The chemical composition of blood, urine, spinal fluid, sweat, provides a wealth of information on the well being or illness of the individual. The presence, concentration, and activity of chemical constituents are indicators of various organ functions. Concentrations higher or lower than expected sometimes require immediate attention. Some of the reasons to analyze body fluids.
1. Screening of an apparently healthy population for unsuspected abnormalities.
2. Confirming or ruling out a diagnosis.
3. Monitoring changes during treatment, improvement of condition or lack of improvement.
4. Detecting or monitoring drug levels for diagnosis or maintenance of optimal therapeutic levels.
By the 1950s, demands of clinicians for laboratory tests increased rapidly. Classical methods of manual laboratory techniques could not keep up with these demands. The cost of performing large numbers of laboratory tests by manual methods became staggering and the response time was unacceptable.
The article in the first edition of this Encyclopedia published in 1988 describes the history of laboratory instrumentation during the previous three decades (1). Reviewing that long list of automated instruments, with the exception of a few, all became museum pieces. During the last 15 years the laboratory landscape changed drastically. In addition, new group of automated instruments were introduced during this period. They were developed to perform bedside or near patient testing, collectively called Point of Care Testing instruments. In this period in addition to new testing instruments, perianalytical instrumentation for specimen handling became available. Their combined result is increased productivity and reduction of manpower requirements, which became imperative due to increased cost of healthcare and dwindling resources. This article will present some financial justification of these investments.
PATIENT PREPARATION, SPECIMEN COLLECTION, AND HANDLING
The prerequisites for accurate testing include proper patient preparation, specimen collection, and specimen handling. Blood specimens yield the most information about the clinical status of the patient though in many cases urine is the preferred sample. For specialized tests, other body fluids that include sweat and spinal fluid are used. When some tests, such as glucose and lipids, require fasting specimens, patients are prepared accordingly.
Common errors affecting all specimens include the following:
Inaccurate and incomplete patient instructions prior to collection.
Wrong container/ tube used for the collection.
Failure to label a specimen correctly.
Insufficient amount of specimen to perform the test.
Specimen leakage in transit due to failure to tighten specimen container lids.
Interference by cellular elements of blood.
Phlebotomy techniques for blood collection have considerably improved with better gauge needles and vacuum tubes for collection. The collection tubes are color coded with different preservatives so that the proper container can be used for a particular analyte. The cells should be separated from the serum by centrifugation within 2 h of collection. Grossly or moderately hemolyzed specimens may be unsuitable for certain tests. If not separated from serumor plasma, blood cells metabolize glucose and produce a false decrease of ~ 5%/h in adults. The effect is much greater in neonates (2). If there is a delay in separating the cells from the serum, the blood should be collected in a gray top tube containing sodium fluoride as a preservative that inhibits glycolysis.
Urine collection is prone to errors as well, some of which include (3):
Failure to obtain a clean catch specimen.
Failure to obtain a complete 24 h collection/aliquot or other timed specimen.
No preservative added if needed prior to the collection.
Once specimens are properly collected and received in the clinical laboratory, processing may include bar coding, centrifugation, aliquoting, testing and reporting of results.