Determination of fetal lung maturity by L/S ratio, “shake test” and phosphatidylglycerol in amniotic fluid.

Persistence Time of the Ring of Bubbles (PTRB): A method for the quantification of the Foam Test

“…Thus, by using the PTRB instead of the foam test in this population, the rate of false negatives was reduced by 17%. The rate of false negatives of the foam test in relation to the L/S ratio obtained in this study was higher than that shown in our previous work [3], This could be due to a larger proportion of samples obtained from type B and C diabetics in the present study.…”

“…None of the samples were visibly stained with blood or meconium. The foam test was performed not more than 30 minutes after the extraction of the samples, by the method described by CLEMENTS [6] and modified by the authors [3], äs follows: a) Two glass tubes, ISOinm length and 10mm diameter, numbered I and II, were used. b) The thermic environment was maintained at 25 °C.…”

“…Therefore PTRB was not measured after this time limit. The L/S ratio was performed by a different technician, äs first described by GLUCK [11] and standardized in our laboratory [3]. The diagnosis of RDS was done by a neonatologist who did not know about the results of this research.…”

Optical density at 650 nm in amniotic fluid, L/S ratio and foam test as indicators of fetal lung maturity

“…The samples were obtained from pregnancies with associated pathologies, mainly diabetes, sensitized Rh negative, etc. The L/S ratio was measured according to GLUCK'S technique, as previously reported [2], The foam test was done with a modification of the original technique described by CLEMENTS [4], also mentioned in our previous publication [2]. For the obtention of the OD at 650 nm, we proceeded first to separate the cells and debris from the rest of the amniotic fluid by centrifugation at 2230 g for 30 minutes in a conic tube; 3 ml were taken from the supernatant, and the optical density was determined in a Bausch & Lomb, Spectronic 20 spectrophotometer.…”

“…On the other hand, the foam test [4], which allows to obtain an immediate result and also does not require specially trained personnel, is a very good screening test although its value is limited due to the high percentage of false negatives reported [2,3,19]. Also, the presence of subjective factors that are responsible for a lack of reproductivity of the results has been reported [14], The measurement of the optical density (OD) at 650 nm of amniotic fluid, proposed by SBARRA et al [15,16,17] and later by COPELAND et al [5,6], was done in order to avoid the disadvantages of the L/S ratio, with a simple and sensitive method for estimating the FLM, which is readily available in many centers".…”