Clinical chemistry

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

The discipline originated in the late 19th century with the use of simple chemical tests for various components of blood and urine. Subsequently 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 which operate on the"integrated system" principle. Plasma is essentially 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 need to be referred to other labs.

This large array of tests can be further sub-categorised into sub-specialities of:

• General or routine chemistry - commonly ordered blood chemistries (e.g. liver and kidney function tests).
• Special chemistry - elaborate techniques such as electrophoresis manual testing methods.
• Clinical endocrinology - the study of hormones, and diagnosis of endocrine disorders.
• toxicology - the study of drugs of abuse.
• Therapeutic Drug Monitoring - measurement of therapeutic medications blood 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.

Tests

Common clinical chemistry tests include:

-Electrolytes

• Sodium;
• Potassium;
• Chloride;
• Bicarbonate;

-Renal (Kidney) Function Tests

• Creatinine;
• Blood urea nitrogen;

-Liver Function Tests

• Total protein (serum);
  • Albumin;
  • Globulins;
  • A/G ratio (albumin/globulin)
  • Protein electrophoresis
  • Urine protein
• Bilirubin; direct; indirect; total
• Aspartate transaminase (AST);
• Alanine transaminase (ALT);
• Gamma-glutamyl transpeptidase (GGT);
• Alkaline phosphatase (ALP);

-Cardiac Markers

• Troponin
• Myoglobin
• CK-MB
• B-type natriuretic peptide (BNP)

-Minerals

• Calcium;
• Magnesium;
• Phosphate;
• Potassium;

-Blood Disorders

• Iron;
• Transferrin;
• TIBC
• Vitamin B12
• Folic acid

-Miscellaneous

• Glucose;
• C-reactive protein;
• Glycated hemoglobin (HbA1c);
• Uric acid;
• Arterial blood gases ($[H^+], P_{{\mathrm{CO}}_2} , P_{{\mathrm{O}}_2}$);
• Adrenocorticotropic hormone (ACTH);
• Toxicological screening and forensic toxicology (drugs and toxins);
• Neuron specific enolase (NSE);
• fecal occult blood test (FOBT);

Panel tests

A set of commonly ordered tests are combined into a panel:

• Basic metabolic panel (BMP) - 7 tests - sodium, potassium, chloride, bicarbonate, blood urea nitrogen (BUN), creatinine, glucose
• Comprehensive metabolic panel (CMP) - 14 tests - above BMP plus calcium, total protein, albumin, alkaline phosphatase (ALP), alanine amino transferase (ALT), aspartate amino transferase (AST), bilirubin

See also

• Reference ranges for common blood tests
• Medical technologist

References

Further reading

Burtis, Carl A.; Ashwood, Edward R.; Bruns, David E. (2006). Tietz textbook of clinical chemistry (4th ed.). Saunders. pp. 2448. ISBN 978-0-7216-0189-2. 

External links

• American Association of Clinical Chemistry