What are the most common blood lab tests requested for physical examinations and what is the function of each?
1. Complete Blood Count (CBC) with Differential
Complete Blood Count with Differential is one of the most commonly ordered tests for routine check-ups and/or physicals. This test measures the levels of red blood cells, white blood cells, platelet levels, hemoglobin and hematocrit. It is useful as a screening test because it provides information about a wide variety of bodily functions and it can be used to aid in diagnosing and treating a large number conditions.
Red blood cells carry oxygen. A percentage of these cells contain hemoglobin, which has the capacity to combine with iron. It's the iron-hemoglobin molecular structure that helps carry oxygen-rich blood from the lungs to your tissues. In return, it delivers carbon dioxide back to the lungs to be expelled. A CBC with Differential that shows low red blood cell levels can indicate anemia.
White blood cells (also called leukocytes or immune cells) are a part of the immune system and help defend your body against infectious diseases and foreign materials. Elevated white blood cells on a CBC blood test may mean that the body is responding to an infection of some kind. If your CBC shows low levels, this can indicate that your immune system is not functioning normally.
Platelets, which are produced in the bone barrow, are checked on a Complete Blood Count with Differential. Platelets help stop bleeding from injury by creating clots. Low platelet levels may indicate that you are more susceptible to bleeding. High platelet levels could mean that you have an increased risk of internal clots.
A Complete Blood Count with Differential also includes hematocrit, which is a measure of the density of red blood cells in your blood. A low hematocrit level can mean problems like anemia, leukemia, or other bloodstream disorders. High hematocrit levels can mean that you're dehydrated.
2. Comprehensive Metabolic Panel
The Comprehensive Metabolic Panel (CMP) is a group of blood tests that provides information about liver and kidney function. It measures electrolytes, acid/base balance, blood protein, and blood sugar levels. Test results are listed next to normal values for each test (normal values are usually printed in parenthesis). Out-of-range results can indicate potential health problems.
The CMP includes:
- Albumin
- Total Protein
- Sodium
- Potassium
- CO2 (carbon dioxide, bicarbonate)
- Chloride
- BUN (blood urea nitrogen)
- Creatinine
- ALP (alkaline phosphatase)
- ALT (alanine amino transferase, also called SGPT)
- AST (aspartate amino transferase, also called SGOT)
- Bilirubin
3. Lipid Profile
The Lipid Profile is a blood test that measures cholesterol in your body. Cholesterol is a waxy, fat-like substance found in certain foods and in your body's cells. Your body needs a small amount of cholesterol to function normally. When too much cholesterol is present, it can harden in the arteries and turn into plaque, which restricts the flow of blood to the heart and brain. Over time, this buildup causes hardening of the arteries (atherosclerosis), and heart disease.
The Lipid Profile is collected after a 9-12 hour fast – no liquids, food, or pills should be consumed during this period. You may drink water and take prescription medications unless directed otherwise by your physician.
According to The American Heart Association, all adults age 20 or older should have a fasting lipid profile, which measures the 4 levels listed below:
Total Cholesterol
The total cholesterol measure represents an overall view of the blood lipid levels. A total cholesterol level of 200 or more indicates an increased risk for heart disease.
LDL Cholesterol
LDL is called "bad cholesterol" because it tends to stick in the arteries, forming hard plaques which lead to atherosclerosis. This lab value is usually categorized as optimal, borderline, high, and very high. Lower LDL cholesterol means a lower risk of heart attack and stroke. It's a better gauge of risk than your total blood cholesterol.
HDL Cholesterol
HDL is called "good cholesterol” because it helps to remove LDL (bad) cholesterol and keeps the inner walls of blood vessels healthy. HDL cholesterol is protective, and it is good to have higher levels. A low HDL count increases the risk for heart disease. Smoking cessation, maintaining a healthy weight, exercising regularly, eating healthy fats, and limiting alcohol intake can help boost HDL levels.
Triglycerides
Elevated triglycerides are usually related to lifestyle: obesity or being overweight, physical inactivity, tobacco use, excess alcohol consumption, and poor diet. Elevated triglyceride counts can also be associated with chronic conditions like hypothyroidism or diabetes, and can be noted as a side-effect of certain medications.
Elevated cholesterol levels generally do not produce any visible symptoms, but can result in the development of serious conditions like hypertension, stroke, and heart attacks. Keep in mind that your cholesterol level is only one aspect of your risk for heart disease; other risk factors such as age, family history, smoking and high blood pressure should also be taken into account.
This information was prepared by Molly Haynes, DNP, APRN, FNP-C, BarnesCare nurse practitioner.