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FLM Fluorescence Polarization Amniotic Fluid Test

Last updated May 26, 2019

Approved by: Krish Tangella MD, MBA, FCAP

The FLM Fluorescence Polarization Amniotic Fluid Test helps determine the level of pulmonary surfactant in the lungs of a developing fetus, by measuring its levels in the amniotic fluid.


What are other Names for this Test? (Equivalent Terms)

  • Fetal Lung Maturity Fluorescence Polarization Amniotic Fluid Test

What is FLM Fluorescence Polarization Amniotic Fluid Test? (Background Information)

  • Fetal lung maturity is the state of maximum development of the lungs of a fetus. Immature fetal lungs will be unable to function optimally by themselves, to provide oxygen and remove carbon dioxide, which places the newborn at risk for infant respiratory distress syndrome (IRDS)
  • Fetal lung maturity (or FLM) is determined by measuring the amount of a substance called pulmonary surfactant on the surface of the lungs. Pulmonary surfactant is produced by the cells of the small, pocket-like structures in lungs called alveoli
  • Pulmonary surfactant is a soapy substance that reduces surface tension between the alveoli and the surrounding fluid. Low surface tension is important for several reasons:
    • It maximizes compliance - the ability of the lungs to expand as they take in air and contract as they let it out
    • It prevents lung collapse at the end of contraction
    • It prevents fluid accumulation in the lungs
  • Pulmonary surfactant levels increase as the lungs of the fetus mature. By measuring its levels, the maturation status of the lungs may be estimated
  • The FLM Fluorescence Polarization Amniotic Fluid Test helps determine the level of pulmonary surfactant in the lungs of a developing fetus, by measuring its levels in the amniotic fluid. It is used to estimate the stage of development of the lungs in a fetus
  • The test makes use of probes that are equally able to bind to albumin, a protein in amniotic fluid, and pulmonary surfactant. The more pulmonary surfactant that is present, the more the probes will bind to it instead of albumin
  • The ratio of how much probe is bound to pulmonary surfactant relative to how much is bound to albumin indicates the level of pulmonary surfactant, and hence fetal lung maturity

What are the Clinical Indications for performing the FLM Fluorescence Polarization Amniotic Fluid Test?

Following are the clinical indications for performing the FLM Fluorescence Polarization Amniotic Fluid Test:

  • Fast breathing
  • Lapses in breathing
  • Low blood pressure
  • Fast heart rate
  • Discoloration

How is the Specimen Collected for FLM Fluorescence Polarization Amniotic Fluid Test?

Following is the specimen collection process for FLM Fluorescence Polarization Amniotic Fluid Test:

Sample required: Amniotic fluid 

Process of obtaining an amniotic fluid sample in adults (amniocentesis):

  • A local anesthetic is applied to the site of amniocentesis
  • A needle is inserted into the mother’s abdominal wall, through the uterus and into the amniotic sac
  • Ultrasound is used to guide the needle, as it punctures the sac away from where the baby is located
  • Approximately 20 ml of amniotic fluid is obtained, and the needle is withdrawn

Preparation required: No special preparation is needed prior to the test.

What is the Significance of the FLM Fluorescence Polarization Amniotic Fluid Test Result?

  • A low value (less than 35 mg pulmonary surfactant per g of albumin) may indicate infant respiratory distress syndrome

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

  • Certain factors, such as multiple births (e.g. twins, triplets, etc.), can interfere with the results of the FLM Fluorescence Polarization Amniotic Fluid Test

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider of the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

The following DoveMed website link is a useful resource for additional information:

https://www.dovemed.com/common-procedures/procedures-laboratory/amniotic-fluid-analysis/

Please visit our Laboratory Procedures Center for more physician-approved health information:

http://www.dovemed.com/common-procedures/procedures-laboratory/

References and Information Sources used for the Article:


Helpful Peer-Reviewed Medical Articles:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: March 30, 2016
Last updated: May 26, 2019