Serology

How the Test is Performed:
Adult or child:
Blood is drawn from a vein ( venipuncture ), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (fill with blood). A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the tourniquet is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding .

Infant or young child:
The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.

The blood is then analyzed in a laboratory. Serology refers to the study of serum for its antibody content. Certain microorganisms stimulate the body to produce these antibodies during an active infection. In the laboratory, the antibodies react with antigens in specific ways that can be used to confirm the identity of the specific microorganism. There are several serology techniques that can be used depending on the suspected antibodies. Serology techniques include agglutination, precipitation, complement-fixation, fluorescent antibodies, and others.

How to Prepare:
Adults:
There is no special preparation.

Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:



How it Feels:
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing .

Risks:

  • excessive bleeding
  • fainting or feeling lightheaded
  • hematoma (blood accumulating under the skin)
  • infection (a slight risk any time the skin is broken)
  • multiple punctures to locate veins



Why this Test is Performed:
A serology may be performed when an infection is suspected.

Normal Values:
No antibodies are detected. However, during the first few days to weeks of exposure to an antigen , there may be slight antibody production. As the disease progresses, more antibodies will be present. If a disease is suspected, the test may need to be repeated 10 days to 2 weeks after the first test.

Abnormal Results:
If antibodies are detected, there has been exposure to an antigen . Some of the different diseases that can be detected include:

Additional conditions under which the test may be performed:



Cost:
Information not available.

Special Considerations:
A serology test can determine if a patient has ever been exposed to a particular antigen , but this does not necessarily indicate a current infection.

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.


Legionnaires disease was first described in 1976 after and outbreak of fatal pneumonia at a Legionnaires convention. The newly described organism which caused the disease was named Legionella pneumophila, shown in this picture. (Courtesy of the Centers for Disease Control.)



This microscopic film shows a fluorescent stain of Candida. Candida is a yeast (fungus) that causes mild disease, but in immunocompromised individuals it may cause life-threatening illness. (Courtesy of the Centers for Disease Control.)



This child has a large rash caused by Candidiasis, affecting the skin around the mouth. There are also other lesions that aren't connected to the large lesion, called "satellite lesions".



Candida is a yeast-like organism that causes diaper rash and thrush (oral candidiasis) in infants. Occasionally, skin other than the diaper area may be involved. This photograph shows multiple small candidal infections on the arm.



A paronychia is an infection around the nail. Many organisms can cause a paronychia. This particular case is caused by the yeast-like organism Candida. Note the inflammation (red, swollen area) at the base of the nail and the changes that are apparent in the nail itself.



Persistently moist skin produces conditions conducive to the growth of Candida (a yeast-like organism). This is a Candida infection in the armpit (axilla).



Candida grows best in areas of skin that are very moist. Folds in the skin, such as the crease of the buttocks, may allow this organism to grow.