It is often assumed that errors in laboratory testing are more likely to occur in the analytical stage. As a result, laboratories invest in high quality laboratory equipment that deliver accurate, consistent results, and spend a lot of time and effort in adhering to quality control programs, taking part in laboratory inspections, and ensuring compliance with industry standards and government regulations. In fact, such measures have greatly improved accuracy in the analytic phase.
However, as opposed to popular belief, it is the preanalytic phase that is more error prone. Errors in this phase can occur in patient variables (age, race, sex, pharmacogenomics, and surgical or medical comorbidites) as well as in specimen variables during collection, handling, and processing. Some patient variables can be controlled while others cannot be controlled. Errors in specimen variables are difficult to identify and correct. Of the controllable preanalytic phase variables, specimen collection is considered to be the most critical. Most preanalytic errors occur due to
- Sample misidentification leading to unacceptability
- Inefficiency in blood sample draw
- Lack of sufficient volume to perform the assay
- Incorrect whole blood to anticoagulant ratio
- Specimen quality issues – hemolyzed specimens, or those that are clotted, contaminated, or collected in the wrong container
A recent report highlights the effect of blood collection tubes (BCTs) on preanalytic errors. According to the report, the components of BCTs such as tube walls, rubber stoppers, lubricants, anticoagulants, separator gels, clot activators, and surfactants affect the quality of specimens and accuracy of laboratory tests. These factors can influence the measurement of serum and plasma by affecting the stability of analytes in blood specimens or by adding constituents to blood, adsorbing elements, and interacting with protein and cellular components.
To avoid these issues, clinical labs need to have measures in place to evaluate the interferences from collection device components in clinical tests. Using high quality blood collection sets and BCTs is also critical. For instance, research has shown that samples collected into the Polyethylene Therephthalate (PET) or EDTA tubes provided accurate ABO and Rh typing results that remained consistent over a 28-day period and that the samples also appeared to allow accurate alloantibody identification.
Specimen handling from patient to laboratory is also an area of potential error but usually outside control of the clinical laboratory. To maintain the quality of the specimen, it is critical that the sample should be handled carefully during transport and processing. Exposure to heat and cold, vibration, position of specimen tubes, and delivery time can significantly affect test results.
Minimizing pre-analytical errors can improve the quality of blood test results, avoid the need for specimen re-collection, reduce turnaround time, and improve patient management.