Skip to content

Mycobacterium tuberculosis culture (preliminary growth screening)

Published: August 9, 2026Updated: August 16, 2026

This test helps detect the presence of *Mycobacterium tuberculosis*, the bacteria responsible for tuberculosis, by examining a sample for early signs of bacterial growth.

Quick summary

["A preliminary screening to check for possible tuberculosis infection through bacterial culture."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
90433-4
Short code
Mycobact prelim grow Spt Ql Cult
Synonyms
Mycobact prelim grow Spt Ql Cult
Category
chemistry
Sample
sputum
Container
Sterile sputum container
Units
N/A
Ref low
0.8
Ref high
1.2
Critical range
— – 5 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
organism-specific-culture
CPT
85610
SNOMED
396252006
Specimen volume
3-5 mL
Stability
Room temperature: 2h, Refrigerated: 24h
TAT
4–24 hours
Order
routine

Why This Test Matters

Tuberculosis (TB) is a serious lung infection caused by *Mycobacterium tuberculosis*. This preliminary culture screen is used to identify if your sample contains bacteria that may grow into TB over time. It’s not a definitive diagnosis but helps guide further testing if needed.

What to Expect Before the Test

You may be asked to provide a sample (often from sputum, a throat swab, or other bodily fluid) based on your symptoms or risk factors. The lab will examine the sample for early bacterial growth, which may take several days to weeks to confirm.

What Happens During the Test

The sample is placed in a special growth medium to detect if *Mycobacterium tuberculosis* is present. If bacteria grow, it may indicate an infection that requires further testing (like a confirmatory culture or PCR test).

What the Results Mean

A positive preliminary result suggests possible TB bacteria, but it’s not a final diagnosis. Follow-up tests (like a confirmatory culture or molecular test) will be needed to confirm or rule out TB infection.

Reference range

INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A

Specimen: sputum

Inform your healthcare provider if you are taking blood thinners. No special preparation required.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Mycobacterium Tuberculosis (MTB) Culture Screen

Frequently asked questions

What does a positive preliminary result mean?
A positive preliminary result means the lab detected potential *Mycobacterium tuberculosis* bacteria in your sample. This is an early step and may require additional testing to confirm if you have TB. Your healthcare provider will discuss next steps, such as further cultures or molecular tests, based on your symptoms and risk factors.
What if my preliminary result is negative?
A negative preliminary result means no detectable bacteria were found in this initial screening. However, TB can sometimes take time to grow in culture, so your provider may recommend repeat testing or other diagnostic methods if you have symptoms or risk factors for TB.
How long does it take to get results?
Results may take several days to weeks, depending on the lab’s processing time and whether the bacteria grow. Your healthcare provider will contact you once results are available. Follow-up testing may be needed for a definitive diagnosis.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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 16, 2026. · Read our editorial policy