ECA AQCG OOS Survey: A First Short Summary

How does your organisation handle Out-of-Specification (OOS) results in practice? To capture current approaches across the industry, the ECA Analytical Quality Control Group (AQCG) invited professionals to share their experience and contribute to the ongoing update of the AQCG OOS guidance.

The survey explored how organisations structure OOS procedures, distinguish between OOS/OOT/invalid results, apply second-person review, use hypothesis testing, manage re-analysis and retesting, integrate manufacturing review, and implement CAPA.

Examples of survey questions included:

• Do you clearly define what constitutes an OOS test result?
• Do you make a distinction between OOS, OOT (atypical, aberrant), and invalid results?
• Do you apply a replication strategy and define the mean as the reportable result?
• Do you describe timelines for each investigation phase (e.g., Phase I, IA, IB, Phase II and Phase III within X days)?  
• At which stage(s) do you perform a second-person review?
• Do you use a step-by-step checklist during Phase I?
• Do you describe retesting procedure (e.g. sample size, outlier test and evaluation) in your analytical procedure SOP?

The survey closed in April. Based on 169 complete responses, the results suggest that many of the fundamentals are highly standardised: numerous organisations report clear internal definitions and distinctions (e.g., OOS vs. OOT/atypical vs. invalid results), supported by structured Phase I workflows with checklists and formal documentation. Second-person review steps also appear to be widely embedded.

At the same time, greater variability emerges in how organisations approach repeats/replicates, averaging, and the question of what ultimately constitutes the reportable result. Similarly, when asked whether organisations have a structured approach to hypothesis testing (e.g., using fishbone analysis or comparable tools), responses indicate a spectrum—from formalised, tool-supported workflows to more pragmatic, case-by-case assessments.

The AQCG is now completing the detailed evaluation of the survey results. The findings will feed into the ongoing update of the AQCG OOS guidance, and a consolidated summary will be shared once available.