Clinical Chemistry
What is clinical chemistry?
Clinical chemistry uses chemical processes to measure levels of chemical components in body fluids. The most common specimens used in clinical chemistry are blood and urine. Many different tests exist to test for almost any type of chemical component in blood or urine. Components may include blood glucose, electrolytes, enzymes, hormones, lipids (fats), other metabolic substances, and proteins.
What are some common clinical chemistry tests?
The following is a description of some of the most common clinical chemistry tests (used on blood and urine specimens), including some of the uses and indications:
Blood glucose, or blood sugar, levels indicate how the body handles glucose. Measuring glucose levels after fasting can help diagnose diabetes or hypoglycemia (low blood sugar).
Electrolytes may include sodium, potassium, chloride, bicarbonate, calcium, phosphorus, and magnesium. Measuring electrolytes can specifically indicate certain metabolic and kidney disorders.
Enzymes are released into the blood by organs that are damaged or diseased. The type of enzyme released can indicate which organ is affected:
Enzyme | Organ affected |
|---|---|
Creatine kinase | Can signal damage to heart muscle or skeletal muscle CK-MB, an isoenzyme of CK, is used to distinguish heart muscle damage |
Alanine aminotransferase (ALT, SGPT), aspartate aminotransferase (AST, SGOT) | Can signal liver disorders |
Amylase and lipase | Can signal inflammation or cancer of the pancreas |
Hormones are secreted by the various endocrine glands. Raised or lowered levels of certain hormones can indicate over- or under-activity of those glands:
Hormone | Gland Affected |
|---|---|
Cortisol | adrenal glands |
Thyroxine (T4), TSH | thyroid gland |
FSH, ACTH, growth hormones | pituitary gland |
Lipids are fatty substances such as triglycerides (body fat), phospholipids (part of cell membranes), and sterols (such as cholesterol). Lipids can help signal coronary heart disease and liver disease:
Lipid | Organ affected |
|---|---|
Total cholesterol | High total cholesterol is a risk factor for cardiovascular disease (CVD) |
High-density lipoprotein (HDL or "good" cholesterol) Low-density lipoprotein (LDL or "bad" cholesterol) | High LDL cholesterol is also a risk factor for CVD High HDL cholesterol is a protective factor against CVD |
Triglycerides | High triglycerides are another independent risk factor for CVD |
Other metabolic substances can be measured to evaluate organ function:
Metabolic product | Organ affected |
|---|---|
BUN (blood urea nitrogen) Creatinine | Kidney function |
Uric acid | Can signal gout, kidney disease, and other tissue damage |
Proteins can indicate metabolic and nutritional disorders, as well as certain cancers:
Protein | Organ affected |
|---|---|
Total protein and albumin | Can signal liver or kidney disease, or malnutrition |
Globulins and the A/G ration (albumin to globulin) | Can signal infection, autoimmune disease, inflammation, and certain blood cancers |
Often, abnormal blood and urine tests are repeated to make sure there is not a sample error or lab error. Abnormal tests are often followed up by other more specialized tests.