The key difference between OOS and OOT lies in what is being evaluated: OOS (Out Of Specification) refers to results that don't meet pre-defined acceptance criteria, while OOT (Out Of Trend) refers to results that deviate from an established pattern or history of previous results.
Here's a more detailed breakdown:
OOS (Out Of Specification)
- OOS results indicate a failure to meet a specific requirement or limit defined in a test's acceptance criteria.
- It means the product or material does not conform to its intended quality standards.
- According to the reference provided, "The Quality Control (QC) declares the result as OOS if it doesn't comply or agree with the given test result criteria."
- Example: A drug product assay result is 95%, but the specification requires it to be between 98% and 102%. This is an OOS result.
OOT (Out Of Trend)
- OOT results indicate a significant departure from a historical data trend.
- The result may still be within specification but is unexpected based on past performance.
- According to the reference provided, "Out of trend (OOT) is defined as a result that falls outside the trend. QC compares the result of the current test with a set of previous results to check with the on-going trend."
- Example: The typical moisture content for a raw material has been consistently between 2% and 3% for the past year. A recent test result shows a moisture content of 4%, even though the specification allows up to 5%. This would be an OOT result, even if it is in specification.
Summary Table
| Feature | OOS (Out Of Specification) | OOT (Out Of Trend) |
|---|---|---|
| Definition | Fails to meet pre-defined acceptance criteria. | Deviates significantly from established historical trends. |
| Compliance | Doesn't comply with defined specifications. | May or may not be within specification limits. |
| Evaluation Basis | Compared against a fixed acceptance range. | Compared against historical data patterns. |
| Implication | Product does not meet quality standards directly. | Indicates a potential change in the process. |
| Action Required | Immediate investigation and corrective action are necessary. | Investigation to determine the cause of the trend change is needed. |
In essence, OOS is an immediate red flag concerning product quality, whereas OOT signals a potential problem with the manufacturing process that warrants investigation, even if the product still meets defined specifications.
