Indications and Procedures (Magill’s Medical Guide, Sixth Edition)
Clinical laboratory testing is a vital element in diagnosis. After physical examination and the taking of the patient’s medical history, the physician will often request that specific tests be performed on blood, urine, or other body fluids. Appropriate specimens are collected and forwarded to the laboratory for specimen processing.
Blood is the most common specimen submitted for testing in the clinical laboratory. In a hospital or large referral laboratory, there may be special personnel, called phlebotomists, employed to collect blood. In a small office laboratory, blood may be collected by the attending physician or nurse. Blood is collected in a syringe or in special tubes that may contain anticoagulants.
Urine is the next most common laboratory specimen and is collected as a result of a single void (random urine specimen) or for a time period of twenty-four hours or more. In the latter case, the collection container may also contain substances that act as a preservative. If a long-term urine specimen is necessary, it is very important for the patient to follow the directions regarding collection. Failure to follow these directions can lead to erroneous laboratory results.
Less commonly collected specimens include cerebrospinal fluid, gastric (stomach) fluid, and amniotic fluid. Cerebrospinal fluid is usually collected by a physician by direct sampling with a needle (lumbar puncture, or spinal...
(The entire section is 1104 words.)
Uses and Complications (Magill’s Medical Guide, Sixth Edition)
Because of the variety of laboratory testing, it is impractical to cover its applications in depth in a brief review. Instead, a few illustrative tests that are performed often or are associated with familiar disorders will be presented. The most frequently ordered laboratory tests are serum glucose tests, serum electrolyte (salt) level measurements, and complete blood count (CBC) tests.
The maintenance of blood glucose (sugar) levels is essential for body activity and brain function. The laboratory measurement of blood glucose is one of the oldest known procedures performed in the clinical laboratory. It is part of the diagnostic procedures used to monitor and test for diabetes mellitus. Glucose and electrolyte testing are performed in the chemistry section of the laboratory, while a CBC takes place in hematology. Certain levels of electrolytes—sodium, chloride, potassium, and calcium—are needed for proper cardiac function. An abnormal level of these salts could also indicate possible hormonal or kidney malfunction. The CBC is a measure of the cell populations that carry oxygen (red blood cells), fight infection or invasion by foreign substances (white blood cells), and activate the blood-clotting mechanism (platelets). The white cell population is elevated in infections but also in cases of leukemia (malignant growth of a white cell population). More specialized testing is needed when leukemia is suspected. An...
(The entire section is 1199 words.)
Perspective and Prospects (Magill’s Medical Guide, Sixth Edition)
According to a 2002 study of the history of the clinical laboratory by J. Büttner, the concept of the modern hospital laboratory was first documented in 1791 when French physician and chemist Antoine-François de Fourcroy wrote that in hospitals “a chemical laboratory should be set up not far away from a ward having twenty or thirty beds.” Büttner asserts that the two suppositions necessary for the creation of these laboratories were the idea that the results of laboratory examinations can be used as “chemical signs” in medical diagnosis and a new concept of disease that was the result of the “birth of the clinic” at the end of the eighteenth century.
During this phase of laboratory development, investigations were performed at patients’ bedsides by physicians themselves. In the period from 1840 to 1855, clinical laboratories were established as operations distinct from hospitals and clinics. Most of these laboratories were developed in German-speaking countries and staffed by scientists who performed tests for the hospitals and taught medical students physiological chemistry. From 1855 onward, the concept of the clinical laboratory spread rapidly, with clinicians assuming directorship roles. The laboratory ultimately serving as a model for clinical laboratories in the United States was established by the renowned pathologist Rudolf Virchow at Berlin University. As the chair for pathological anatomy,...
(The entire section is 558 words.)
For Further Information: (Magill’s Medical Guide, Sixth Edition)
Bennington, James L., ed. Saunders Dictionary and Encyclopedia of Laboratory Medicine and Technology. Philadelphia: W. B. Saunders, 1984. An excellent reference to laboratory vocabulary and terminology. Gives detailed information about complicated procedures and topics, rather than simple dictionary definitions.
Cavanaugh, Bonita Morrow. Nurse’s Manual of Laboratory and Diagnostic Tests. 4th ed. Philadelphia: F. A. Davis, 2003. Provides information on hundreds of laboratory and diagnostic tests, with each test presented in two distinct, cross-referenced sections: “Background Information” sections provide a complete description of each test and its purposes; “Clinical Application Data” sections focus on the information nurses most commonly need while caring for clients.
Griffith, H. Winter. Complete Guide to Symptoms, Illness, and Surgery. Revised and updated by Stephen Moore and Kenneth Yoder. 5th ed. New York: Perigee, 2006. Covers more than five hundred diseases and disorders and includes information about causes and risk factors, preventive techniques, and diagnostic tests.
McPherson, Richard A., and Matthew R. Pincus, eds. Henry’s Clinical Diagnosis and Management by Laboratory Methods. 21st ed. Philadelphia: Saunders/Elsevier, 2007. The classic text on the clinical laboratory. Multiple authors cover all aspects of laboratory operations, including...
(The entire section is 335 words.)