Skip to content

Ctfvigmseracnc

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

A blood test that detects IgM antibodies against Colorado tick fever virus to diagnose recent infection.

Quick summary

{"Detects early immune response to Colorado tick fever virus infection","IgM antibodies typically appear within 2 weeks of tick exposure","Results help confirm diagnosis along with symptoms and exposure history","The test uses a serum blood sample","Positive results indicate recent or active infection"}

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

Key facts at a glance

LOINC
13293-6
Short code
CTF IgM
Synonyms
CTFV IgM Ser-aCnc
Category
cardiac
Sample
serum
Container
Serum separator tube (SST/gold top) or plain red top tube
Units
N/A
Ref low
1.1
Ref high
1.4
Fasting
false
Population
adult
Sex
all
Age range
0–120 years
Method
Enzyme-linked immunosorbent assay (ELISA) or Immunofluorescence assay (IFA)
CPT
86635
SNOMED
371949004
Specimen volume
1.0 - 3.0 mL of serum
Stability
Room temperature: 24-48 hours; Refrigerated (2-8°C): 5-7 days; Frozen (-20°C or below): 2-4 weeks. Avoid repeated freeze-thaw cycles.
Hemolysis max
50
Lipemia max
300
Icterus max
20
TAT
24–168 hours
Order
routine

What is this test?

The Colorado tick fever virus IgM antibody test is a blood test that looks for IgM antibodies in your serum. IgM antibodies are the first type of antibodies your immune system produces when fighting a new infection. This test helps doctors determine if you have been recently infected with the Colorado tick fever virus, which is transmitted by the Rocky Mountain wood tick.

Why is this test performed?

Your doctor may order this test if you have symptoms of Colorado tick fever, especially if you live in or have recently visited areas where the disease is common (typically the western United States, particularly the Rocky Mountain region). Common symptoms include sudden high fever, severe headache, muscle pain, fatigue, and sometimes a rash. The test helps confirm whether your symptoms are caused by Colorado tick fever virus.

How is the test done?

A healthcare professional will draw a small blood sample from a vein in your arm. The blood is collected into a tube and sent to a laboratory for testing. The laboratory will analyze your serum to detect the presence of IgM antibodies specific to the Colorado tick fever virus.

What do the results mean?

A positive IgM result typically indicates a recent or current infection with Colorado tick fever virus, as IgM antibodies appear early in the infection and usually persist for a few weeks to months. A negative result could mean you do not have the infection, or the test was performed too early in the infection before detectable antibodies developed. Your doctor will interpret the results together with your symptoms, medical history, and potential tick exposure.

Reference range

Negative: < 1:16 titer or < 1.1 index; Equivocal: 1:16 to 1:32 titer or 1.1-1.4 index; Positive: >= 1:32 titer or >= 1.4 index. Refer to laboratory-specific reference ranges as methods may vary.N/A

Specimen: serum

No special preparation required. Fasting is not necessary. Inform the laboratory of recent travel history, tick exposure, or residence in endemic areas.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Frequently asked questions

How soon after tick bite do symptoms appear?
Symptoms of Colorado tick fever typically appear within 2 to 14 days after being bitten by an infected tick.
Do I need to fast before this test?
No, fasting is not required for this blood test. You can eat and drink normally before the test.
Is the test safe?
The test involves a routine blood draw, which is generally safe. You may experience minor bruising or soreness at the needle site.
Can the test give false results?
Like all tests, there is a small chance of false-positive or false-negative results. A false-negative may occur if the test is done too early before antibodies develop. False-positives are rare but can sometimes occur due to cross-reactivity with other similar viruses.
How is Colorado tick fever treated?
Treatment is primarily supportive and includes rest, fluids, and pain relievers for fever and aches. Most people recover within a few weeks. Severe cases may require hospitalization.
  1. 1
    CDC - Colorado Tick FeverSource
  2. 2
    Mayo Clinic - Colorado Tick FeverSource

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