Complete Blood Count (CBC) Test: What It Is and Why It Matters
This blood test analyzes gene expression patterns to determine the likelihood of a bacterial infection.
{"Measures mRNA expression to detect bacterial infection","Requires a small whole blood sample","Helps distinguish bacterial from viral infections","Results show a score indicating infection probability","Guides appropriate antibiotic treatment decisions"}
Key facts at a glance
- LOINC
- 112324-9
- Short code
- BACTLIK
- Synonyms
- Bact infn lhd Bld Clc.mRNA exprs-Scre
- Category
- chemistry
- Sample
- whole-blood
- Container
- PAXgene Blood RNA tube (BD Vacutainer with RNA stabilization reagent)
- Units
- N/A
- Ref low
- 1.5
- Ref high
- 9
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–99 years
- Method
- calculated-mrna-expression
- CPT
- 81513
- Specimen volume
- 2.5 mL whole blood
- Stability
- Ambient: up to 72 hours in PAXgene tube; Refrigerated (2-8°C): up to 5 days; Frozen (-20°C or below): up to 8 weeks. RNA isolated from sample should be stored at -80°C for long-term stability.
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 8–24 hours
- Order
- routine
What is a complete blood count (CBC), and what does it measure in your blood?
The Bacterial Infection Likelihood test is a molecular diagnostic tool that examines specific genes in your blood to estimate the probability of a bacterial infection. By analyzing mRNA expression patterns—changes in gene activity that occur in response to infections—this test can help determine whether your infection is more likely caused by bacteria rather than viruses or other causes.
How is a complete blood count (CBC) performed, and what can you expect during the blood draw?
A healthcare professional will draw a small blood sample from a vein in your arm. This sample is then sent to a laboratory where scientists measure the expression levels of specific genes associated with the immune response to bacterial infections. Using mathematical calculations, the lab produces a score that indicates how likely it is that you have a bacterial infection.
Why might your doctor order a complete blood count (CBC) as part of your routine care or to check a symptom?
Your doctor may order this test if you have symptoms of an infection (such as fever, fatigue, or body aches) and needs to determine whether it is bacterial or viral. This distinction is important because bacterial infections require antibiotics, while viral infections do not. Knowing the type of infection helps your doctor prescribe the right treatment and avoid unnecessary antibiotic use.
What do your complete blood count (CBC) results mean, and what should you discuss with your doctor?
Results are reported as a score indicating the likelihood of bacterial infection. A higher score suggests a greater probability of bacterial infection, while a lower score suggests the infection is unlikely to be bacterial or may be viral. Your doctor will interpret these results along with your symptoms, physical exam, and other test results to decide on the best treatment plan for you.
Reference range
Follicular: 1.5-9.0 mIU/mLN/A
No special patient preparation required. Specimen should be collected prior to initiation of antimicrobial therapy when possible to avoid false-negative results.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
This test plays a crucial role in guiding appropriate antibiotic therapy. By helping distinguish bacterial from viral infections, it supports better clinical decision-making and helps reduce unnecessary antibiotic prescriptions. This is important because overuse of antibiotics contributes to antibiotic resistance, a growing global health concern. The test provides objective, science-based information that can improve patient outcomes and ensure more precise treatment.
Frequently asked questions
Do I need to fast before this test?
How long does it take to get results?
Does the test hurt?
Can this test identify the specific type of bacteria?
Is this test accurate?
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 16, 2026. · Read our editorial policy