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Interpretive Handbook

Test 8929 :
Fetal Lung Profile, Amniotic Fluid

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Respiratory distress syndrome is a common complication of prematurity occurring in infants whose lungs lack the surfactant necessary for healthy lung inflation and air exchange. Surfactant is not produced in sufficient quantity until relatively late in gestation. It is primarily made up of phospholipids such as lecithin and phosphatidylglycerol, which can be detected in amniotic fluid and used as markers for fetal lung maturity. Both the lecithin/sphingomyelin (L/S) ratio and phosphatidylglycerol (PG) concentration increase with gestational age and correlate with lung maturity. Testing both the L/S ratio and the presence or absence of PG provides a better assessment of neonatal risk than the use of either test alone.

Useful For Suggests clinical disorders or settings where the test may be helpful

Determining the ability of fetal lungs to produce sufficient quantities of pulmonary surfactant


Assessing the risk of developing neonatal respiratory distress in fetuses delivered less than 39 weeks gestational age

Interpretation Provides information to assist in interpretation of the test results

L/S ratio <2.5 and PG absent: immature

L/S ratio > or =2.5 and PG absent: indeterminate

L/S ratio <2.5 and PG trace: indeterminate

L/S ratio > or =2.5 and PG trace: mature

PG present: mature

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

No significant cautionary statements

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.













> or =2.5






> or =2.5



Any ratio



All results will be called back.

Clinical References Provides recommendations for further in-depth reading of a clinical nature

1. Ashwood ER, Knight GJ: Clinical Chemistry of Pregnancy. In Tietz Textbook of Clinical Chemistry and Molecular Diagnosis, Fourth Edition, Edited by Carl A Burtis, Edward R Ashwood, and David E Bruns, St Louis, MO, Elsevier Saunders, 2006, pp 2188-2192

2. Kulovich MV, Hallman MB, Gluck L: The lung profile. I. Normal pregnancy. Am J Obstet Gynecol 1979;135:57-63

3. Hill LM, Ellefson R: Variable interference of meconium in the determination of phosphatidylglycerol. Am J Obstet Gynecol 1983;147:339-340

4. Ragozzino MW, Hill LM, Breckle R, et al: The relationship of placental grade by ultrasound to markers of fetal lung maturity. Radiology 1983;148:805-807

5. Ventolini G, Neiger R, Hood D, Belcastro C: Update on assessment of fetal lung maturity. J Obstet Gynaecol August 2005;25(6):535-538