Table 2

Summary of recommendations provided by the 2010 convocation of experts on laboratory quality for the use of six sigma to initiate internal quality control (IQC) design.16

Sigma scorePerformanceIQC design16
 >6σExcellentOnce per day
One level per day (alternating levels)
13.5s rule
4σ–6σSuited to purposeOnce per day
Two levels per day
Single IQC rule
3σ–4σPoor performersTwice per day
Two levels of IQC per day
Multirule system
<3σProblematicThree times a day
Three levels
Consider testing in duplicate
Maximum IQC rules