CHAPTER 8 Laboratory Tests
I. Introduction
A. Laboratory tests are of two main types:
1. Screening tests: used in patients with no active symptoms or signs of a health problem or disease, usually for purposes of early detection or mitigation of health risk factors for serious disease.
B. It is important for the pharmacist to have a strong knowledge of the more common laboratory tests used to guide patient diagnosis and treatment. Pharmacists are likely to review laboratory tests to assess the efficacy and the safety of medications. They may recommend testing when necessary or may be called to help interpret the results obtained from such tests. A pharmacist may be asked to help a patient understand the results of a particular test.
II. The International System of Units (SI), Conventional Units of Measure, and the Reporting of Laboratory Results
A. Around the world, laboratory tests are reported in the SI units, which are based on standard metric measurements. The United States has yet to fully adopt this system, and laboratories typically report results in traditional, customary units as well as the SI units. The reporting of both types of units typically aids communication among health care professionals of different training backgrounds or nationalities.
B. “Normal” laboratory results usually fall within a reference range of values determined by taking the usual measurements of that test found within a set and defined population of healthy individuals. For qualitative tests, results are often reported as either positive or negative for a specific finding. Quantitative tests are usually reported in terms of a reference range. For most tests, the reference range is statistically determined by the mean value plus two standard deviations. Values that fall out of the reference range or expected result are sometimes labeled “abnormal.” A value that falls outside an accepted range does not necessarily indicate the need for treatment or a need to make the value “normal.” An “abnormal” result requires interpretation in the context of the patient’s demographics, overall health status, medical examination findings, symptoms, timing and conditions of the test, and other relevant factors. A test may not produce results consistent with the results expected, and a repeat test may be needed to rule out errors in collection or processing of the test.
III. The Most Common Laboratory Tests Pharmacists Should Know (Tables 8-1 through 8-6)
A. The following sections will provide a brief synopsis and review of laboratory testing familiar to the pharmacist, including the common medical reasons the tests are monitored. The lists are not inclusive, but are representative of the tests pharmacists are most likely to encounter in their general clinical practices.
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