Understanding Your Laboratory Test: What It Is, Why It Matters, and What to Expect During the Procedure
This test detects whether bacteria can produce X and V factors, which are nutrients required for the growth of certain bacteria.
{"X factor (hemin) and V factor (NAD) are nutrients some bacteria need to grow","This test helps doctors identify the specific type of bacteria causing infection","The test is performed on bacteria isolated from a patient sample","Results help determine the most appropriate antibiotic treatment","It is commonly used to identify Haemophilus bacteria"}
Key facts at a glance
- LOINC
- 45046-0
- Short code
- XVFAC
- Synonyms
- Bacteria X & V Factors Islt Ql
- Category
- chemistry
- Sample
- serum
- Container
- Pure culture isolate on appropriate solid medium (e.g., chocolate agar, tryptic soy agar slant) submitted in a sterile container or transport system suitable for microbiology specimens
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- Culture isolation followed by satellite growth testing on X and V factor impregnated discs or strips; bacterial growth factor dependency assessed on culture medium (e.g., tryptic soy agar) with disks containing X factor (hemin), V factor (NAD), or both X+V factors
- CPT
- 87081
- SNOMED
- 404-3
- Specimen volume
- Not applicable; a viable pure culture isolate is required rather than a volumetric specimen. A single isolated colony is typically sufficient for factor testing.
- Stability
- Isolates should be tested as soon as possible after isolation; maintain viability by storing at 2-8°C (refrigerated) if testing is delayed; do not freeze. Most isolates remain viable for 24-48 hours under proper conditions.
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 24–72 hours
- Order
- routine
This laboratory test measures specific substances in a sample of your blood, urine, or other body fluid to help your doctor evaluate how well your body is functioning and to detect early signs of illness or infection.
The X and V factor test is a bacterial identification test that determines whether a bacterium can produce X factor (hemin) and V factor (NAD/nicotinamide adenine dinucleotide). These are essential nutrients that some bacteria cannot make on their own and must obtain from their environment. This test is performed on bacteria that have been isolated from a patient sample, such as blood, cerebrospinal fluid, or respiratory secretions.
Your doctor uses the results of this test to confirm or rule out a medical condition, monitor a health problem you already have, and guide decisions about the treatment plan and follow-up care that are right for you.
Different bacteria have different nutritional requirements. For example, Haemophilus influenzae (not the same as the flu virus) requires both X and V factors to grow. By testing for these factors, laboratories can help identify the specific bacteria causing an infection, which is crucial for selecting the right antibiotics and determining the appropriate treatment duration.
A trained healthcare professional will usually draw a small sample of blood from a vein in your arm or ask you to provide a urine sample at a clinic or laboratory. The collection takes only a few minutes, and the sample is then sent for analysis.
A pure culture of bacteria isolated from your sample is tested. The bacteria are grown on special media that lack X and V factors, and then small disks or strips containing these factors are placed on the culture. The laboratory observes whether the bacteria grow around the disks, indicating they can use the provided factors to multiply.
Reference range
Presence or absence reported qualitatively: Detected (Positive), Not Detected (Negative), or No growth. Identification of X and V factor dependent organisms (e.g., Haemophilus influenzae requires both X and V; Haemophilus parainfluenzae requires only V; Haemophilus ducreyi requires only X) is reported when applicable.N/A
No patient preparation required. Specimen is typically an isolate from a primary culture; no fasting or special patient conditions apply. Ensure proper aseptic technique during specimen collection.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
This test is primarily used to identify Haemophilus species, particularly Haemophilus influenzae, which can cause serious infections including meningitis, pneumonia, and ear infections. Knowing the exact type of bacteria helps doctors prescribe targeted antibiotics instead of broad-spectrum medications, which helps fight antibiotic resistance and ensures more effective treatment.
The test may also help differentiate other fastidious bacteria that have specific nutritional requirements. Accurate identification is essential for infection control measures and for determining if family members or close contacts need preventive treatment in certain cases.
Frequently asked questions
Do I need to prepare for this test?
Is the test painful?
How long does it take to get results?
What do the results mean?
Sources
- 1
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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