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Ask the DocDr. Davis Smith answers questions submitted by our readers. |
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Q: Why can’t just one vial of blood be taken for different tests? It seems like a small amount would go a long way.
-Kurt P., Moorpark College
A: Kurt,
Most laboratory tests are now conducted by machine and many have mutually exclusive requirements for preparation and handling. The more tests your health care provider orders, the more vials of blood will need to be drawn. Let’s look at the parts of this in more detail.
Blood Components
Some lab tests use whole blood, just as it comes out of your vein, while some use serum-the clear, a-cellular component of blood that remains after a blood sample has been allowed to clot, then spun in a centrifuge. Additives in the vials used to collect your blood facilitate the preservation and preparation of the blood elements needed for each type of test.
Preservation
Sometimes preservatives are added to blood to protect certain components for testing. If all of the blood is collected in the same vial, it isn’t usable for tests where this isn’t required. Also, some tests require a frozen specimen.
Internal Validation
Certain results, especially those that are very abnormal, are typically re-run. Sufficient blood is necessary to conduct the tests without asking you to offer up your arm again.
Follow-up Testing
Some tests are done in a staged manner. For example, the initial process used to test for Human Immunodeficiency Virus (HIV) is usually what’s called an enzyme-linked immunoassay (ELISA). If the results are positive, a second type of test (called the Western Blot) is done for confirmation and to obtain further data.
Your Experience
How could this play out for you? During an annual physical exam I might order what’s called a Comprehensive Metabolic Panel, or CMP. This set of tests looks at:
I usually also order a Lipid Profile to measure blood cholesterol levels. This test can be run from the same vial of blood as the CMP. (You may be asked to fast prior to these tests as glucose and cholesterol metabolism can be assessed more accurately if you haven’t eaten.)
I often also order a Complete Blood Count with Differential (CBCD). This looks at:
The CBCD requires blood that has not clotted or had its serum separated-the opposite of what’s needed for the CMP.
The good news for your arms is that the tubes used for blood draws hold only a small amount of blood: 4-5 milliliters (about a teaspoon). For comparison, if you donate blood about a pint is collected, and that’s 100 times as much.
Dr. Smith would like to thank Dr. Barry Jacobs, chief of pathology and laboratory medicine at the Hospital of Central Connecticut, in New Britain, for his contributions to this answer.
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September 26th is RAINN Day, an annual campaign to raise awareness of sexual assault and recovery resources for college students.
Nut butters are tasty, versatile sources of protein and healthy fats. Here are some favorite ways to eat them.
Celery
I like to eat peanut butter with celery. Ants on a log minus the ants!
-Amanda C., Towson University
Jam
The classic way, with jam.
-Christina L., New Jersey Institute of Technology
Apples
I like to cut an apple into slices and dip it in peanut butter. You get the nutrients from the apple and the protein from the peanut butter.
-Nicholas C., Iowa Western Community College
Any Way!
That's like asking me how I like air. Any way I can get it!
-Alijah M., California State University, Monterey Bay
Did You Know?
People who regularly include nuts or peanut butter in their diets are less likely to develop heart disease, type 2 diabetes, and other chronic health conditions than those who rarely eat nuts.
Peanut butter has the enviable combination of fiber and protein that fills you up and keeps you feeling full longer.
Peanut butter is full of heart-healthy monounsaturated fat.
Oreos®
This is so difficult! I am a peanut butter fanatic and will literally put it on EVERYTHING?sandwiches, on apples, with Nutella®, on bananas. But my favorite way has got to be peanut butter on Oreos®. Yum!
-Christina A., The College of New Jersey
An Everything Bagel
With bacon and bananas on an everything bagel?Elvis style!
-Sarah M., CAST: Center for Applied Special Technology
Granola and Honey
With granola and honey all mixed together to make a sweet and crunchy treat. Helps take care of any cravings for something sweet.
-Marshé M., Spelman College
Did You Know?
Nut butters are rich in essential fatty acids. Try using them to replace butter or margarine on bread or toast!
Nut butters are easy to store without refrigeration and can be used with most foods as a dip or spread.
A Spoon
On a spoon, right out of the jar!
-Karen L., Indiana University
Nutella®
Always with Nutella®. If it's not with Nutella®, it's just not the same.
-Amanda S., University of Windsor
Cheerios®
I like to pair peanut butter with a bowl of cereal. It goes well with any kind of cereal, but my favorite cereal to pair it with is Cheerios®.
-Ofeila E., University of Arkansas, Fort Smith
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