Letting Go of the Rules of Three… and How Not to Let the MCHC Rule Your Life

12:00 PM to 1:00PM (Americas) Central Time (US & Canada)

Jeri Walters, SH(ASCP), Technical Supervisor Esoteric Testing, WI Core Lab, ACL Laboratories, West Allis, WI

The rules of 3 have been a staple in hematology for decades. This presentation will review the history of the rules of 3 and discuss why they were introduced into lab hematology – and why they need to go away. We will examine how modern sheath flow-based hematology analyzers have made the rules of 3 obsolete and why the RBC indices are much better indicators of problem samples. Learn what may cause abnormal and improbable indices and what to do about it.


  • Discuss the history of the rules of 3 and their original purpose in hematology testing
  • Explain the importance of the RBC indices and how they are better indicators of problem samples
  • Apply your knowledge of what can cause ‘spurious’ indices and identify alternate methods to resolve the problem

This session provides 1 contact hour through P.A.C.E.® and the state of Florida.

Sysmex America is approved as a provider of continuing education programs in the clinical laboratory sciences by the ASCLS P.A.C.E.® program.

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