Colorado Tick Fever Virus IgG and IgM Antibodies Blood Test
This blood test detects antibodies to Colorado tick fever virus, helping diagnose recent or past infection transmitted by ticks. The panel measures IgM antibodies, which usually appear within one to two weeks after infection and suggest a recent or active illness, along with IgG antibodies, which develop later and can stay in your blood for years as a sign of past exposure or immunity. Your doctor may order this test if you have symptoms such as sudden high fever, severe headache, muscle aches, or fatigue after a tick bite or time spent in areas of the western United States where tick-borne disease is common.
{"Detects IgM antibodies indicating recent infection (within past few weeks)","Detects IgG antibodies indicating past infection or immunity","Sample is collected from a blood draw (serum)","Results help your doctor confirm or rule out Colorado tick fever","Positive IgM usually means active or recent infection requiring treatment"}
Key facts at a glance
- LOINC
- 57774-2
- Short code
- CTF IgG/IgM
- Synonyms
- CTFV IgG+IgM Pnl Titr Ser
- Category
- cardiac
- Sample
- serum
- Container
- Serum separator tube (SST) or red top tube
- Units
- N/A
- Ref low
- 64
- Ref high
- 64
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- Enzyme-linked immunosorbent assay (ELISA) or Immunofluorescence assay (IFA)
- CPT
- 86635
- SNOMED
- 186747009
- Specimen volume
- 1-2 mL of serum
- Stability
- Room temperature: 8 hours; Refrigerated (2-8°C): 72 hours; Frozen (-20°C or below): 30 days
- Hemolysis max
- 50
- Lipemia max
- 100
- Icterus max
- 20
- TAT
- 48–168 hours
- Order
- routine
What is this test?
The Colorado tick fever virus IgG and IgM panel is a blood test that looks for specific antibodies your immune system produces in response to Colorado tick fever virus infection. IgM antibodies typically appear first (within 1-2 weeks of infection) and indicate a recent or active infection. IgG antibodies develop later and can remain in your blood for years, indicating past infection or immunity.
Why is this test ordered?
Your doctor may order this test if you have symptoms of Colorado tick fever, especially if you have been bitten by a tick or have recently spent time in areas where tick-borne diseases are common (typically the western United States). Symptoms of Colorado tick fever include sudden high fever, severe headache, muscle aches, fatigue, and sometimes a rash. This test helps confirm whether your symptoms are caused by Colorado tick fever virus or another condition.
How is the test performed?
A healthcare professional will draw a small sample of blood from a vein in your arm. This blood sample will be sent to a laboratory where technicians will analyze it for the presence of IgG and IgM antibodies against Colorado tick fever virus. The test is qualitative, meaning it shows whether antibodies are present (positive) or absent (negative), rather than measuring a specific amount.
What do the results mean?
Results are reported as positive or negative for IgG and IgM antibodies. A positive IgM result with negative IgG suggests a recent (acute) infection. Positive IgG with negative IgM suggests a past infection or immunity. Positive results for both IgG and IgM may indicate an ongoing or recent infection. Your doctor will interpret these results together with your symptoms and medical history to make a diagnosis.
Reference range
IgG: <1:64 (negative), 1:64-1:128 (equivocal), >=1:256 (positive); IgM: <1:64 (negative), >=1:64 (positive)N/A
No special preparation required. Patient may eat and drink normally before sample collection.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Colorado tick fever is a viral infection transmitted by the Rocky Mountain wood tick (Dermacentor andersoni). While often a self-limited illness lasting 1-2 weeks, it can occasionally cause more serious complications including meningitis, encephalitis, or hemorrhagic fever. The IgG/IgM panel helps confirm the diagnosis, which is important because symptoms can resemble other tick-borne diseases like Rocky Mountain spotted fever or tularemia. Early diagnosis allows for appropriate monitoring and supportive treatment. This test is particularly valuable in endemic areas where clinical diagnosis alone may be unreliable.
Frequently asked questions
How long does it take to get results?
Do I need to fast before this test?
Can this test tell me if I have been infected before?
Is Colorado tick fever serious?
How is Colorado tick fever treated?
Sources
- 1
- 2
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 10, 2026. · Read our editorial policy