Most Common Blood Tests in Phlebotomy

Blood tests are done for a number of reasons—help diagnose a health problem, assess the condition of certain organs, screen a patient for genetic conditions, run parental test and many others. A phlebotomist is usually responsible for collecting blood specimen and, once in a while carries out the blood test or transport the sample drawn.

Collection of blood can be done in many ways, but venipuncture is the most common procedure. Specimen is drawn from a vein inside the elbow or at the back of the wrist. A tourniquet causes venous blood to occlude and makes the vein more prominent and easy to spot. The entire process starts with disinfecting the puncture site, followed by the standard venipuncture procedure.

The process varies, depending on the sample needed for blood testing. There are instances when several samples have to be taken over a certain period of time, just a small amount, or specifically from an artery in the wrist.

Common Blood Tests

Blood typing

This is probably one of the simplest tests done, but just as important. It is usually performed before blood donation or transfusion to check for compatibility. Failure to do so could lead to potential fatal complications. This is also carried out during pregnancy if there is a risk that the unborn child may have a different blood type than the mother, which raises the possibility of rhesus disease (http://www.nlm.nih.gov/medlineplus/ency/article/001600.htm), a condition where a mother’s immune system can attack the red blood cells of the baby.

Full blood count (FBC)

An FBC does not usually provide a definitive diagnosis about a particular health condition, but it is sure to give doctors or pathologists a clue as to what is causing a particular problem to occur, including the following:

1. Low Hemoglobin

This usually indicates anemia, a condition when a patient doesn’t have enough healthy red blood cells to transport adequate oxygen to the rest of the body. Symptoms of anemia vary from one person to another, which make blood testing the most logical option to verify its presence. Anemia is caused by a number of things—poor diet or internal bleeding.

2. High hemoglobin

The opposite of low hemoglobin indicates a possible problem with the bone marrow or underlying lung disease. If the hemoglobin levels are above the normal values for a particular age or sex, a patient has high hemoglobin.

Widely accepted normal ranges are the following:

• Birth: 13.5 to 24.0 g/dl (mean 16.5 g/dl)
• Age <1 month: 10.0 to 20.0 g/dl (mean 13.9 g/dl)
• Age 1-2 months: 10.0 to 18.0 g/dl (mean 11.2 g/dl)
• Age 2-6 months: 9.5 to 14.0 g/dl (mean 12.6 g/dl)
• Age 0.5 to 2 years: 10.5 to 13.5 g/dl (mean 12.0 g/dl)
• Age 2 to 6 years: 11.5 to 13.5 g/dl (mean 12.5 g/dl)
• Age 6-12 years: 11.5 to 15.5 g/dl (mean 13.5)
• Female: Age 12-18 years: 12.0 to 16.0 g/dl (mean 14.0 g/dl)

Age >18 years: 12.1 to 15.1 g/dl (mean 14.0 g/dl)

• Male:  Age 12-18 years: 13.0 to 16.0 g/dl (mean 14.5 g/dl)

Age >18 years: 13.6 to 17.7 g/dl (mean 15.5 g/dl)

3. Low white blood cell count

This type of condition is not always a cause for worry. But it can be indicative of a viral infection, bone marrow problems or cancer of the bone marrow, which is often a rare case. Since the threshold for low white blood cell count varies, common blood tests are highly recommended.

4. High white blood cell count

A microliter of blood with a count of more than 11,000 leukocytes is considered a high white blood cell count, although the threshold varies from one medical practice to another. An increase in leukocytes, disease-fighting cells, is not necessarily a disease, but could indicate other problems, including infection, inflammation, stress and, in rare cases, a sign of leukemia.

5. Low platelet count

A low platelet count may be due to a viral infection or when a person’s immune system attacks healthy tissues, most common with autoimmune conditions.

6. High platelet count

A patient with high platelet count may be suffering from inflammatory conditions, or bone marrow infection or problem. This test is often included in a complete blood count (http://labtestsonline.org/understanding/analytes/cbc/) or a panel of tests to determine overall health.

Coagulation test

This is done to measure how fast blood clots and check for possible bleeding disorders. People with hemophilia or von Willebrand disease will greatly benefit from this kind of blood test.

Erythrocyte sedimentation rate (ESR)

ESR, when used with other tests, can help confirm if a patient has an infection. What this does is measure the amount of time that the red blood cells fall to the bottom of a test tube. If it takes faster than normal, it usually indicates high levels of inflammation that is often associated with arthritis, Crohn’s disease, temporal arteritis, endocarditis and polymyalgia rheumatic.

Blood sugar levels

This is one of the common blood tests that diabetes patients must undergo to ensure their glucose levels remain normal to avoid possible complications. It is often a part of diabetes treatment. While blood glucose test can be done at home, patients with type 2 diabetes must be tested every 3 to six months in a hospital.

C-reactive protein (CRP)

This is another procedure done to test possible inflammation in the body. CRP is produced by the liver and a high level of it can spell bad news for a patient.

Blood culture

While most common blood tests are done to check for infection or other health conditions, a blood culture is done to determine traces of bacteria in a patient’s body. This is done by introducing nutrients that will encourage growth of bacteria. Two blood samples must be drawn for culturing in case of accidental contamination.

Other blood tests include blood cholesterol, electrolyte test, thyroid function test, genetic testing and screening, chromosome testing, liver function test, amylase test and many others. All these are done to find clues of possible health conditions a patient may have. Even if there are no visible symptoms, blood test should be done at least once a year.