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THE RELATION OF FLUORESCENCE POLARIZATION VALUES TO LECITHIN SPHINGOMYELIN RATIOS (L/S) IN AMNIOTIC FLUID (AF)

Fluorescence polarization (FP) measures the microviscosity of phospholipid micelles. The technique has been evaluated in both artificial solutions and in AF and its usefulness in determining gestational age and lung maturity examined.We have shown that in lipid dispersions of known composition and in amniotic fluid the FP value correlates directly with the L/S ratio. Gestational age was studied in 97 serial samples from 19 isoimmunized pregnancies. There was a significant change in slope of FP values vs. gestational age occurring between 29 to 35 weeks (mean = 31.5 wks). In single samples from 120 pregnancies a significant correlation was also found between FP and L/SThus FP values correlate well with both gestational age and lung maturity.The determination of fluorescent polarization is precise with a coefficient variation of 0.48%. It can be performed rapidly (45 min)and is technically easy. This physical method therefore offers a great advantage over the currently available chemical methods. (Supported by NHLI HL-14218)