Quality assurance tips for your clinical laboratory (Proceedings)
We have discussed the basic methods behind hematology and biochemical instrumentation and some concepts related to instrument selection and calibration in the previous sessions. What needs to be done to insure confidence in your results is next. Explanations of quality assurance, quality control, requirements and guidelines, and some practical recommendations how to initiate and maintain them will be shared in this session.
Quality assurance (QA)QA, as it relates to the clinical laboratory, is an all encompassing program for the systematic monitoring and evaluation of the various aspects of producing laboratory results to ensure that standards of quality are being met. These aspects are traditionally divided into three phases: preanalytical, analytical, and postanalytical. Portions of these phases will be discussed in more detail in the "Lab Errors" session. This session will focus on aspects more specifically related to the analytical phase. Since analyzers are comprised of numerous pieces and parts like lamps, tubing, electronics, and reagents that can wear, leak, plug, precipitate, become contaminated, etc. over time, regular monitoring is necessary.
Regulations, requirements, and suggestions
While human laboratories and the equipment therein are highly regulated, similar regulation is lacking in the veterinary field. This provides ample opportunity for a lack of education, experience, and/or commitment to interfere with producing quality results. The following selected requirements have been summarized from those posted on The American Animal Hospital Association website ( http://AAHAnet.org/): 1) Annual laboratory proficiency testing and appropriate corrective action is documented. 2) Use of written protocols to ensure the accuracy of tests performed in the practice. 3) Annual CE in laboratory procedures.4) Periodic QC tests are run using pre-assayed control material, if available, for each test routinely performed in the practice. 4) QC evaluations are performed and documented at least daily for automated hematology, weekly for serum chemistry, and monthly for urinalysis. 5) Consistent procedures to identify and record artifacts, such as hemolysis, lipemia, etc. 6) The practice uses an external QA (laboratory analysis) program through an accredited external laboratory or proficiency testing service.
The above is an excellent start to a good QA program, but portions of it are impractical and the comment "if QC is available" in item 4 leaves a loophole for both users and manufacturers. The American Society of Veterinary Clinical has developed QA standards for rePathology ference laboratories and is in the process of refining them for clinic use. In addition, others are working through the VIN network to establish some recommendations. Further explanations and recommendations for some additional confirmatory assessments are described below.
Quality control (QC)
In laboratory lingo, "QC" typically refers to commercial material prepared to mimic patient samples when run on specific pieces of equipment. For example, a large batch (lot) of material, comprised of fixed erythrocytes with particles added to mimic leukocytes and platelets, is produced and analyzed in order to establish a defined target value and acceptable range of results for a specific analyzer or group of analyzers (i.e. impedance-based). Aliquots are dispensed into small vials for shipment to participating users. These materials have a defined shelf life and target values will change between lots. Following the instructions in the package insert related handling the material is crucial to its effective use. QC materials cannot be exchanged between impedance and flow/laser based equipment. In a similar fashion, cell-free material is generated for testing with biochemical and other analyzers. Typically, two to three "levels" containing low, normal or high concentrations of the analytes of interest are available.