical Statistics for the Analytical Scientist, Section 5.3; Robust Statistics, Royal Society of Chemistry, 2009, ISBN 978-0-85404-131-2.

Chris Burgess, PhD,is an analytical scientist at Burgess Analytical Consultancy Limited, 'Rose Rae,' The Lendings, Startforth, Barnard Castle, Co Durham, DL12 9AB, UK; Tel: +44 1833 637 446;


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