Prediction of RDS from amniotic fluid analysis : a comparison of the prognostic value of TLC and infra-red spectroscopy

nfra-red (IR) spectroscopy was recently shown to be a sensitive method for the determination of fetal lung maturity (Liu et al., 1998). The present study was undertaken to validate the newly developed method for prediction of RDS (Respiratory Distress Syndrome). Samples of amniotic fluid were obtained by amniocentesis from 86 patients between the 28th and 41st week of pregnancy. A small volume, 35μl, of amniotic fluid was used to acquire infra-red spectra with a commercial spectrometer. The lecithin/sphingomyelin (L/S) ratio was determined separately by TLC (thin layer chromatography). A calibration model was established using a partial least squares regression analysis which quantitatively correlated 145 IR spectra with the TLC-based L/S ratios; the correlation coefficient was 0·95. The model was then validated using a total of 111 spectra which also showed a high correlation coefficient (r=0·91). Based upon the clinical data associated with these samples, the prediction accuracy for the presence of RDS was 67 per cent for TLC and 83·3 per cent for IR. The accuracy for predicting the absence of RDS was 93·4 per cent for TLC and 96·8 per cent for IR. We conclude that IR spectroscopy has the potential to become the clinical method of choice for predicting RDS from amniotic fluid analysis.