Ensuring quality is an essential requirement in laboratories. In haemostasis, the quality of results is often determined by the pre-analytical steps that constitute procedures.
In 1981 Lundberg[1] introduced the concept of the ‘brain to brain loop’ for laboratory testing. This model considers the thought processes associated with a physician caring for a patient with the initial step being the selection of laboratory tests and ending with the transmission of test results back to the physician. This model allows us to focus on quality systems within laboratory medicine and thereby segment each step of the total testing process (TTP) and ensure each step is correctly performed, thereby providing effective patient care. Using this model for describing TTP the generation of any laboratory test result involves nine steps: ordering, collection, identification, transportation, separation or preparation, analysis, reporting, and action.
Traditionally the TTP has been divided into three phases—pre-analytic, analytic, and post-analytic. More recently this has been extended to include pre-preanalytical and post post-analytical which are not directly under the laboratory’s control. Plebani[2] has estimated that errors in the phases of the TTP constitute 46-68% in the pre-pre-analytical (pre-laboratory phase), 3-5% pre-analytical, 7-13% analytical, 13-20% post-analytical and 25-46% post post-analytical (post-laboratory phase).
There are numerous pre-analytical variables which may impact on the quality and integrity of routine haemostasis testing, thereby impacting on patient management and care. With the advances in technology, automation and instrumentation we have the potential to minimise these variables, however with all areas there needs to be increased vigilance by laboratory staff and to be aware of pre-analytical variables that may impact on testing in particular, specimen collection, transportation, stability, specimen processing and storage.
Standardisation of the pre-analytical phase is critical to achieving reliable results for pathology testing in general and coagulation tests in particular, thereby reducing the side effects of influencing factors. Haemolysis, icterus and lipaemia (HIL) in patient samples may interfere with the measurement of many analytes, including coagulation parameters. Haemolysis may reflect in vitro break down of red cells due to issues arising from sample collection, transport or processing. As instrumentation becomes more sophisticated manufactures are developing instruments that are capable of evaluating HIL directly on samples prior to testing. The presence of haemolysis is a potential measure of ex vivo mishandling of samples which may impact on the integrity of results.
Pre-analytical variables have the potential for adverse impacts on patient care. Laboratory errors may have serious adverse consequences. The lack of standardised procedures for sample collection accounts for the majority of the errors within TTP. Controlling these variables is critical as they may have a direct influence on the quality of results and subsequent clinical interventions.
Although there has been, and continues to be, advances in Hospital Information systems, electronic medical records, increasing sophistication of laboratory automation and integration to both laboratory and hospital information systems there remains a potential for errors.
[1] Lundberg GD. Acting on significant laboratory results. JAMA 1981;245:1762-3.
[2] Plebani M. The detection and prevention of errors in laboratory medicine. Ann Clin Biochem. 2010;47(2):101‐110.