Traditionally performed in physician offices and laboratories, blood tests are one of the useful tools that are used for diagnosing or uncovering disorders in the human body. They can detect abnormalities by measurements of many substances that when found to be very high or low may indicate a variety of diseases. 

During the diagnostic process, blood tests are one of the procedures ordered that may help to rule out other diseases and disorders. These conditions can include gynecological conditions such as cancers, sexually transmitted diseases and pregnancy.

The four main types of blood tests include hematology tests, biochemistry tests, microbiology tests and serology tests. Depending on the amount of blood required for the test, blood can be drawn from a vein puncture (venipuncture), artery puncture (arterial puncture) or skin puncture.

Blood tests can be completed in a physician’s office, laboratory or medical facility. Blood is usually drawn by a phlebotomist, who is a medical assistant trained in the procedure. It may be drawn by other healthcare professionals, such as a physician, nurse or lab technician.

Obtaining a blood sample only takes about five minutes and most patients find blood tests to be relatively painless. Some blood tests may require fasting or other preparation, however, for most blood tests, there is very little preparation beforehand, and people can generally return to their usual daily activities following testing.

A blood test uses a sample of blood to detect and measure various factors in the blood. It is important to measure these factors because abnormally high or low levels of certain elements may affect normal body function. These abnormal levels may occur when certain body organs are affected by diseases. The presence or absence of some elements in the blood also can provide information about a person’s health.

Samples of blood may be taken in one of three ways:

• Vein puncture (venipuncture). A needle is inserted directly into a vein to draw blood into one or more tubes. Blood is usually drawn from a vein in the inner arm, opposite the elbow.
  
  
• Skin puncture. Used when only a small amount of blood is needed to perform the desired blood test. The skin of the finger, earlobe or heel (in infants) is jabbed with a needle to produce a drop of blood that is then collected for testing.
  
  
• Artery puncture (arterial puncture). Used only when the blood test needs to be performed on a sample of oxygen-rich blood traveling from the heart to the body via the arteries. Blood is usually drawn from an artery in the side of a wrist.

Blood tests can be performed on different parts of the blood, including:

• Whole blood (blood that has not been separated into its many components)
  
  
• Blood plasma (the liquid part of the blood)
  
  
• Blood serum (plasma that has had the clotting agent removed)
  
  
• Blood cells (the individual red blood cells, white blood cells and platelets)

Blood tests can be used to diagnose or monitor several gynecological conditions. Such conditions include:

• Pregnancy. These tests look for the presence of human chorionic gonadotropin (HCG), also known as the “pregnancy hormone.” There are two major types:
  
  
• Quantitative blood test. Also known as a beta HCG test, it measures the exact amount of HCG in the blood and can pick up even tiny amounts of the hormone. This test is very sensitive and can accurately diagnose pregnancy in women.
  
  
• Qualitative blood test. This test reveals a simple yes or no answer as to whether a woman is pregnant.
  
  
Blood tests can reveal whether a woman is pregnant between six and eight days after ovulation. They can detect pregnancy earlier than urine tests, which are commonly used in home pregnancy kits.

Once a woman has been diagnosed as pregnant, she may receive a maternal serum testing to check for birth defects in the fetus. This test, which is typically offered to a woman between the 15th and 18th weeks of her pregnancy, can detect the presence of alpha-fetoprotein (AFP) in the blood. High levels of this substance may indicate that the fetus has a neural tube defect such as spina bifida, whereas low levels may indicate the presence of Down syndrome or other chromosome abnormalities.

Pregnant women may also receive blood testing to check for disorders related to pregnancy, such as gestational diabetes, toxoplasmosis (an infection that can be passed to the fetus) or anemia (deficiency of red blood cells, hemoglobin or total blood volume). Blood tests can reveal important information about Rh factor, a substance found on red blood cells. Rh incompatibility occurs when a woman is Rh-negative and her fetus is Rh-positive. It can cause health problems for the fetus and needs to be addressed before delivery.

Another common prenatal blood test, the rubella titer, indicates whether the patient is, like most people, immune to German measles (rubella), a rare disease. German measles contracted by a pregnant woman can cause blindness and other serious problems in the baby. Most individuals have received a vaccine – called the measles, mumps and rubella (MMR) vaccine – for this and should have immunity.


