Types of Biological Tests

3 Key excerpts on "Types of Biological Tests"

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  eBook - ePub

  An Introduction to Biomedical Science in Professional and Clinical Practice

  • Sarah Jane Pitt, Jim Cunningham(Authors)
  • 2013(Publication Date)
  • Wiley

    (Publisher)

  Patients whose specimens require pathology investigations often present with common and fairly non-specific symptoms, such as pyrexia (fever), lethargy (tiredness) and purpura (rash). A range of tests might be necessary to narrow down the possible causes (‘differential diagnosis’) and this might involve some or all pathology disciplines. Sometimes the tests are performed simultaneously, whereas in other situations the results from one laboratory suggest that further tests are required which involve another discipline. For example, in the case of a child with suspected meningitis, cerebrospinal fluid (CSF) would be taken and aliquots sent to the biochemistry and the microbiology laboratories at the same time. The biomedical scientist in biochemistry would test for glucose and protein whereas the microbiology biomedical scientist would count the white blood cells and do specific rapid tests to identify any bacteria present (e.g. prepare a slide and stain with Gram stain). In this way, a diagnosis can be made quickly and, if the child does have bacterial meningitis, they can be given the appropriate treatment as soon as possible. However, in the case of a person infected with hepatitis, the tests might be done in stages. The symptoms that a patient with hepatitis has can sometimes be very non-specific and when they first visit their doctor, it may not be obvious. Liver function tests (LFTs) might be included in a general set of tests to find out why the patient is unwell. If the results indicated that the patient could have infectious hepatitis, then a further blood sample would be taken and sent to the microbiology (or virology) laboratory, where the exact cause can be identified.

  6.7 Evaluation of a new diagnostic test

  New assays are regularly produced for clinical pathology laboratories thanks to both scientific and technological breakthroughs. For example, cell surface and serological markers, which provide a more precise diagnosis or indicate a prognosis in certain cancers, are discovered intermittently. Occasionally new diseases arise which are caused by previously unknown agents, such as human immunodeficiency virus, the cause of HIV/AIDS, both of which were described for the first time in the early 1980s. Sometimes the novel finding is the source of a well-known disease; a good example of that is the recognition that the bacterium Helicobacter pylori

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  Cancer

  Basic Science and Clinical Aspects

  • Craig A. Almeida, Sheila A. Barry(Authors)
  • 2011(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  O varian (PLCO) Cancer Screening Trial to analyze the influence of certain screening tests on mortality rates. Collectively, these four types of cancers represent almost half the number of cancer diagnoses and deaths each year. The objective of this trial is to determine whether or not particular screening tests that can detect the presence of cancer prior to a person experiencing symptoms will reduce the number of fatalities associated with these cancers when treatment occurs in the pre-symptomatic stage. Nearly 155,000 healthy men and women between the ages of 55 and 74 have been randomly assigned into one of two groups: those that receive routine checkups from their health providers, and those that receive a series of examinations that specifically screen for prostate, lung, colorectal and ovarian cancers. Study participants will be monitored through 2017 to determine if these screening tests ultimately increase the survival rates of such patients.

  DIAGNOSTIC PROCEDURES FOR THE CONFIRMATION OF A DISEASE

  Diagnostic tests differ from screening tests in that their purpose is to confirm that a person has a particular condition or disease.6.2 The latest laboratory tests and radiological equipment, as well as knowledge of patient history, have made it possible to make a diagnosis in a shorter period of time. Less time spent making a diagnosis provides more time to perform additional tests to obtain a better understanding of the exact condition, or to seek a second opinion, if necessary, regarding the diagnosis and treatment options.

  Blood and urine tests can indicate changes in health

  Laboratory tests performed on blood and urine are among the most critical of all clinical tools used by healthcare professionals in order to determine or rule out the presence of illness in the body. Virtually noninvasive in comparison to other procedures, they yield an enormous amount of highly specific information allowing healthcare providers to gain an understanding of how the cancer is affecting the rest of the body. Although some cancers release protein markers into the blood to confirm a diagnosis, the majority of cancers do not or the markers have not yet been identified. Patients who have symptoms such as a lump, bleeding, pain, or discomfort, or who have cancer itself, will usually have some routine clinical laboratory tests performed to rule out certain conditions, to confirm a diagnosis, or to follow the effectiveness of treatment.

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  Lecture Notes: Clinical Biochemistry

  • Geoffrey Beckett, Simon W. Walker, Peter Rae, Peter Ashby(Authors)
  • 2013(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  discretionary , meaning that the test is requested for defined diagnostic purposes, as distinct from screening, where a disease is sought without there being any specific indication of its presence in the individual. The justification for discretionary testing is well summarised by Asher (1954):

  1 Why do I request this test?

  2 What will I look for in the result?

  3 If I find what I am looking for, will it affect my diagnosis?

  4 How will this investigation affect my management of the patient?

  5 Will this investigation ultimately benefit the patient?

  The principal reasons for requesting biochemical tests are as follows (where the first two categories would be defined as discretionary):

  • To assist in diagnosis. For example, the diagnosis of diabetes mellitus is crucially dependent on the measurement and interpretation of plasma [glucose]. Biochemical tests may also aid the differential diagnosis or indicate the severity of a disease (see also Table 1.2 ).
  • In disease monitoring. A good example is the use of arterial blood gases to follow the progress of someone admitted with a severe pneumonia or creatinine in an individual with chronic renal failure (see also Table 1.2 ).
  • In prognosis or disease risk assessment. Serum cholesterol (pp. 192) or high-sensitive C-reactive protein (hsCRP) (pp. 192) are used in the assessment of cardiovascular risk, for example.
  • In screening for disease. An example here would be measurement of thyroid-stimulating hormone (TSH) to screen for neonatal hypothyroidism.
  • Miscellaneous, for example for forensic purposes or ethically approved research.

  Screening may take two forms:

  • In well-population screening a spectrum of tests is carried out on individuals from an apparently healthy population in an attempt to detect pre-symptomatic or early disease. It is easy to miss significant abnormalities in the ‘flood’ of data coming from the laboratory, even when the abnormalities are ‘flagged’ in some way. Most of the abnormalities detected will be of little or no significance, yet may need additional time-consuming and often expensive tests to clarify their importance (or lack of it). For these and other reasons, the value of well-population screening has been called into question and certainly should only be initiated under certain specific circumstances which are listed in Table 1.3

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