What is a Coccidioides Precipitin Test?
Coccidioides precipitin is a laboratory blood test. It is ordered when a doctor suspects that a patient may have coccidioidomycosis (AKA “valley fever”), an infection caused by the fungus Coccidioides immitis. The test is also known as the coccidioidomycosis antibody test or the test for precipitating antibodies.
Fungi are a type of organism that lives in air, soil, water, plants, and sometimes in the human body. Not all fungi are harmful. If the body determines a foreign microorganism to be harmful, the body’s immune system makes specific antibodies (immunoglobulin proteins) to fight it. The coccidioides precipitin test looks for antibodies to Coccidioides immitis in the blood.
A closely related test is the coccidioides complement fixation test. This test looks for antibodies to Coccidioides immitis in the blood serum. Serum is the clear liquid part of the blood, which is separated out from the blood plasma.
A coccidioides precipitin test is also known as the coccidioides antibody test or the coccidioides immitis complement fixation assay test.
What Causes Coccidioidomyosis?
Coccidioidomycosis is also known as valley fever. The fungus that causes this condition grows in the dust and soil in southwestern United States, Mexico, and South America. It is a common cause of pneumonia in these areas.
You can catch it by breathing the spores of Coccidioides immitis into your lungs.
People most at risk of becoming ill from coccidioidomycosis:
- have a weak immune system
- have a heart or lung condition
- are of Native American, African American, or Filipino descent
- are pregnant in their third trimester
People with weak immune systems are especially vulnerable to fungal infections. This includes those with AIDS, HIV, diabetes, cancer, or people who take immunosuppressant treatments. Immunosuppressant treatments include chemotherapy, transplant antirejection drugs, and glucocorticoid medications.
Symptoms that May Lead Your Doctor to Order a Coccidioides Precipitin
The symptoms of coccidioidomycosis can vary. For example, one patient may have no symptoms, while others may experience cold, flu, or pneumonia symptoms, or have signs of a serious systemic infection.
The common symptoms of coccidioidomycosis include:
- swelling in the ankles, legs, and feet
- chest pain, sometimes severe
- bloody cough
- night sweats
- muscle aches and joint stiffness
- loss of appetite
- red, painful lumps on lower legs (erythema nodosum)
In its advanced form (disseminated coccidioidomycosis), the infection can spread from the lungs via the bloodstream and affect the bones, skin, central nervous system, lymph nodes, and other organs. People who have this systemic disease can become very sick.
Symptoms of disseminated coccidioidomycosis can include:
- skin lesions
- bone and joint infections
- chronic pneumonia
- enlarged lymph nodes
- neck stiffness
- mental changes
- hypersensitivity to light
- weight loss
Procedure: How a Blood Sample Is Taken
Your doctor, a nurse, or a specialist will draw blood from a vein, usually on the underside of the elbow. The site is first cleaned with a germ-killing antiseptic. Then an elastic band is wrapped around the arm above the vein. This causes the vein to swell with blood.
The healthcare provider gently inserts a needle syringe into the vein. Blood collects in the syringe tube. When the tube is full, they remove the needle.
The elastic band is then removed, and the needle puncture site is covered with sterile gauze to stop bleeding.
How to Prepare for Your Blood Test
Your doctor may ask you to fast before the blood test. If not, no other preparation is needed.
Risks of Taking the Blood Test
Complications from having blood drawn are very rare. Uncommon risks of blood tests are excessive bleeding, fainting (or feeling lightheaded), hematoma (blood pooling under the skin), and infection at the puncture site.
Understanding Your Test Results
An abnormal result means that Coccidioides immitis antibodies were found in your blood (or, in the case of coccidioides complement fixation, your blood serum). If antibodies are found, other tests on your sputum (phlegm) or blood may be ordered to confirm whether you have an infection.
A normal result means that Coccidioides immitis antibodies were not found in your blood. If you have been sick only a short time, fungal antibodies may not show up on the first test. It takes time for the immune system to produce enough antibodies to be visible. Your doctor may order repeated precipitin tests over several weeks to confirm the findings.
Results of Coccidioides Complement Fixation
The coccidioides complement fixation test is not completely specific. For example, if the patient has an infection caused by another type of fungus, such as Histoplasma capsulatum, or Blastomyces dermatitidis, the test could show positive for the Coccidioides immitis, even though it is not present in the blood sample. Additionally, it is possible for the test to come back normal in people who have lung masses caused by coccidioidomycosis. If your doctor has reason to suspect this condition is present, further tests will be needed. It takes time for the immune system to produce enough antibodies to be detected by the test. Your doctor may order additional complement fixation tests over several weeks to rule out this cause of infection.
If there is doubt about the results of your test, your doctor will work with you to make an accurate diagnosis. Other fungus tests may be ordered.
Outlook and Follow Up After Your Test
If you have a healthy immune system, you may get well without treatment.
However, in people with weak immune systems, fungal infections can be dangerous. Antifungal medications may need to be continued for three months to several years. During treatment, any immunosuppressant drugs you are taking should be stepped down or discontinued to help your body fight the infection.
According to the U.S. Centers for Disease Control and Prevention, approximately 60 percent of coccidioidomycosis cases have no symptoms. Patients who do have symptoms feel like they have the flu, and the disease is self-limiting, which means that it goes away on its own. Approximately 1 percent of patients with coccidioidomycosis go on to develop disseminated coccidioidomycosis (CDC, 2009). When the disease progresses to disseminated coccidioidomycosis, it is often fatal, although that varies a great deal depending on the patient’s age and overall health. According to the Center for Food Security and Public Health at Iowa State University, about 30 to 50 percent of patients with untreated disseminated disease progress to meningitis, an infection of the brain and spinal cord, and that is typically fatal (ISU, 2009).
A chronic form of this disease can develop up to 20 years after the first infection occurs. This can cause lung abscesses to form and rupture, releasing pus into the pleural space between the ribs and the lungs.