Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1050 page)

   
Normal range:
see Table 16.54.

TABLE 16–54. Values of L:S Ratio and Lung Maturity

   Use

   Traditional biochemical test to measure fetal lung maturity

   Interpretation

   Increased in mature fetal lungs (see Limitations and Table 16.54 for high ratios)

   Decreased in immature fetal lungs

   Limitations

   Labor-intensive test offered by few laboratories

   Offers no advantage over fluorescence polarization

   Sensitivity of >95%, specificity of 70%

   Blood and meconium contamination can affect result

   Definite exceptions to prediction of pulmonary maturity with L:S ratio >2.0

   Infant of a diabetic mother (L:S ratio >2.0 has been frequently seen in cases in which RDS developed)