The most common use of AAPs is for non-regulated analytes and for regulated analytes for which commercially approved PT is not available. The laboratory may select one or more procedural approaches to alternative assessment to verify the accuracy of test results for each analyte, minimally twice a year.
An additional scenario that may employ AAPs is when commercial PT evaluation does not provide adequate assessment information. When PT is scored as "Ungraded" or "Lack of Consensus," the data obtained by the PT provider did not yield sufficient data to provide validation of accuracy. In these cases, the event/analyte is scored as 100% but may not be reflective of the actual score.
Options for alternative assessment that employ patient samples have some advantages over commercially prepared materials. These advantages include (CLSI QMS 24):
- Avoiding matrix effects of the samples provided for analysis
- Independence from the routine QC system
- Evaluation of pre-analytic factors
Options for AAPs include a variety of assessment activities including (but not limited to):
- Ungraded or educational test challenges
- Split sample analysis with comparison to an established in-house method. In house method options include the use of:
- Assayed material -- such as calibration material from a lot number not currently being employed by the laboratory for verification of testing accuracy
- Regional pools -- pooled samples from multiple sources with repeated analyses and data analysis for comparison
- Audit patient samples over time
- Clinical validation by chart review of patient clinical results
At the inception of a laboratory's quality assessment (QA) and PT plans, the laboratory administration will determine the measurands and test methods for which AAPs will be applied.
It is the responsibility of the laboratory director to define AAPs and criteria for successful performance (eg, within 10% of a reference method). The process and evaluation must be aligned with good clinical laboratory practices.
All documentation for AAPs is properly noted and retained for a minimum of two years or for the period of time required by regulatory agencies, whichever is greater.
