Strategic utilization of fetal lung maturity tests

Abstract

We have retrospectively investigated the diagnostic efficiency of the Abbott TDxFLM (fetal lung maturity) assay as compared to the lecithin/sphingomyelin ratio (LSR) and phosphatidylglycerol (PG) or PG/sphingomyelin (PG/S) ratio. Our results are consistent with other published studies. A review of the literature revealed that 1759 patients have been studied, and 213 neonates were found to have respiratory distress syndrome (RDS). This included samples from different sources and patients with various pathological conditions including diabetes. The TDxFLM assay has the highest sensitivity, followed by PG and LSR. The specificity of LSR is only slightly better than TDxFLM, whereas PG is the least specific. While the LSR assay y thin layer chromatography is affected by blood and meconium, the PG test by AmnioStat-FLM is not. A study on the effect of serum, whole blood and meconium on the TDxFLM assay revealed that blood elevated its value, but serum and meconium depressed the result. A sample contaminated with meconium may be tested and the result interpreted with the same degree of confidence if maturity is indicated. However, bloody specimens require a confirmatory test, such as PG measurement with the AmnioStat-FLM assay. On consideration of the diagnostic efficiency of the FLM tests, we propose a sequential testing strategy to optimize the use of the laboratory and clinical care. The use of the TDxFLM assay is suggested as the initial test. If the sample is contaminated with blood, or when the result falls within the indeterminate region, the AmnioStat-FLM will be used as a second test. This strategic utilization of FLM tests will provide cost effective high quality patient care.