Warning Rules

1. The control value exceeds the mean by 2 s.d. (p<.005)
2. Two consecutive values exceed the target value on the same side of the mean by 2 s.d. This may indicate the presence of systematic errors.
3. Four consecutive control values exceed the same limit. This again indicates the possible presence of systematic errors and may indicate the need to perform instrument maintenance or equipment calibration.

Mandatory rules

1. The control value exceeds the target value by 3.s.d. (p<0.01:99.7% of values should lie within 3 s.d.) This indicates that the assay run is out of control
2. Where the IQC sample is tested in duplicate, the difference in SD between the duplicates should not exceed 4 SD
3. 10 consecutive values are on the same side of the mean or target value. This detects systematic errors. This may happen when a new test batch or introduced or changes in the calibration of equipment.