Difference Between Out of Specification and Out of Trend

1. OOS (out of specification) is the comparison of one result versus predetermined specification criteria while OOT (Out of Trend) is the comparison of many historical data values versus time.

2. OOS investigations focus on determining the truth about that one value while OOT investigations focus on understanding non-random changes.
Example:

The specification limit for assay is: 95.0-105.0 % w/w of label claim

Case-1: For a particular batch, the result obtained 94.2 % w/w -This result is out of the specification limit. This is called OOS.

Case-2: The result obtained 95.8 % w/w. Although the results are well within the specifications, we should compare the result with the previous batches trend. If we found the average value of the trend as 99.0 % w/w then this batch result (95.8 % w/w) is called out of trend.

Also see:

• SOP for Handling of Out of Limit Results in Environmental Monitoring and Water Analysis
• SOP for Handling of Out of Specification Results in Microbiological Testing
• SOP for Microbial Limit Test of Raw Material and Finished Product