Table 1

Summary of the common internal quality control (IQC) rules used for a two-level IQC system12

IQC ruleInterpretation12
Warning rule
 12s When one control exceeds 2 s limits, inspect control data further using additional rules
Within run
 13s Reject run when one control result exceeds 3 s limits
 22s*Reject run when both control results exceed the same+2 s or −2 s limits
 R4s Reject run when one control result exceeds+2 s and the other exceeds −2 s within the same run
Across runs
 22s*Reject when the previous result on the same IQC material exceeds the same+2 s or -2 s limit.
 41s*Reject when last four consecutive control measurements (across different control material or on same control material) exceed the same+1 s or −1 s limit.
 10x Reject when last 10 consecutive control measurements (across control materials or on same control material) fall on the same side of the mean
  • *Note that these rules are used both across and within run.