External Quality Assessment

How to Subscribe
MLS & MLT Comprehensive CE Package
Includes 180 CE courses, most popular
$109Add to cart
Pick Your Courses
Up to 8 CE hours
$55Add to cart
Individual course$25Add to cart
Need multiple seats for your university or lab? Get a quote
The page below is a sample from the LabCE course Introduction to Quality Control. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

Learn more about Introduction to Quality Control (online CE course)
External Quality Assessment

External quality assessment or proficiency testing (PT) is performed to ensure the reliability of test results by comparing results to other laboratories that use the same method system and/or to an assigned value.
The CLIA standards for handling proficiency testing specimens are as follows:
  • PT samples must be tested with the laboratory's regular patient load.
  • PT samples must be tested the same number of times that patients' samples are tested routinely.
  • Laboratories participating in PT programs must not engage in an interlaboratory comparison of PT sample results.
  • Laboratories may not send PT samples to another laboratory for analysis.
  • Laboratories must document all steps of processing for PT samples.
  • PT is required for only the primary method used for testing analytes in patients' samples during the period covered by the PT event.
In return for their participation, the laboratory will receive the following information:
  • Results for each analyte sample;
  • Mean result for each analyte;
  • Standard deviation of results by the comparative method;
  • Number of laboratories using the same method;
  • Standard deviation index (SDI); and
  • Lower and upper limits of acceptability of results.
PT results that are between the lower and upper limits of acceptability are considered satisfactory.
External quality control serves several purposes, including:
  • Evaluating the internal quality control program;
  • Detecting errors in a lab's methods, including technical errors; and
  • Providing a comparison of testing methods, which is useful in selecting new methods.