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Fetal Lung Maturity - Lamellar Body Count

HOSPITAL LAB UPDATE

Clinical Significance

Respiratory distress syndrome (RDS) of the newborn is a common cause of newborn mortality in the United States. It is caused by a deficiency in the quantity and/or composition of pulmonary surfactant produced by the neonatal lung, which leads to alveolar collapse and neonatal hypoxia shortly after birth. Decisions regarding treatment and management rely partially on the results of fetal lung maturity (FLM) tests.
 

Detection

Laboratory assessment of fetal lung maturityassists obstetricians in estimating the risk of respiratory distress syndrome (RDS) when premature delivery of an infantis being considered. The status of fetal lung maturity is reflected in the concentrations of specific phospholipids and the number of surfactant‐containing particles, or lamellar bodies, in amniotic fluid. Since lamellar body volumes are similar to platelets, automated hematology analyzers can provide rapid and precise lamellar body counts (LBCs).
 

Recommended Use

When the Fetal Lung Maturity test (73514) is ordered, a Lamellar Body Count (LBC) is performed. If the LBC is in the Immature or Mature range, no further testing is performed. If however, the LBC is in the Borderline range an L/S ratio will be performed at an additional charge. We will also report the presence or absence of PG along with the L/S ratio.

The L/S ratio test (Lecithin/Sphingomyelin ratio) is a measure of two lung surfactants: lecithin and sphingomyelin. Lecithin is the most important lung surfactant and provides the greatest surface tension‐lowering properties of all surfactants.

Lecithin increases dramatically in the last few weeks of pregnancy. Sphingomyelin is a minor lung surfactant and that amount is consistent throughout pregnancy. It serves as a good baseline against which increasing amounts of lecithin can be compared.
 

Specimen Requirements:

10 mL amniotic fluid free from contamination and protected from light. Use amber vial. If specimen is not placed in amber vial, wrap with foil.
IMPORTANT: For reflex to L/S ratio, specimen must be at the lab before noon, otherwise the L/S ratio cannot be run until noon the following day.
TRANSPORT TEMPERATURE: Ice Slurry. Specimen stability is 1 day if sterile, refrigerated, and protected from light.
 

Reference Ranges:

Immature: <= 15,000 Borderline: 16,000 ‐49,000 Mature: >= 50,000
TESTING FREQUENCY:Monday ‐Friday
LAB TEST ORDER CODES
COMPUNET ORDER CODE 73514
PREMIER EPIC CODE LAB198
KETTERING EPIC CODE LAB732
 

For More Information Contact:

Paul Labbe, Vice‐President, Hospital Solutions: (937) 297‐8204, paul.r.labbe@questdiagnostics.com

  • Vicki Studebaker, Vice‐President, Testing Services: (937) 297‐8243, vicki.a.studebaker@questdiagnostics.com
  • Mark Shearer, Chemistry Director: (937) 297‐8236, mark.l.shearer@questdiagnostics.com