Quality Management System

Medical laboratory of the future

Quantum Diagnostics is committed to providing fast turnaround times, high quality reporting and evolving into the “medical laboratory of the future”. Apart from listening to our clients, brainstorming with new ideas and new ways to deliver the best service, we are also committed in stringent internal quality control procedures and practices.

Validity & Reliability of Test Results

The validity and reliability of test results are dependent on a number of variables:

  1. Pre-analytical variables include physiological factors, patient preparation, specimen collection and transport.
  2. Analytical variables include the precision and accuracy of the test method and factors which may interfere with a particular assay e.g. lipaemia, in vitro haemolysis and medication.
  3. Post analytical variables include data entry and calculations by laboratory staff, result validation, interpretation of the results, data transfer and the method used to report the results (electronic, paper or telephone).

How does the Laboratory Control Variables

The laboratory controls the impact of these variables, as far as possible, by two processes:

  1. Quality Control

    On each occasion that the patient samples are tested, the laboratory also tests ‘controls’ with known concentrations of analyte or cells, of known reactivity in the test system.

    The control levels are such that they control the entire analytical range and are “matrix matched” i.e.
    Urine based control material is used to control urine assays, serum based controls are used to control serum assays and whole blood controls are used to control whole blood assays.

  2. Quality Assurance

    All Quantum laboratories participate in external quality assurance programs in which the results from each laboratory are compared to the results obtained by a group of laboratories as well as known values.Quality assurance also requires laboratories to attend to within lab pre-analytical and post-analytical variables.

Variables outside the Laboratory Control

Quality control and quality assurance help maintain both the accuracy and the consistency of laboratory results but absolute accuracy is not technically possible. Variables cannot be entirely avoided and the interpretation of any results must take these factors into consideration.

  1. Selection of Test(s)

    Discretionary testing is the selection of a single test, or a small number of tests on the basis of the clinical findings.

    Profile testing is the ordering of test as ‘screening test’ and may involve a ‘battery’ of tests.

    In a normal individual, the greater the number of tests performed, the greater is the chance of finding at least one abnormal result. Isolated slightly abnormal results are often of no clinical significance, however if clinically indicated after explanation to the patient, it may be prudent to check these after a few days or weeks depending on the analyte.

  2. The Specimen

    The laboratory results are dependent on the quality of the specimen which it receives for example an inadequate biopsy or a poor cervical smear results in an incomplete and possible inaccurate opinion.

    In other circumstance, an inaccurate volume of blood in a sodium citrate or EDTA tube, or improper collection of urine may cause inaccurate reporting. E.g. For urine FEME and culture, it is crucial that a Mid-Stream Specimen of urine is collected (MSSU) for accurate results.

  3. The Request Form

    Provision of appropriate clinical information is essential if the pathology laboratory is to assess the results and their likely significance. Any difficulty in obtaining the specimen should also be noted on the request form as they may affect the test result. It is also essential that all requested information is filled in adequately on the request form.

Quantitative Test Results and the Reference Interval

Generally reference intervals represent the test results which would be obtained in the normal population and are based on the results obtained on a series of normal ‘healthy’ individuals. Other reference ranges may be specific e.g. lipids and glucose which are evidence based with respect to disease prevention.

The reference intervals quoted generally lie between the 2.5 and 97.5 percentiles for the group which they were derived. Age, gender, race and test methodology are important variables so the reference intervals quoted in the literature may not be generally applicable. Wherever possible laboratories establish their own reference intervals but this is not always feasible. As the reference interval represents the 2.5 to 97.5 centiles, inevitably 5% of entirely normal people will have test results outside the reference interval. Minor variations should thus be interpreted with caution.

The Sensitivity and Specificity of a Qualitative Test

The ability of a test to discriminate between normal and abnormal individuals is described by its sensitivity and specificity. Test sensitivity is defined as the percentage of people with a specific disease who have an abnormal test result.

The specificity is defined as the percentage of people without the disease who have a normal result. Generally, the balance of sensitivity and specificity is a major consideration in the choice of a test methodology. This balance must consider the ability of the test not to have false negatives and the ability not to produce false positives. Most screening test employed will be biased towards reducing false negatives which may lead to a very few unaffected individuals having false positive results – this is particularly evidenced in assays such as HIV, Hepatitis B & C and cancer markers. Should the results not "fit" the clinical picture, please do not hesitate to discuss with our senior scientific staff.

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