What is it? The Comprehensive Metabolic Panel (CMP) is a frequently ordered panel of tests that gives your doctor important information about the current status of your kidneys, liver, and electrolyte and
acid/base balance as well as of your blood sugar and blood proteins. Abnormal results, and especially combinations of abnormal results, can indicate a problem that needs to be addressed. The CMP is typically a group of 14 specific tests that have been approved, named, and assigned a CPT code (a Current Procedural Terminology number) as a panel by Medicare, although labs may adjust the number of tests up or down. Since the majority of insurance companies also use these names and CPT codes in their claim processing, this grouping of tests has become standardized throughout the United States.
The CMP includes:
Both increased and decreased levels can be significant.
Proteins
Albumin, a small protein produced in the liver, is the major protein in serum. Total protein measures albumin as well as all other proteins in serum. Both increases and decreases in these test results can be significant.
Electrolytes
The concentrations of sodium and potassium are tightly regulated by the body as is the balance between the four molecules. Electrolyte (and acid-base) imbalances can be present with a wide variety of acute and chronic illnesses. Chloride and CO2 tests are rarely ordered by themselves.
Kidney Tests
BUN and creatinine are waste products filtered out of the blood by the kidneys. Increased concentrations in the blood may indicate a temporary or chronic decrease in kidney function. When not ordered as part of the CMP, they are still usually ordered together.
Liver Tests
ALP, ALT, and AST are enzymes found in the liver and other tissues. Bilirubin is a waste product produced by the liver as it breaks down and recycles aged red blood cells. All can be found in elevated concentrations in the blood with liver disease or dysfunction.
How is the sample collected for testing?
The CMP uses a tube of blood collected by inserting a needle into a vein your arm. Ask your doctor whether you should be fasting for 10 to 12 hours prior to the blood draw. Depending on the reason for ordering the CMP, it may be drawn after fasting or on a random basis.
How is it used?
The CMP is used as a broad screening tool to evaluate organ function and check for conditions such as diabetes, liver disease, and kidney disease. The CMP may also be ordered to monitor known conditions, such as hypertension, and to monitor patients taking specific medications for any kidney- or liver-related side effects. If your doctor is interested in following two or more individual CMP components, he may order the entire CMP because it offers more information.
When is it ordered?
The CMP is routinely ordered as part of a blood work-up for a medical exam or yearly physical. Although it may be performed on a random basis, the CMP sample is usually collected after a 10 to 12 hour fast (no food or liquids other than water). While the individual tests are sensitive, they do not usually tell your doctor specifically what is wrong. Abnormal test results or groups of test results are usually followed up with other specific tests to confirm or rule out a suspected diagnosis.
