How Reliable is Laboratory Testing?

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For many people, clinical laboratory testing is an invisible side of medical care. Yet many of the decisions that doctors make about your health – diagnosing the cause of symptoms, developing a course of action and a treatment plan, or monitoring your body's response to therapy – are based on laboratory data.

Your doctor trusts laboratory results. That trust is well placed. Clinical laboratory testing has to meet very high standards.

  • A test method must meet rigorous criteria before it can be used in clinical practice. In the European Community, all In-Vitro Diagnostic Devices (IVDs) must have a CE mark to show that they are fit for purpose. To obtain CE marking, the manufacturer must show that the product meets essential requirements designed to ensure that the product does not compromise the health and safety of patients and users, and that it is designed and manufactured to achieve the performance specified by the manufacturer for the stated medical purpose. In the UK, the Medicines and Healthcare Products Regulatory Agency is the regulatory body for IVDs
  • A laboratory must demonstrate that it is able to perform tests in a clinically acceptable way. A professional accrediting organisation, Clinical Pathology Accreditation (CPA) (UK) Ltd, monitors laboratories and sets standards that a laboratory must meet in order to be accredited to perform clinical testing. Some of these standards are:
    • Laboratories must conduct routine quality control tests, usually every day, to assure that the test method and equipment are performing to standards. These are carried out by analyzing materials of known composition to ensure the laboratory is producing reliable results.
    • Laboratories participate in external quality assessment (EQA) schemes. In these schemes, an external organisation sends samples to be tested “blind” – i.e. the laboratory does not know the expected result. The laboratory must report results back to the organisation. EQA schemes provide independent, objective data on individual laboratory and test method performance, and can help laboratories identify real or potential problems. If the laboratory repeatedly fails to get the right result, it will receive a poor performance notification from the external organization, and failure to respond to this notification will jeopardize the laboratory’s accreditation status.
    • Laboratories must demonstrate that they have policies and procedures in place to help ensure that the sample is collected and handled in an appropriate way and that results are reported with information to help with interpretation of the result.

These requirements ensure that the tests performed by clinical laboratories for patient care will produce results that can be trusted.  

Some of the statistical indicators that are used to ensure that both the test method and the laboratory are meeting acceptable standards, are described in the next few pages. The links to other Lab Tests Online pages provide additional information on specific concepts and practices that contribute to the quality of laboratory tests.  

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