Michael M. Fry, DVM, MS, DACVP
Department of Biomedical and Diagnostic Sciences, College of Veterinary Medicine University of Tennessee Knoxville, TN, USA
Laboratory quality management (QM) refers to the principles, systems, and tasks required to ensure quality test results.
Human clinical laboratories in the USA are federally regulated. Veterinary clinical laboratories are not, so the commitment to quality laboratory testing must come from within the profession.
QM and Organized Veterinary Medicine
These are the opening lines from a 2004 Special Report published in the Journal of the American Veterinary Medical Association:
"Valid and correctly applied test results are critical to a veterinary practitioner's credibility, protection from liability, client livelihoods, public health, trade, and the health of animals. Practitioners should know how to ensure the quality of testing that is performed in their practice and be aware of the questions to ask of outside laboratory services."
Few veterinarians would dispute that valid test results are critically important. However, it is likely that a much higher proportion of veterinarians would admit to a tenuous grasp of how to ensure the quality of test results generated in their own practice or by an outside laboratory.
Veterinary clinical pathologists are making a concerted effort to advance laboratory quality management within the profession. Establishing and promoting laboratory standards is an organizational priority of the American Society for Veterinary Clinical Pathology.
Veterinary technicians play a key role in laboratory quality management. A related recent development, by the National Association of Veterinary Technicians of America (NAVTA), is the creation of a specialty in clinical pathology for veterinary technicians.
Basic Concepts and Terminology
Quality Assurance (QA)
In the clinical laboratory context, QA refers to programmatic efforts to minimize all types of error (see below). A QA program typically includes a laboratory quality manual; goals; standard operating procedures; internal and external monitoring; and appropriate evaluation of new methods.
Quality Control (QC)
In the clinical laboratory context, QC usually refers to the specific steps taken to minimize analytical error. An example of laboratory QC is the appropriate use of quality control materials, i.e., substances containing established amounts of the analyte(s) in question - to ensure that the assay system is performing properly.
Three main types of error affect laboratory test results:
Pre-analytical error occurs before the test is ever run. Common examples of pre-analytical error include problems attributable to sample handling or collection, and labeling of tubes or other specimen containers with improper patient information.
Analytical error occurs when there is a problem with the test itself, whether due to failure of an automated function (for example, sample aspiration), a reagent problem, or human error. Analytical error can be divided into random error (i.e., imprecision) and systemic error (bias).
Post-analytical error occurs after the test has been performed. The most common examples are transcriptional or data entry errors, such as transposing numbers (for example, "901 instead of "109") or entering the correct value in the wrong patient's medical record.
Total Allowable Error (TEa)
No analytical method is perfect, but how much error is acceptable? Quality requirements for laboratory tests are often expressed as TEa, to indicate the degree of change in a test value required to affect clinical decision-making.
TEa varies greatly between analytes - for example, small changes in serum electrolyte concentrations are likely to be clinically significant, whereas small changes in serum liver enzyme activities are not. Thus, we should tolerate more error (TEa should be higher) in an assay for alanine aminotransferase than in an assay for potassium.
There is no current consensus in veterinary medicine about TEa for commonly measured analytes in common domestic species. This is an identified area of need.
Recent Veterinary Investigations of Analytical Performance
A recent study evaluated analytical performance of biochemistry testing by in-clinic chemistry analyzers and by reference laboratories. The results showed significant variation in analytical performance of in-clinic analyzers, even among those of the same type; moreover, for both in-clinic analyzers and reference laboratories, analytical error exceeded proposed TEa standards for some analytes.
Another recent study evaluated analytical performance of a dry chemistry analyzer designed for in-clinic use and found that 13 of 16 analytes (81%) met the proposed quality requirement - performance similar to that of other small benchtop chemistry analyzers.
Analytical performance of in-clinic laboratory instruments requires further investigation. Identified important shortcomings in performance should be addressed by manufacturers, with input from other segments of the veterinary community.
1. ASVCP Quality and Laboratory Standards guidelines: www.asvcp.org/pubs/qas/
2. Bellamy JEC, Olexson DW, Quality Assurance Handbook for Veterinary Laboratories. Ames: Iowa State University Press; 2000.
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7. NAVTA announcement of The Academy of Veterinary Clinical Pathology Technicians as a recognized specialty: www.navta.net/press/navta-announces-11th-veterinary-technician-specialty.
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