Understanding This Medical Test: What It Measures, Why It Is Ordered, and What Your Results Mean for Your Health
This laboratory test uses a special staining technique to detect acid-fast bacteria, such as tuberculosis, in the amniotic fluid collected during pregnancy.
{"A specialized microscopy test performed on amniotic fluid sample","Uses acid-fast stain to identify tuberculosis and related bacteria","Helps diagnose bacterial infections that may affect pregnancy and fetal health","Results guide treatment decisions if infection is detected","Sample is collected through amniocentesis procedure"}
Key facts at a glance
- LOINC
- 88156-5
- Short code
- Acid fast Stn Amn
- Synonyms
- Acid fast Stn Amn
- Category
- chemistry
- Sample
- fluid
- Container
- Sterile tube
- Units
- N/A
- Ref low
- 10
- Ref high
- 40
- Critical range
- — – 500 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- acid-fast-stain
- CPT
- 84484
- SNOMED
- 302774002
- Specimen volume
- 2-5 mL
- Stability
- Room temperature: 2h, Refrigerated: 24h
- Hemolysis max
- 300
- TAT
- 4–24 hours
- Order
- routine
What is this test and what can it tell your healthcare provider about your health and how your body is working?
The acid-fast stain test is a laboratory examination of amniotic fluid that uses a special dye (acid-fast stain) to detect certain bacteria, primarily those belonging to the Mycobacterium genus, which includes the bacteria that cause tuberculosis (TB). This test is performed under a microscope to identify the characteristic appearance of acid-fast bacteria, which retain the red dye even when washed with acid-alcohol.
Why is this test performed, and in what situations does your healthcare provider typically order it for you?
This test is typically ordered when a pregnant woman shows signs of a possible mycobacterial infection, or when there is concern about tuberculosis exposure. It helps healthcare providers determine if a bacterial infection is present in the amniotic fluid, which could potentially affect the developing baby. Early detection of such infections is crucial for timely treatment and to prevent complications during pregnancy.
How is the sample for this test collected, and what should you expect when the specimen is taken from you?
The amniotic fluid sample is collected through a procedure called amniocentesis. During this procedure, a thin needle is inserted through the abdomen into the uterus to withdraw a small amount of amniotic fluid. The procedure is performed under ultrasound guidance to ensure safety. While amniocentesis carries a small risk of miscarriage, it is considered safe when performed by experienced healthcare providers.
What do the results of this test mean, and how do healthcare providers interpret normal and abnormal values?
A negative result means no acid-fast bacteria were detected in the amniotic fluid sample. A positive result indicates that acid-fast bacteria were found, which may suggest an infection such as tuberculosis. However, further testing (such as culture) is often needed to confirm the specific type of bacteria and determine the most appropriate treatment. Your healthcare provider will discuss your results with you and recommend next steps if needed.
Reference range
Adult: 10-40 U/LN/A
No special preparation required. Avoid fatty meals before the test if possible.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
This test is clinically significant for detecting mycobacterial infections in pregnant women, particularly tuberculosis, which can have serious implications for both maternal and fetal health. Tuberculosis during pregnancy can lead to low birth weight, premature birth, or even fetal death if left untreated. Early detection through acid-fast staining allows for prompt antibiotic treatment, reducing the risk of complications. The test is especially important for women at high risk of TB, including those with HIV, those from regions with high TB prevalence, or those who have been in contact with TB patients.
Frequently asked questions
Is the amniocentesis procedure painful?
How long does it take to get results?
Does a positive result mean my baby has TB?
Is this test safe during pregnancy?
What happens if the test is positive?
Sources
- 1
- 2
- 3
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 17, 2026. · Read our editorial policy