1. OOS (out of specification) is the
comparison of one result versus a predetermined specification criterion 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
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 of 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.
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