Lamellar Body Count and Stable Microbubble Test on Gastric Aspirates from Preterm Infants for the Diagnosis of Respiratory Distress Syndrome

Abstract

Background: Lamellar body count (LBC) in amniotic fluid is being used to identify infants at risk of respiratory distress syndrome (RDS) who would benefit from surfactant prophylaxis or very early therapy. The test in gastric aspirates of newborns has not been properly explored. Objective: The main objective of this research was to evaluate the performance of LBC alone or in combination with the stable microbubble test (SMT), done on gastric aspirates from preterm babies to predict RDS. Methods: A total of 34 preterm infants with RDS and 29 without RDS, with a gestational age between 24 and 34 weeks, were included in the study. Gastric fluid was collected in the delivery room. A diluent (dithiothreitol) allowed all samples to be processed, even the thickest and non-homogeneous ones, without centrifugation. The SMT was done for comparison. Results: The best cut-off value was <42,000 lamellar bodies/µl to predict RDS, with a sensitivity of 92% (95% CI 73–100%) and specificity of 86% (95% CI 77–95%). The area under the receiver-operating characteristic curve was 0.928 (95% CI 0.86–0.99). SMT showed similar results. LBC and SMT together in series (positive result if both tests were positive) showed a sensitivity of 100% and a specificity of 86%. Conclusion: LBC on gastric aspirates diluted in a solution of dithiothreitol can be rapidly and easily performed, and may be used alone or in combination with SMT as a predictor of RDS, allowing selective prophylaxis or very early treatment only in surfactant-deficient newborns.

Early Surfactant Guided by Lamellar Body Counts on Gastric Aspirate in Very Preterm Infants

“…Daniel et al [23] who also used LBC in GAS for diagnosing RDS found a cut-off value of 42,000/µl. Our lower cut-off value is partly due to centrifugation of the GAS, which can reduce LBC [15].…”

“…Our lower cut-off value is partly due to centrifugation of the GAS, which can reduce LBC [15]. Furthermore, we diagnose infants with moderate to severe RDS with need for surfactant supplementation, while Daniel et al [23] diagnosed all infants with RDS.…”

“…Dilution of GAS may be a problem in the LBC method and in other methods as the microbubble test [23], though polyhydramnios is seldom seen before week 30. Other problems related to these tests are related to their need of individual expertise.…”

The Stable Microbubble Test for Determining Continuous Positive Airway Pressure (CPAP) Success in Very Preterm Infants Receiving Nasal CPAP from Birth

“…More specific tests for surfactant deficiency such as measurement of surfactant proteins, lecithin/sphingomyelin ratios and phosphatidylcholine/sphingomyelin ratios require laboratories, are expensive and time-consuming and have not been applied to infants treated with CPAP. More recently, lamellar body count in gastric aspirate, a more objective test, has been found to be comparable to SMT in predicting RDS but requires a laboratory with a centrifuge and cell counter [16]. …”

Why Not Use a Surfactant Test for Respiratory Distress Syndrome?

“…In 2006, a small study showed the utility of the test to predict the need for surfactant in nonventilated preterm infants [4]. In a recent study, the test showed good sensitivity (94%) and specificity (86%) for the diagnosis of respiratory distress syndrome when performed in gastric fluid [5]. We have introduced the SMT as part of routine care of all very-low-birth-weight infants at our service, to assist in the decision to give early surfactant in symptomatic infants on CPAP.…”