Pilot Study-A Cost and Time Savings Comparison of Lamellar Body Count and FLM II

Rationale/Background: This pilot study is a prospective cohort analysis of two methods currently available at our institution for the determination of fetal lung maturity (FLM) using amniotic fluid. The investigators wish to explore a cost and time savings potential between these two available tests. The test most utilized for the determination of FLM is the evaluation of phospholipids from the amniotic fluid. In our particular institution, the relationship of surfactant to albumin (S/A ratio) is analyzed using a measured fluorescent polarization called the FLM II procedure performed on the TDx or TDxFLx chemical analyzer which is commercially available from Abbott Labs. This test is time-consuming and not available at all institutions.

Lamellar bodies are lamellated phospholipids that represent a storage form of surfactant (1). Because lamellar body diameter (range, 1-5 µm) is similar to that of small platelets, lamellar body counts (LBCs) can be obtained rapidly with use of the platelet channel of a hematology analyzer. The investigators wish to compare the difference in both cost and time to result for determining FLM for the LBC method and the FLM II. Our hypothesis is that the time to result will be significantly less using the LBC method, and the cost associated with this method over the traditional FLM II will be favorable.

Extensive research has shown the efficacy of analyzing fetal lung maturity using lamellar bodies (2-11). Since the efficacy of this method has been established, the adequacy of the lamellar body count in comparison to the FLM II is not in question in this study. While other studies have speculated that a cost and time savings would exist, no literature was found to answer this precise question. The authors feel this information could benefit the medical community from an economic standpoint.

Amniotic fluid collected at the time of amniotomy on term cesarean sections will be sent to OSUMC laboratory for FLM analysis using both a LBC and the FLM II. Our hypothesis is that both the time to result and cost using the LBC method will be substantially less.

Methodology Mechanism of Testing At present, FLM testing at Oklahoma State University Medical Center (OSUMC) is performed by TDx-FLM chemical analyzer manufactured by Abbott Labs. Most laboratories using the Abbott FLM-II assay for assessing fetal lung maturity follow the manufacturer's recommendations for interpreting the surfactant to albumin ratio. Thus, values greater than 55 mg/g are considered mature and values less than 40 mg/g immature. McElrath et al., reported a probability of respiratory distress syndrome (RDS) of 15% or less can be achieved with a S/A ratio cutoff of 60 mg or more at 28 weeks of gestation, 50 or more at 30 weeks, 40 or more at 33 weeks, 30 or more at 35 weeks, and 20 or more at 37 weeks (12).