2. Principles in laboratory quality assurance and errors
Blood Academy August 19, 2024
Quality assurance in laboratory medicine is a collective responsibility involving clinicians, laboratory personnel, and those involved in blood sample collection. Ensuring the validity of the sample and reducing potential errors throughout its journey is paramount.
Principles
To produce reliable patient results, four fundamental principles must be considered: precision, accuracy, sensitivity, and specificity. These principles are explained below in Figure 2.1.
Consequences of Errors
Laboratory testing errors can profoundly impact clinical care, and minimising these errors is crucial for the well-being of patients and healthcare professionals.
- Diagnosis Delays: Errors can cause delays in diagnosis if the sample needs to be retaken.
- Anxiety: Retesting and uncertainty can increase anxiety for both the operator and the patient.
- Additional Sampling: In some cases, new samples may be needed, adding complexity and potential discomfort.
- Risk Mitigation: Minimising risks is crucial to safeguard patient well-being and avoid missing critical diagnostic or screening opportunities.
- Patient Reluctance: Some patients may be reluctant to undergo repeated sampling, further emphasising the importance of accuracy in blood collection and analysis.
Phases of Potential Errors
To better understand potential sources of errors, it is helpful to categorise them into three distinct phases: pre-analytical, analytical, and post-analytical. Each stage represents a different segment of the sample’s journey from collection to reporting, and each has its own set of potential errors. A large study⁵ in a clinical laboratory found that approximately 62% of errors were pre-analytical. In contrast, post-analytical errors constituted around 23%, and analytical errors within the laboratory were relatively minimal.
Pre-Analytical Errors
This phase covers everything that happens before the blood sample is taken and analysed. Often, this phase is the most prone to errors, but fortunately, these errors are generally easier to rectify. They can include issues like improper blood collection techniques leading to haemolysis, incorrect or incomplete filling of the request form, and misidentification of patient details. The loss or misplacement of the request form is also a notable concern in this phase. Pre-analytical errors are the most common sources of error in laboratory medicine. Most errors occur before the sample reaches the laboratory, including misidentifying the patient, inaccuracies in the request form, or taking blood from the wrong patient. While significant, these errors are generally easier to identify and resolve than those at later stages.
Analytical Errors
Analytical errors occur when the sample has reached the laboratory and is in the process of being analysed. Errors in this phase can stem from a variety of sources, such as equipment malfunction, operator error, or issues with laboratory reagents, including their expiry. Ensuring proper equipment maintenance and calibration, along with rigorous staff training and adherence to protocols, is crucial in minimising these errors.
Post-Analytical Errors
After the laboratory has issued the test results, errors can still occur. These might include misinterpretation of results, incorrect data entry, or errors in transmitting results to the healthcare provider. Ensuring accuracy in this phase is vital, as it directly impacts clinical decision-making. Misinterpretation of results can arise due to various factors, including a lack of familiarity with the test or an incorrect understanding of applying the results clinically. Another common issue in the post-analytical phase is the transcription of results from one system to another, which inherently carries the risk of introducing human errors. Minimising transcription where possible and involving experienced personnel in result interpretation can mitigate these risks.