Demystifying Linearity Testing in Today’s Clinical Laboratory

 Demystifying Linearity Testing in Today’s Clinical Laboratory

by Robert J. Janetschek

CLIA’88 and subsequent revisions now mandate that all clinical laboratories perform calibration verification procedures to confirm the continued accuracy of their testing systems. This requirement applies to every laboratory and testing site in the U.S., regardless of the testing volumes it handles. To meet CLIA requirements, testing sites must conduct defined studies to prove that their clinical testing equipment and subsequent test results are consistently accurate.  A major component of these studies is the need for calibration verification testing, which needs to be performed, at a minimum, once every six months.

Although the CLIA mandates have been in effect for quite some time, the unfortunate fact is that many experienced administrators and lab personnel still express confusion when it comes to linearity, reportable range and analytical measurement range (AMR). Frankly, it is not too surprising this has occurred; CLIA uses one set of terms and definitions, while other industry agencies and regulatory bodies use different ones. And it is important to understand the difference between these three criteria, as it impacts laboratory inspections and compliance. In fact, one of the top five reasons for a laboratory to be served with a noncompliance citation has been reported as “not performing calibration verification according to the manufacturer's instructions including: the number, type and concentration of materials to be used; use of materials at low, medium and high values within the reportable range as determined by the laboratory; acceptable limits for calibration verification, once every 6 months or more often, if required by laboratory procedures.”

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