• Sexually transmitted diseases (STDs). Blood tests can be used to detect STDs such as oral or genital herpes. Three different tests – enzyme immunoassay (EIA), enzyme-linked immunosorbent assay (ELISA) and Western blot (WB) – are used to check for human immunodeficiency virus (HIV) infection. HIV is the virus that causes AIDS.
  
  
• Gynecological cancers. Blood tests can be used to reveal tumor markers, substances that include proteins, enzymes or other biochemicals that may indicate the presence of or predisposition to cancer. Some tests may be used to diagnose cancers of the uterus, ovaries and breast. Other tests may indicate the presence of a genetic abnormality, such as the BRCA gene mutation associated with breast cancer.
  
  
• Menopause. A blood test called an FSH level can be used to confirm perimenopause or menopause. Follicle-stimulating hormone (FSH) is made in the pituitary gland in the brain and circulates in the blood to stimulate the ovaries to make estrogen and progesterone during a woman’s reproductive years. Once the ovaries stop making estrogen and progesterone, the pituitary gland compensates by making more FSH. FSH levels greater than 25 to 40 are a sign of menopause.

Hundreds of blood tests are performed every day in laboratories and in people’s homes. In general, there are four main types of blood tests:

• Hematology tests
• Biochemistry tests
• Microbiology tests
• Serology tests

Hematology tests examine the blood to identify:

• The types and number of blood cells that are present (e.g., red blood cells, white blood cells and platelets)
  
  
• The appearance of the cells, especially their maturity
  
  
• The ability of the blood to form a blood clot and the speed at which clotting occurs
  
  

One of the most common blood tests is the CBC (complete blood count). This test is used to gain information about cell count and additional factors (e.g., hemoglobin) in the blood. Biochemistry tests measure the levels of normally occurring chemicals and biochemicals in the blood, both individually and in relation to other chemicals. These measurements are compared to normal ranges, and are used to determine whether blood biochemicals are in a proper and healthy balance. Biochemicals and other substances that may be studied include:

• Sodium
• Cholesterol and other fats
• Vitamins and minerals
• Hormones
• Blood gases
• Prescription drugs
• Recreational drugs
• Alcohol

Not only can biochemical tests precisely measure these substances, but they can also be used to indicate how well some organs and organ systems are functioning. For instance, when cancer spreads to the liver, it may affect the organ’s enzyme production. As a result, measuring the amount of certain enzymes in the bloodstream can indirectly reflect the progression of the disease and its effect on the liver.

Microbiology tests examine blood for the presence of infectious microscopic organisms such as:

• Bacteria
• Fungi
• Viruses (in most clinical labs a serology test is used)
• Parasites

Microbiology tests include:

• Smears, in which a small amount of blood is placed on a glass slide for examination under a microscope. Sometimes the blood smear is stained with special dyes before examination.
  
  
• Blood cultures, in which a small amount of blood is placed in a nutrient broth, incubated for days or weeks and then examined for growth of disease-causing bacteria.

Serology tests (tests performed on blood serum) can detect the presence of antibodies that are produced by white blood cells to attack microscopic organisms. They are frequently used to detect viral diseases. Most hospital laboratories do not have the equipment or specially trained personnel necessary to isolate the viruses themselves, so serology tests are done instead to identify the infecting organism by studying the antibodies produced against it.

Preparation for blood tests varies according to the requirements of each specific test. In most cases minimal preparation is necessary. The patient may need to reduce or stop certain medications and vitamins at some point prior to the test. Additionally, food intake and exercise may be temporarily restricted or suspended. Alcohol and caffeine should be avoided prior to a blood test.

On the day of the test, the procedure will be explained and patients will have the opportunity to ask questions. The medical professional will also ask questions about the patient’s medical history before the test, to determine if the patient is taking any medications that will interfere with the test’s accuracy or has any history of clotting problems.

Blood tests may be performed by a number of healthcare professionals, including physicians, nurses and medical lab technicians. In many laboratories and medical facilities, blood is drawn by a phlebotomist who is a medical laboratory assistant specially trained in collecting and handling blood.

Drawing blood for a blood test is an easy and virtually painless process for most people. If the test only requires a drop or two of blood, then a simple prick of the finger, earlobe or heel (in the case of a baby) can provide enough blood for testing.

A sterile, sharp lancet is used to prick the skin. The technician will then gently squeeze the puncture area to produce drops of blood that are collected in tiny glass tubes. Light pressure and sterile gauze are then applied to the puncture site to stop the bleeding. A bandage is usually not necessary.

