QC results are used to validate whether an instrument is performing within predetermined specifications so that the laboratory can infer that the patient results released are accurate.
Labs are encouraged to perform two levels of internal QC as a part of their daily quality checking. NABL and US CLIA regulations recommend each laboratory to establish its own lab mean, rather than going by the range provided by the QC manufacturer.
Values and limits found on assay sheets often describe the performance observed by a specific method in different laboratories, and may not be applicable to all laboratory conditions and instruments.
The ranges are likely to be too wide/inaccurate for an individual method in the laboratory. If the control limits are too wide, the lab won’t be able to detect problems in its own laboratory.