Tests in a Comprehensive Metabolic Panel — is it broad enough?

In our previous blog, we discussed the complete blood count (CBC) test. In this post, we’ll focus on another very important general health test normally ordered as part of your annual physical exam – the comprehensive metabolic panel (CMP). The CMP test is sometimes called also comp metabolic panel test or CMP blood test, which now is also available to be purchased online direct from several lab providers. This blog will cover what is a CMP blood test, how to order it online, the tests in a Comprehensive Metabolic Panel, and whether CMP bloodwork is broad enough. CMP bloodwork can provide important information about your body's chemical balance and metabolism (the process your body is converting food to energy). The CMP blood test is mainly used to check your liver and kidney functions. Several parameters in this panel cannot be analyzed by the current at-home sample collection methods. All CMP blood tests that can be ordered without prescribing physician still require an in-person visit for a clinic or blood draw station.

Tests in a comprehensive metabolic panel
A comprehensive metabolic panel (CMP) measures 14 different parameters in your blood and can be categorized into three main groups:

1.    Glucose, Fluids & Electrolytes
Fasting Glucose is a type of sugar and your body's main energy source. Calcium is one of the body's most important minerals. Calcium is essential for the proper functioning of your nerves, muscles, and heart. Electrolytes blood work, including Sodium, Potassium, Carbon dioxide (CO₂), and Chloride. Electrolytes are minerals that have a natural positive or negative electrical charge when dissolved in water. They help your body regulate chemical reactions maintain the balance between acids and bases fluids inside and outside your cells.

2.    Liver Panel
Albumin is one of the most abundant proteins in your blood. It is made by your liver which takes proteins from the foods you eat and turns them into new proteins that circulate to various organs and tissues in your body. Albumin helps keep fluid in your bloodstream so it doesn't leak into other tissues. It gives your body the proteins it needs to keep growing and repairing tissue. It also carries vital nutrients and hormones. Albumin levels can tell how well your liver is working.

Total protein is the total amount of proteins (including albumin) found in the blood that helps determine overall nutritional status.
 
Globulins are a group of proteins that includes four types: Alpha 1, Alpha 2, beta, and gamma globulin proteins. Globulins help fight infection and move nutrients throughout your body. Some globulins are made by the liver. Others are made by the immune system.

ALP (alkaline phosphatase), ALT (alanine transaminase, also called alanine aminotransferase), and AST (aspartate aminotransferase) are different enzymes that are made by the liver. Enzymes are proteins that act as biological catalysts, which means they accelerate chemical reactions in your body. Enzymes take substrates (chemical compounds) and convert them into different molecules called products. ALP, ALT and AST are enzymes that helps break down proteins and are found mainly in your liver. If your liver is injured, it releases these enzymes into your bloodstream. Several liver diseases can be detected if you have an elevated level of your liver enzymes.
 
Bilirubin is a waste product made by the liver. It has an orange-yellow pigment that releases as part of your red blood cells’ normal breakdown. Your liver takes the bilirubin from your blood and changes its chemical make-up so that most of it goes through your poop as bile. If your bilirubin levels are higher than normal, it’s a sign that either your red blood cells are breaking down at a faster pace than usual or that your liver isn’t breaking down waste properly and clearing the bilirubin from your blood.

3.    Kidney Panel
The blood work kidneys within the CMP bloodwork includes several tests that can be measured also in urine. BUN is an acronym for blood urea nitrogen (in comparison to urea in your urine (your pee), so a BUN tells you what the urea level in your blood is). Urea nitrogen is a normal waste product that your body creates after you eat. Your liver breaks down the proteins in your food and urea nitrogen is released as part of this process. Then, your liver releases it into the blood, and from your blood, it eventually ends up in your kidneys. When your kidneys are healthy, they remove the BUN out of your body through your urine, leaving a small amount of it in the blood. When BUN levels go up, it’s a sign that your kidneys are not functioning well.

