Understanding Blood Test - CBC, CMP, Lipid
In many reports the initial list of items under the “Test Name” column show the results of the CBC, or complete blood count. The CBC focuses on the health of the three types of blood cells—red blood cells, white blood cells, and platelets—by measuring their amounts, size, and volume, plus a few other things. It’s a broad screening tool that helps your doctor identify infections and allergies, or diagnose potential diseases and conditions such as anemia and leukemia. Items that are commonly measured in the CBC include:
White blood cell (WBC): Often the first CBC test shown is the White blood cell count. White blood cells, also called leukocytes, are a major component of the body’s immune system. Your body produces more WBCs when you have an infection or allergic reaction. There are five major types of WBCs (covered below), but many lab reports list the test results for each of these at the bottom of the CBC results.
Red blood cell (RBC): Red blood cells often appear next on the report. RBCs deliver oxygen to tissues throughout the body. High RBC counts can be the result of dehydration, kidney problems, or a heart condition. Low RBC counts can indicate anemia, nutritional deficiency, bone marrow damage, or kidney problems. Smokers, grab your gum/carrot sticks/nicotine patches because here’s another reason to quit: Smoking can significantly damage your RBCs.
Hemoglobin, hematocrit, mean corpuscular value (MCV), mean corpuscular hemoglobin (MCH): These test results often appear under the RBC section because they further examine the health and function of your red blood cells. Hemoglobin is the protein in red blood cells that carries oxygen. It’s measured to help determine if your organs and tissues are receiving enough O2. Hematocrit results show the volume of blood taken up by red blood cells, which helps determine if you have too high or too low an RBC count. Blood cells are often referred to as corpuscles, so the mean corpuscular value measures the average size of red blood cells. A vitamin B12 deficiency or anemia may be indicated by abnormal-size RBCs. Mean corpuscular hemoglobin measures the average amount of hemoglobin inside red blood cells (sadly, for would-be Jedi it does not measure your midi chlorians), and it’s often evaluated in association with the mean corpuscular hemoglobin concentration (MCHC), which measures the average percentage of hemoglobin in the red blood cells.
Platelets and mean platelet value (MPV): These two tests usually appear next. Platelets are fragments of blood cells. They help wounds heal and prevent excessive bleeding by forming clots. High platelet count can indicate risk for excessive bleeding, while a low count may show a risk for blood clots. The mean platelet value test measures the average amount of platelets and can reveal subtle disorders when platelet counts are normal.
Basophils, eosinophils, neutrophils, lymphocytes, and monocytes: Oddly, the results for the five types of white blood cells—basophils, eosinophils, neutrophils, lymphocytes, and monocytes—often appear below the list of red blood cell results. The amounts and the health of these cells are helpful in identifying infections and allergies. For example, neutrophils are like the EMT of your blood; they’re a type of immune cell that are among the first to arrive at the site of an infection. And basophils are a type of immune cell that has small particles with enzymes that are released during allergic reactions and asthma.
Comprehensive Metabolic Panel (CMP)
The word "metabolism" makes people think of one thing: the number on the scale (and maybe dozens of diet books with the words “mega” or “blast” shouting in all caps), but this group of tests provides a much broader picture of the body’s chemical balance and metabolism. First, to clarify, “metabolism” refers to all the physical and chemical processes in the body that convert or use energy (breathing, controlling body temp, etc.). The CMP also provides information about the body’s electrolytes, which are minerals in your blood that affect the amount of water in your body, the acidity of your blood, and muscle function. Common electrolytes tested for the CMP include calcium, chloride, magnesium, phosphorous, potassium, and sodium.
In addition, the CMP often measures substances and chemicals such as bilirubin, albumin, and creatinine. Bilirubin is formed when hemoglobin breaks down. It’s found in bile and blood, and too much of it could indicate jaundice. Albumin, the main protein in blood plasma, is the clear, yellowish fluid part of the blood that carries blood cells. Low levels of albumin can indicate malnutrition, inflammation, and liver and kidney diseases. Last but not least, creatinine is a chemical waste product of creatine, which is used to supply energy to muscles. Since it can assist in crushing your weight lifting routine, creatine is a popular supplement (hey, we all want tickets to the gun show), but creatinine is removed from the body by the kidneys, so elevated levels could indicate poor kidney function.
Another part of the CMP is often the fasting glucose test, which requires that you don’t eat for at least eight hours beforehand. Glucose is the body’s main source of energy; it’s a simple sugar the body manufactures from carbohydrates, so that stack o’ pancakes could affect the test’s outcome. (Tip: Schedule your bloodwork for first thing in the morning if you can to avoid moments of hunger rage, which is a legit problem.) Abnormal levels of glucose can be a sign of diabetes.
The lipid panel is a collection of tests that measures two types of fat in the blood—cholesterol and triglycerides. Triglycerides are one of the major forms of fat produced in the liver. If you’re wondering what affects triglyceride levels, line up the usual dietary suspects: sugar, fat, and alcohol. But triglyceride levels can also be high because of thyroid or liver disease and genetic conditions. High levels of triglycerides are related to a higher risk of heart and blood vessel disease.
There are two types of cholesterol, HDL and LDL. HDL stands for high-density lipoprotein, which is a fat that takes extra cholesterol from the blood to the liver for removal. It’s often referred to as the "good" cholesterol, as high levels of HDL cholesterol are desirable and linked to a lower risk of cardiovascular disease. LDL stands for low-density lipoprotein, which is a fat that transports cholesterol to parts of the body in need of cell repair. But it also deposits the fat on the inside of artery walls, so it’s often called the "bad" cholesterol. High levels of LDL cholesterol are linked to an increased risk of heart and blood vessel disease, including coronary artery disease. Maintaining a healthy number of triglycerides and the right balance between good and bad cholesterol are essential for a heart-healthy lifestyle.
Often your blood work results are sent to you in the mail, and unless your doctor is concerned about particular results that fall out of range, the report will likely be accompanied by a pro-forma letter that says, in effect, “Well done, keep up the good work!” Sure you can accept this at face-value. But being an informed patient is an important part of developing a strong doctor-patient relationship. With your newly acquired understanding of many of the terms and objectives of your blood test, you can become a more active participant in your health care and a better custodian of your body. more