Molecular Quality Controls

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Use Ct value to monitor assay performance

Statistics-based quality control is the best way to monitor assay performance. In real-time PCR a positive reaction is identified by buildup of a fluorescent signal. The cycle threshold (Ct) is defined as the number of cycles required for the reaction’s fluorescence to exceed background levels and cross the threshold. Ct levels are inversely proportional to the concentration of the specific nucleic acid in the sample that is being measured. A lower Ct value indicates a greater concentration of the measured analyte in the sample. A shift in the Ct value may signal a performance issue before it affects patient results.

Even though many infectious disease NAT methods are qualitative, a Ct value or other semi-quantitative measurement may be provided for each detected gene. These values can be reported in the Unity Interlaboratory Program for peer group comparison.

The Ct values can also be used with other Unity QC tools like Levey-Jennings charts and Westgard rules to monitor any trends or shifts over time.

The upward trending of the control’s Ct value may indicate a decreasing PCR ef ciency (not actual data) The upward trending of the control’s Ct value may indicate a decreasing PCR efficiency (not actual data).

Unity Interlaboratory Program

Participation in a high quality Interlaboratory program is as important as ever for laboratories to help ensure the reliability and precision of testing systems.

Without a high-quality Interlaboratory program, your laboratory may not be aware of gradual or sudden changes in your test system that are often caused by events such as reagent or calibrator reformulations, standardization changes, or instrument software changes. An Interlaboratory program can offer awareness of shifts and trends and help verify the reliability of laboratory testing.

No program in the world is more powerful and effective at providing information and improving laboratory analytical performance than Bio-Rad's Unity Interlaboratory Program.

Worldwide Peer Groups

  • Compare your quality control results to other laboratories worldwide at any time.
  • Utilize peer comparison to troubleshooting problems with test system performance.
  • Access data generated from more than 46,000 instruments in 92 countries to successfully manage and interpret your quality control results.

Additional Resources