Determine Quality Requirements for the Test

How good does a test need to be? Answering this question will help determine the total allowable error (TE_a); the amount of error a test has and is still considered "in control." The laboratory can use several models to determine quality requirements:

1. Medical usefulness requirements based on the effect of analytical performance on clinical decisions such as:
   • Biological variation information.
   • Clinicians' opinions.
2. Published professional recommendations from:
   • National and international expert bodies and agencies.
   • Expert local groups or individuals.
3. Performance goals set by:
   • Regulatory bodies and agencies.
   • Organizers of External Quality Assessment (EQA) schemes.
4. Goals based on the current state of the art, which include:
   • Interlaboratory comparison programs such as the Unity™ Interlaboratory Program.
   • EQA or proficiency testing schemes.
   • Current published information on methodology.

The preceding hierarchy is based on the consensus agreement published in the Scandinavian Journal of Clinical and Laboratory Investigation 1999; 59: 585.

Note: When available and appropriate, models higher in the list are preferred to those lower in the list.

Based on requirements needed to maintain accreditation, proficiency testing requirements define the minimum standards for performance. While proficiency testing may be appropriate for some tests, medical usefulness requirements are usually more stringent and may be preferred.