If a substantial amount of blood is needed, it is usually drawn from a vein in a process called venipuncture. During venipuncture, a needle is inserted into a vein – usually at the end of the elbow or on the back of the hand. If the technician has difficulty drawing blood from the initial site, he or she may choose a different vein. The area around the puncture site is cleaned with rubbing alcohol and a wide elastic band or piece of latex tubing may be placed around the upper arm to slightly increase pressure in the vein. One end of a sterile double-ended needle that has been attached to an open-ended syringe (which contains an empty test tube) is inserted into the vein. Because the test tube contains a partial vacuum, blood flows directly from the vein through the double-ended needle and into the test tube.

The precise amount of blood to be drawn is determined by the type and number of tests scheduled. It is usually around 7 milliliters. The technician may change test tubes once or twice during a venipuncture to either allow for more blood to be collected or to change the type of tubing being used. Tubes are marked with different color tops that indicate the way in which the collected blood will be preserved:

• A lavender top indicates that the tube contains an anticoagulant, which prevents the collected blood from clotting.
  
  
• A red top indicates that the tube contains no anticoagulants, allowing serum and the blood to form a blood clot.
  
  
• A gray top indicates that the tube contains a preservative, which keeps blood sugar from breaking down in the tube.

After the necessary amount of blood is drawn, the needle is withdrawn and a small cotton ball or pad is applied with light pressure over the puncture site. After several minutes, the cotton will be discarded or replaced, and a small bandage will be placed on the puncture wound. The entire process takes less than 10 minutes.

Despite the precautions taken to avoid bruising and soreness, they do sometimes occur. Typically, this is not a cause for great concern. To minimize soreness, patients may immediately apply a warm compress to the puncture site and repeat the application every three hours until the discoloration or pain subsides.

If blood must be taken from an artery instead of a vein, it is usually drawn from a very small artery located on the inside or the top side of the wrist.

Following the withdrawal of blood in a physician’s office or laboratory, patients may resume medications and food intake according to their physician’s instructions. Immediately after the blood sample is taken, the test tubes are labeled with the date, the patient’s name and any other necessary information. In some cases, the blood test analysis may be completed on site. Otherwise, the blood sample is sent to the laboratory for testing. The length of time to receive the results depends on the urgency and type of blood test. Based on the test results, additional blood tests may be ordered.

Test results are always evaluated in relation to the “normal range” for that test. The range of values considered to be normal is the range of test results from the blood of normal, active healthy people. When a woman has a gynecological or other health problem, her blood test results may be higher or lower than normal – or “outside the normal range.” A physician who sees that a result is outside the normal range may order repeat tests to verify results or additional tests to determine the underlying causes behind the abnormality.

Normal ranges for some tests may vary between laboratories, especially with facilities that use machines to perform blood tests and those who perform blood tests by hand. Frequently, results of a patient’s blood test are compared to another “known” blood sample taken from a healthy individual that is run at the same time and is designated as the “normal control.” When the “normal control” sample falls within the normal range, or reaches a specific “known” measurement, the laboratory results confirm that the blood test has been carried out accurately.

There are very few risks or side effects reported with blood tests. Occasionally, bruising is reported at the injection site. This can be minimized by keeping direct pressure on the spot for several minutes after the needle has been removed.

In rare situations, the vein used to obtain the sample may become inflamed. Applying warm compresses to the spot several times daily can help reduce the swelling. Also rare are infections caused by nonsterile conditions.

Individuals with bleeding disorders or who are taking anticoagulants (including aspirin) may have problems with continued bleeding. Those who experience these side effects should consult with their physician.

When drawing blood, only sterilized, single-use needles are used by the healthcare professional. In addition, they are trained in standard precautions to eliminate any risk of infection for themselves or the patients. In almost all instances, the healthcare professional wears disposable gloves when drawing or handling blood. Infections from nonsterile conditions are rare with blood tests.

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor or healthcare professional the following questions related to blood tests:

1. What type of blood test will I need?
   
   
2. Which gynecological conditions can be diagnosed through a blood test?
   
   
3. Are there any risks associated with this blood test?
   
   
4. Does the test require any special preparation?
   
   
5. Where should I have the test done?
   
   
6. How much blood will be taken?
   
   
7. Will the blood test affect my pregnancy?
   
   
8. When can I expect the results and how will I receive them?
   
   
9. Will I need to have the blood test repeated?
   
   
10. Will I need any additional tests?
    
    
11. What is the next step if the test results are abnormal?