One form of an AAP is split sample testing. Split sample testing may be incorporated into the PT plan to validate proficiency for non-regulated analytes and specific applications deemed appropriate by laboratory management. However, it cannot be used as a replacement for PT for regulated analytes.
Split sample comparison is performed by splitting a single sample into two aliquots. One aliquot is tested using the primary test method, while the second aliquot is tested using the same or an alternate test method at another acceptable laboratory.
The laboratory will complete split sample AAP for any of the following purposes:
- Verify the accuracy of non-regulated analytes for which commercial PT is unavailable or utilized.
- Compare a test or analyte to an alternate comparison method. The comparison method must be performed in a CLIA-certified facility of the same or higher complexity level as the facility possessing the primary testing method.
- The alternate comparison method may be an internal test method for the same test or analyte performed in-house by different methods and for which duplicate PT is not performed. Each facility that tests an analyte by multiple test methods must verify the accuracy of all test methods. Still, the regulatory restrictions prohibit ordering various kits for the duplicate testing method before the due date for the primary test method. Alternatively, a separate reference laboratory or another CLIA-certified laboratory with an appropriate comparison method for the same analyte(s)may be used for this purpose.
- Additionally, split sample analysis may be utilized to determine the cause of inaccurate test results or test system problems.
- Split samples may also be incorporated into validating a new analytic method. Split sample analysis employed in the validation process is not part of PT and is known as correlation studies.
