Skip to content

Ctfviggigmserimp

Published: August 9, 2026Updated: August 14, 2026

This blood test detects IgG and IgM antibodies against Colorado tick fever virus to determine if you have been infected with this tick-borne illness.

Quick summary

{"Colorado tick fever is a viral infection spread by tick bites, primarily in the western United States","IgM antibodies indicate recent infection, while IgG antibodies suggest past exposure or immunity","Symptoms typically include fever, headache, muscle aches, and sometimes rash","Most cases resolve on their own within a week or two","Prevention focuses on avoiding tick bites when spending time in endemic areas"}

Medically reviewed by WellAlly Editorial TeamLast reviewed August 14, 2026Editorial policy

Key facts at a glance

LOINC
57773-4
Short code
CTFV IgG/IgM
Synonyms
CTFV IgG+IgM Ser-Imp
Category
cardiac
Sample
serum
Container
Serum separator tube (SST, gold top) or red top tube
Units
N/A
Ref low
64
Ref high
1
Fasting
false
Population
adult
Sex
all
Age range
0–120 years
Method
Enzyme Immunoassay (EIA) or Indirect Immunofluorescence Assay (IFA)
CPT
86635 (Colorado tick fever virus antibody)
SNOMED
4093005
Specimen volume
1.0 mL serum minimum, 2.0 mL preferred
Stability
Room temperature: 8 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C or below): 30 days. Avoid repeated freeze-thaw cycles.
Hemolysis max
50
Lipemia max
60
Icterus max
20
TAT
48–168 hours
Order
routine

What is this test?

The Colorado tick fever virus IgG and IgM test is a blood test that looks for antibodies your immune system produces in response to infection with the Colorado tick fever virus (CTFV). This virus is transmitted through the bite of infected Rocky Mountain wood ticks, primarily found in the western United States and southwestern Canada. The test specifically measures two types of antibodies: IgM, which appear early in infection and indicate recent exposure, and IgG, which develop later and can provide long-term immunity.

How is the test performed?

A healthcare professional will draw a small blood sample from a vein in your arm. This sample is then sent to a laboratory where technicians test it for the presence of IgG and IgM antibodies specific to the Colorado tick fever virus. The results are typically reported as either positive (antibodies detected) or negative (no antibodies detected), along with an interpretation of what these results mean for your health.

What do the results mean?

A positive IgM result with negative IgG suggests a recent or active infection, typically within the past few weeks. A positive IgG result with negative IgM indicates past exposure and possible immunity. If both IgG and IgM are positive, this suggests an ongoing or recent infection. Negative results for both antibodies mean no evidence of infection, though this could also occur if the test was done too early in the infection before antibodies have developed.

Reference range

IgG: Negative (< 1:64), Equivocal (1:64-1:128), Positive (>= 1:256); IgM: Negative (< 1:64), Equivocal (1:64-1:128), Positive (>= 1:256). Final interpretation: No evidence of infection, Past infection, Recent infection, or Acute infection based on IgG and IgM patterns.N/A

Specimen: serum

No special preparation required. Fasting is not necessary. Inform the laboratory of any recent tick exposure, travel to endemic areas, or symptoms consistent with Colorado tick fever.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Frequently asked questions

What are the symptoms of Colorado tick fever?
Symptoms typically appear 3-5 days after a tick bite and may include sudden onset of fever, severe headache, chills, muscle pain (myalgia), fatigue, and sometimes a rash. Some patients may also experience nausea, vomiting, or abdominal pain. The fever often comes in waves, and symptoms typically last about a week, though fatigue may persist for several weeks.
How is Colorado tick fever treated?
There is no specific antiviral treatment for Colorado tick fever. Management is supportive and includes rest, adequate hydration, and over-the-counter medications like acetaminophen or ibuprofen to reduce fever and relieve pain. Most healthy individuals recover fully without complications. In severe cases, hospitalization may be required for intravenous fluids and monitoring.
How can I prevent Colorado tick fever?
Prevention focuses on avoiding tick bites. When spending time in endemic areas (typically above 4,000 feet elevation in the western U.S.), wear long-sleeved shirts and long pants, use EPA-registered insect repellents containing DEET, perform thorough tick checks after outdoor activities, and promptly remove any attached ticks using fine-tipped tweezers. Checking pets for ticks and using tick prevention products is also recommended.
When should I see a doctor after a tick bite?
You should seek medical attention if you develop fever, headache, or other symptoms within 2-3 weeks after a tick bite. Also consult a doctor if you develop a rash (especially an expanding red rash that may indicate Lyme disease), if the tick was attached for more than 24 hours, or if you develop severe or worsening symptoms. Early evaluation is important for proper diagnosis and treatment.
  1. 1
    CDC - Colorado Tick FeverSource
  2. 2
    Mayo Clinic - Tick BitesSource

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.

Medical Disclaimer

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 14, 2026. · Read our editorial policy