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Preanalytical Variation in Clinical Laboratory Testing

Clinical Chemistry

  1. Namrata Setia,
  2. James H. Nichols

Published Online: 15 DEC 2009

DOI: 10.1002/9780470027318.a9115

Encyclopedia of Analytical Chemistry

Encyclopedia of Analytical Chemistry

How to Cite

Setia, N. and Nichols, J. H. 2009. Preanalytical Variation in Clinical Laboratory Testing. Encyclopedia of Analytical Chemistry. .

Author Information

  1. Tufts University School of Medicine, Baystate Medical Center, Department of Pathology, Springfield, Massachusetts, USA

Publication History

  1. Published Online: 15 DEC 2009


Laboratory testing can be divided into preanalytic, analytic, and postanalytic phases. Medical errors are most frequent in the preanalytic phase of testing. Preanalytic variables can affect test results, leading to misinterpretation and inappropriate patient care. Physicians should be educated on the potential for preanalytic variation and to question test results for potential preanalytic effects whenever the result does not match the clinical symptoms. Preanalytic variables can be controllable, such as diet, exercise, and drug intake, or they can be noncontrollable, inherent to the patient's age, sex, race, or disease state.

Preanalytic variables can occur at many steps in the testing process. Physicians and clinical staff can misinterpret test names and order the wrong test or methodology. Biological factors, such as fasting, may require the patient to prepare before specimen collection or a sample may need to be collected at an appropriate time for therapeutic drug monitoring or hormone interpretation. Several sources of preanalytic variation have been related to specimen collection, including patient identification, specimen additives, order of draw, sample mixing, specimen volume, phlebotomy technique, needle size, and use of vascular access devices. Delays in transportation and inappropriate storage of samples after analysis can also adversely affect test results.

Some preanalytic variables can be detected, such as hemolysis, lipemia, and icterus by visual inspection of each specimen, but other sources of variation are not readily detectable. Newer analyzers can spectrophotometrically analyze each specimen for interferences due to hemolysis, lipemia, and icterus, automating the ability to comment and qualify a test result on the basis of the level of interferent. Education and awareness, however, remain an important means of managing preanalytic effects as a source of laboratory result variation.


  • preanalytic variables;
  • order entry;
  • specimen collection;
  • error detection;
  • laboratory testing