Estado de revisión: Este documento fue publicado en su primera versión en Documentos de la revista Química Clínica 1996; 15(6): 445-449. La presente versión revisa dicha información, introduce aspectos nutricionales no tratados anteriormente e incorpora un análisis DAFO de la situación actual respecto a la evaluación del estatus de vitamina E.

In prevention of the respiratory distress syndrome (RDS), measurements of surface tension values (a biophysical property) of amniotic-fluid samples are correlated with their lecithin/sphingomyelin (L/S) ratios (a biochemical property). According to some authors, precipitation of phospholipid with cold acetone is essential for determining the L/S ratio, because it separates surfactant and nonsurfactant phospholipidic fractions. Here we report the first study of the ability of three amniotic-fluid components to decrease surface tension: The complete lipid extract (without precipitation), and the fractions precipitated and (or) remaining soluble after addition of cold acetone. Addition of increasing aliquots of lipid extracts to these three samples showed that: (a) measurement of surface tension rapidly and reliably indicates fetal lung maturity, and (b) both precipitated and soluble phospholipid fractions decrease surface tension similarly, making it unlikely that the precipitation step in fact separates surfactant and nonsurfactant material.

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