L/S ratio <2.0 indicates an increased risk of respiratory distress syndrome (RDS) at delivery. L/S ratio <1.5 indicates a very high risk of developing RDS.

Which of the following statements regarding the L/S ratio is TRUE?

The correct answer is highlighted below

A ratio of 2:1 or greater usually indicates adequate pulmonary surfactant to prevent respiratory distress syndrome (RDS)

A ratio of 1.5:1 indicates fetal lung maturity in pregnancies associated with diabetes mellitus.

Sphingomyelin levels increase during the 3rd trimester causing the L/S ratio to fall slightly during the last two weeks of gestation.

A phosphatidylglycerol (PG) spot indicates the presence of meconium in the amniotic fluid

Lecithin is in direct ratio with sphingomyelin

Heparin contamination is characterized by an elevation in the aPTT test and can also cause an increased PT test as well. Reptilase time tests are used to elimate the effects of heparin contamination as the reagents and method are resistant to the effects of antithrombin III, unlike the PT and aPTT tests. Therefore, it would be expected that a patient sample containing pre-analytical heparin contamination will show an increased aPTT (and sometimes PT as well) while showing a normal reptilase time.

A specimen drawn from an indwelling catheter that was contaminated by heparin would be indicated by: