CMP Blood Test - More Information

The comprehensive metabolic panel test, also known as the CMP test, CMP lab test, comprehensive metabolic panel blood test and the CMP blood test, is a commonly ordered blood panel that checks levels of various important metabolites and electrolytes in the blood.

Previously, the CMP lab test has also been referred to as a chemistry panel, Chem 14 and SMAC (sequential multiple analyzer chemistry) although most of these terms are out of date. The CMP test consists of, as the name suggests, a relatively comprehensive set of screening lab tests. The lab panel checks for abnormalities in a number of organs, including the kidney and liver. Additionally, the comp metabolic panel is helpful for screening for diabetes (blood glucose level), acid-base disturbances, dehydration (BUN / creatinine ratio), protein imbalances and electrolyte abnormalities.

The CMP blood test includes the sodium test, potassium test, chloride test and CO2 blood test. Sodium is an important element that plays an important role in nerve function and fluid balance in the body. Water imbalances in the body that cause high sodium levels (hypernatremia) as well as low sodium levels (hyponatremia) require active management. Potassium plays a vital role in nerve cells and low potassium (hypokalemia) and high potassium (hyperkalemia) levels can be life-threatening if not addressed. Chloride is a negatively charged element that helps balance out the body's acidity as well as maintain an appropriate fluid balance. Carbon dioxide is an electrolyte that helps buffer acidity in the body and frequently shifts into other forms (e.g. bicarbonate) to do so. Together, these electrolytes are intimately related and work synergistically, and imbalances in one or more electrolytes can lead to a variety of acid-base and metabolic disorders. The CMP lab panel also checks the glucose test as a screen for diabetes.

The CMP test also measures several blood markers related to kidney function. This test includes the creatinine test but also adds additional information by measuring the blood urea nitrogen, or BUN, blood level. Creatinine is released into the blood after muscle cells are naturally broken down in the body. Creatinine blood levels are sensitive to kidney function and tend to rise when the kidney is not working properly. Blood urea nitrogen is a byproduct of the liver and increased levels suggest impaired renal health. BUN levels can rise with low blood volume, severe infections, dehydration and high protein diets. The BUN / creatinine ratio is sometimes used as a ratio between these blood markers to get a relative sense of flow through the kidney. A ratio >20:1 may indicate dehydration or low flow through the kidney while a ratio <10:1 may imply some other form of kidney problem related to decreased BUN reabsorption.

One interesting calculation reported with the comprehensive metabolic panel is the estimated glomerular filtration rate, or eGFR. The eGFR is valuable for screening for kidney disease or monitoring the progress of kidney dysfunction in someone with known kidney problems. The eGFR is calculated using the creatinine level and specific characteristics of the patient such as race, age and sex. As can be seen on the sample CMP lab report, a normal eGFR is > or = 60 ml/min/1.73m2. This metric, in conjunction with the BUN and creatinine levels reported on the CMP test, provide a valuable snapshot of kidney health.

Another interesting calculation that can be made using components reported in the CMP blood test is the anion gap. The anion gap measures the difference between positively charged ions and negatively charged ions and is helpful as a way to identify acid imbalance issues in the blood such as metabolic acidosis. The standard anion gap calculation is performed by taking the sodium - (chloride + bicarbonate) from the lab results. Although the anion gap is sometimes calculated using the potassium result, most people calculate it without it. A normal anion gap is typically 6-12 meq/L.

When considering this lab test, some people want to know how it differs from the BMP, or Basic Metabolic Panel. In comparing the CMP versus the BMP blood tests, the comprehensive metabolic panel is actually a more comprehensive form of the basic metabolic panel test because it also includes a set of liver function tests. Thus, for many people, the CMP test is of greater interest given the information it adds about the health of the liver. Because it provides a snapshot across a wide range of organ systems, the CMP test is frequently ordered with the CBC test and the lipid panel as part of annual screening exams that involve routine blood work. Many people who are interested in a panel of wellness screening tests order the wellness 1 test panel.

CMP Lab Test - Process & Results

The comprehensive metabolic panel is often ordered as part of a routine or annual physical. This blood test is also frequently ordered as part of a basic screen for most Emergency Room patients. Ideally, an 8-12 hour fast is performed before getting a CMP blood test done but this does not always occur, particularly in emergencies. Because the CMP test is so commonly performed, getting a comprehensive metabolic panel test near you is typically an easy process. Any lab locations with standard lab equipment can perform the blood test and it usually only requires a small amount of blood (<2 mL) to perform the test.

Once the CMP lab results are ready, they will be available for electronic download. As can be seen on the sample CMP lab report above, the individual components of the comprehensive metabolic panel blood test are reported as numerical values and can be compared against the reference ranges provided by the Quest Diagnostics.