Creatinine is a waste product from the normal breakdown of your muscle tissue. At the time your body makes it, it's immediately filtered through your kidneys and flushed out through your urine. Creatinine clearance rate shows your kidneys' ability to handle creatinine. What is a GFR blood test? The Creatinine clearance rate helps to estimate how you’re your blood is moving through your kidneys and is called the glomerular filtration rate or GFR. The entire blood in your body flows through your kidneys hundreds of times each day. Your kidneys filter your blood by pushing the liquid part of it through tiny filters called nephrons and then reabsorb most of the fluid back into the blood. Fluid and waste products that the kidneys don't reabsorb are expelled out of your body in your urine. The glomeruli are tiny bundles of blood vessels inside nephrons and are part of this filtration system. Measuring the creatinine levels in your blood check how well your kidney works and checking the creatinine level clearance or GFR shows your kidneys' ability to filter your blood. eGFR stands for estimated GFR and is calculated based on your creatinine level in your serum (the fluid and solute component of blood, which does not play a role in clotting) and factors like age, race, and gender. The higher your eGFR number, the better your kidneys are working; low results may be a sign of kidney disease.  The eGFR normal levels range for African Americans and non-African Americans are different.

Additional calculated factors are revealed from the comprehensive metabolic panel, BUN/Creatinine Ratio and A/G Ratio (e.g., albumin/total globulins.) High BUN-to-creatinine ratios occur with sudden (acute) kidney problems, which may be caused by shock or severe dehydration. A very high BUN-to-creatinine ratio may be caused by bleeding in the digestive tract or respiratory tract. High levels of immunoglobulins can be an indicator for both viral and bacterial infections, inflammatory and immune disorders, and cancer. The A/G ratio provides information about the amount of albumin you have compared with the amount of your globulins. This comparison can be a sign of a liver or kidney disease and the reason it is part of the comprehensive metabolic panel.

What tests are not included in the CMP panel?
The gamma-glutamyl transpeptidase or GGT blood test measures the level of the GGT enzyme in your blood. GGT is concentrated mainly in the liver, but it’s also present in the gallbladder, pancreas, spleen, and kidneys. It is involved with several metabolic processes and increased levels are usually found when liver disease is present. GGT on blood test is a more sensitive indicator of liver pathology than ALT and AST in detecting obstructive jaundice, cholangitis, and cholecystitis. In cases of such diseases, increased levels of GGT can be found earlier and last longer compared with ALT and AST. The GGT blood test is also used to check for alcohol problems and to predict the presence of non-alcoholic fatty liver disease (excess fat in liver cells due to an unhealthy diet and lifestyle.) and liver cancer¹. So, in a sense, GGT blood test for alcohol and non-alcoholic fatty liver disease is a deep dive into liver damage and would be ordered as part of a separate liver panel or as a result of suspected liver disease as flagged by the comprehensive metabolic panel (CMP) test.

The kidney panel in a CBP is based only on blood samples. Urinalysis and albumin/creatinine ratio or ACR urine test are additional tests that measure kidney functions, but these tests are based on urine samples and therefore are not part of CBP blood test.

Conclusion
Your blood can tell you a lot about your metabolic balance and your liver and kidney function. This blog summarizes what tests are in a comprehensive metabolic panel. A CMP bloodwork is a great screening start. It is very broad and only very few tests are missing but can be added later if your results show some abnormal levels. In case you missed your last physical exam, do not want to see your doctor, or do not have insurance, a CMP blood test is a great way to be proactive about your health and make sure your liver and kidneys are in good condition.    

Do you have now the confidence to order a CMP blood test online?

1.    Seung Wook Hong, Hyun Jung Lee , Kyungdo Han, Jung Min Moon, Seona Park, Hosim Soh, Eun Ae Kang, Jaeyoung Chun, Jong Pil Im, Joo Sung Kim, Risk of gastrointestinal cancer in patients with an elevated level of gamma-glutamyltransferase: A nationwide population-based study, PLOS ONE February 5, 2021 https://doi.org/10.1371/journal.pone.0245052