Clinical Chemistry

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Clinical chemistry (also known as chemical pathology, clinical biochemistry or medical biochemistry) is the area of clinical pathology that is generally concerned with analysis of bodily fluids.

A clinical chemist uses chemistry to evaluate patient health. He or she may evaluate blood, study DNA, examine tissue, or study cells. He or she may be a research scientist or a developer of diagnostic technology. Clinical chemists have traditionally worked in laboratories, but they also work in academic environments or in industry.

Clinical chemists research and develop laboratory procedures that help physicians make earlier, more precise diagnoses and tailor therapy for patients. As technology develops — in “hot” areas like molecular biology or transplant medicine, for example — clinical chemists apply their knowledge to develop practical applications of these advances.

The discipline of clinical chemistry originated in the late 19th century with the use of simple chemical tests for various components of blood and urine. Subsequent to this, other techniques were applied including the use and measurement of enzyme activities, spectrophotometry, electrophoresis, and immunoassay.

Most current laboratories are now highly automated to accommodate the high workload typical of a hospital laboratory. Tests performed are closely monitored and quality controlled.

All biochemical tests come under chemical pathology. These are performed on any kind of body fluid, but mostly on serum or plasma. Serum is the yellow watery part of blood that is left after blood has been allowed to clot and all blood cells have been removed. This is most easily done by centrifugation, which packs the denser blood cells and platelets to the bottom of the centrifuge tube, leaving the liquid serum fraction resting above the packed cells.

This initial step before analysis has recently been included in instruments that operate on the “integrated system” principle. Plasma is in essence the same as serum, but is obtained by centrifuging the blood without clotting. Plasma is obtained by centrifugation before clotting occurs. The type of test required dictates what type of sample is used.

A large medical laboratory will accept samples for up to about 700 different kinds of tests. Even the largest of laboratories rarely do all these tests themselves, and some must be referred to other labs.

This large array of tests can be further sub-categorized into sub-specialties of:

  • General or routine chemistry – commonly ordered blood chemistries (e.g., liver and kidney function tests)
  • Special chemistry – elaborate techniques such as electrophoresis and manual testing methods
  • Clinical endocrinology – the study of hormones, and diagnosis of endocrine disorders
  • Toxicology – the study of drugs of abuse and other chemicals
  • Therapeutic drug monitoring – measurement of therapeutic medication levels to optimize dosage
  • Urinalysis – chemical analysis of urine for a wide array of diseases, along with other fluids such as CSF and effusions
  • Fecal analysis – mostly for detection of gastrointestinal disorders

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