This minor constituent of pulmonary surfactant begins to increase appreciably in AF several weeks after the rise in lecithin.
Because PG enhances the spread of phospholipids on the alveoli, its presence indicates an advanced state of fetal lung development and function.
PG determination is not generally affected by blood, meconium, or other contaminants.
PG can be performed by TLC, so it can be determined alone or in conjunction with lecithin-to-sphingomyelin testing.
It may be reported qualitatively as positive or negative, where positive represents an exceedingly low risk of respiratory distress syndrome (RDS), or in a quantitative fashion, in which a value 0.3 is associated with a minimal rate of respiratory distress.
AmnioStat-FLM is an immunologic qualitative agglutination test for determining the presence of PG in AF. This test is specific, sensitive, and rapid. Results are not affected by moderate blood or meconium contamination. It requires <0.1 mL of specimen, which can be obtained by transabdominal amniocentesis or from a vaginal pool.
Normal range:
Mature fetal lung: positive and weak positive
Immature fetal lung: negative
Use
Assessing fetal lung maturity
Determining the ability of fetal lungs to produce sufficient quantities of pulmonary surfactant
Predicting the likelihood of the development of respiratory distress syndrome if the fetus were delivered
Interpretation
Increased in mature fetal lungs
Decreased in immature fetal lungs
Limitations
AmnioStat-FLM is not subject to artifacts associated with other lung surfactant tests.
TLC test can produce false-positive test results with meconium contamination and vaginal fluid contamination.
The absence of PG or low levels of PG cannot dependably predict the presence of RDS.
Diabetes, regardless of glucose control, delays PG production.