Per Clin Lab Navigator, approximately 66% (13 points) of the values should fall between +/- 1 SD ranges and be evenly distributed on either side of mean. Ninety five percent of values should lie between +/- 2 SD ranges and 99% between the +/- 3 SD limits. In general, +/- 2 SD limits are considered to be warning limits. Values falling between 2 SD and 3 SD indicate the analytic run should be reviewed. The +/-3 SD limits are rejection limits, though not always, due to small SD’s by newer instruments. Usually, when a QC value falls outside of these limits the analysis should stop, patient results should be held, and the test system investigated. First make an effort to troubleshoot and rule out instrument, reagent and/or calibration issue.
If troubleshooting is unsuccessful, call your instrument manufacturer and/or Bio-Rad. You can reach Bio-Rad Technical Support at 1-800-854-6737 in US or by email at qsd. firstname.lastname@example.org.