The Wonders of Blood

These dreaded words—“we’ll need to do a blood test.”—send many patients into a panic. Doctors, on the other hand, love blood tests. Not in a vampiristic way, but in a scientific way, because many mysteries of the body are revealed by examining this essential red fluid. Blood analysis is one of the most helpful tools in modern medicine.

Blood is the great delivery system of the body. It is a mixture of cells and a fluid called plasma. Red blood cells, which derive their color from their iron content, absorb and bind oxygen as they pass through the lungs and later release it into tissues that need it. They then bring carbon dioxide from those tissues back to the lungs to be exhaled.

White cells are delivered to the areas of the body that have been invaded by irritants or infections and help limit the intrusion. Yet another type of cell, platelets, are deposited by the blood into the areas of leakage, where clotting is needed. Platelets pile up one upon another, like plates in the sink, to plug up the breach.

Plasma is what is left of blood if all of the cells are removed. Plasma is replete with nutrients, such as protein, glucose, and vitamins, that are indispensable to the function of each and every cell. It is the conduit for hormone delivery, carrying thyroid, adrenal, and reproductive hormones from the parent gland to the target organs. Life-sustaining minerals—such as potassium, sodium, and chloride—are transported via plasma to assure proper levels in every body system.

Blood was recognized as a critical body component in ancient times, but it wasn’t until 1628 that the father of cardiology, William Harvey, discovered that it was pumped by the heart and circulated throughout the body. Within 50 years, the first blood transfusion was attempted. But it was not until 1892 that the great statesman of modern medicine, Sir William Osler, described the utility of routine blood testing. Initially, these examinations were extremely basic and noted only the amount of cells, but within 10 years a way to “type” the blood and improved the success of transfusions developed. There has been a continual stream of developments in the field of blood analysis since then, with an ever-growing number of ways the science of blood can improve health.

The innumerably helpful effects of blood tests can be divided into four main categories: (1) improving the safety of a blood transfusion, (2) diagnosing disease, (3) monitoring the safety and efficacy of medical treatment, and (4) detecting the risk of future disease.

While most of us will be lucky enough to avoid transfusion during our lifetimes, we all potentially benefit from the improved ability of blood banks to screen and type their supply. Routine analysis now dramatically reduces the risk of adverse reaction during the transfusion and of contracting blood-borne diseases like syphilis, hepatitis, and HIV.

Since they were first developed, blood tests have been invaluable tools in disease diagnosis. Initially, by evaluating blood counts, physicians were able to identify overwhelming infection (by high white counts) and anemia (by low red cell counts). Shortly after, clotting disorders such as hemophilia were able to be clearly detected. Then excessive sugar in the plasma was found to reveal diabetes sooner and more reliably than the traditional urine tests. Now the brief discomfort of venipuncture can help your doctor detect thousands of conditions ranging from Lyme disease to thyroid imbalance. Heart attacks, liver and kidney problems, and vitamin deficiencies can be recognized definitively, thus allowing essential therapy to be started.

Laboratory analysis is also a vital guide to guide and track medical treatment. Drugs used to treat disorders, such as epilepsy and rheumatoid arthritis, are toxic if administered in excess. Blood levels help practitioners determine the proper does. Blood thinner treatment with the medication Coumadin (warfarin), is rendered incalculably safer by an exam called an INR. It can be performed with a drop of blood from a finger stick. Cholesterol medication protocols are guided by blood examination to ensure that this blood fat is properly reduced without straining the liver. DNA analysis has become one of the most exciting frontiers in medical science.

So blood, that vital fluid without which we cannot live, can reveal much about ourselves, including our present and future health. Don’t begrudge your doctor a few milliliters to ensure your wellness. And if you fear you have or may have an illness, don’t hesitate to talk to your doctor about getting a blood test. It could save your life.

Patrice Thornton, MD, is a family medicine physician at SVMC Northshire Campus in Manchester, VT, which is part of Southwestern Vermont Medical Center in Bennington. She is accepting new patients.