Determining a cutoff for fetal lung maturity with lamellar body count testing

Lamellar body count: Marker for foetal lung maturation promoted by intra-amniotic infection and/or inflammation

OBJECTIVE

There is evidence indicating that the risk of respiratory distress syndrome is reduced in preterm neonates exposed to intra-amniotic infection and/or inflammation. We hypothesised that foetal lung maturation promoted by intra-amniotic infection and/or inflammation results in elevated lamellar body count (LBC) in amniotic fluid (AF). This study aimed to determine the relationship between LBC in AF and intra-amniotic infection and/or inflammation in patients with threatened preterm birth.

STUDY DESIGN

This was a retrospective cohort study of patients with threatened preterm birth. A total of 104 consecutive pregnant women underwent amniocentesis in the early preterm period [gestational age < 34 weeks] to evaluate intra-amniotic infection and/or inflammation and foetal lung maturity. Intra-amniotic infection was confirmed by positive AF culture results for aerobic/anaerobic bacteria, fungi, and genital mycoplasma. Intra-amniotic inflammation was defined as a positive AF matrix metalloproteinase-8 rapid test. Outcomes of the study population were compared according to LBC in AF using a cut-off of 15,000/mm³.

RESULTS

The rates of elevated LBC and intra-amniotic infection and/or inflammation were 23% (24/104) and 52% (54/104), respectively. The median LBC was significantly higher in patients with intra-amniotic infection and/or inflammation than in those without [median LBC, 9,000/mm³ (interquartile range, IQR: 3,000-39,000) vs. 3,000/mm³ (IQR: 2,750-5,000), p < 0.001]. Intra-amniotic infection and/or inflammation was observed in 96% (23/24) of patients with elevated LBC and 39% (31/80) of patients without elevated LBC (p < 0.001). On multivariable analysis, the presence of intra-amniotic infection and/or inflammation was significantly associated with elevated LBC with an odds ratio (OR) of 66.0 [95% confidence interval (CI) 6.6-664.4, p < 0.001], even after accounting for gestational age at amniocentesis being a significantly related factor for predicting elevated LBC with an OR of 1.5 (95% CI 1.1-2.0, p = 0.004).

CONCLUSION

LBC elevation was independently associated with the presence of intra-amniotic infection and/or inflammation in women with early threatened preterm birth (gestational age < 34 weeks). This finding may support the view that an intra-amniotic inflammatory response promotes foetal lung maturation that can be detected by elevated LBC in AF.

Diagnostic accuracy of lamellar body count as a predictor of fetal lung maturity: A systematic review and meta-analysis

Objective

This study aimed to synthesize evidence from published studies about the diagnostic accuracy of lamellar body count (LBC) as a predictor of fetal lung maturity.

Study design

We searched Medline (via PubMed), EBSCO, Web of Science, Scopus and the Cochrane Library for relevant published studies assessing the accuracy of LBC as a predictor of fetal lung maturity. Studies were classified according to the counting essays, centrifugation protocols, and the reported optimum cut off values. Data of the true positive, true negative, false positive, and false negative were extracted and analyzed to calculate the overall sensitivity and specificity of the LBC.

Results

Thirty-one studies were included in the final analysis. Fourteen studies reported data for centrifuged amniotic fluid (AF) samples, 13 studies reported data for uncentrifuged samples, and four studies did not have enough information about whether centrifugation was done. LBC showed an area under the curve >80% in diagnosing lung immaturity with variable cut off values. Pooled analysis showed that LBC a 100% specificity to exclude respiratory distress syndrome (RDS) at a cut off value of 15,000 and 100% sensitivity to diagnose RDS at a cut off value of 55,000.

Conclusion

Cases with LBC < 15,000 are considered to have lung immaturity while cases with LBC > 45,000 in centrifuged AF samples or >55,000 in uncentrifuged AF samples are likely to have mature lungs. Cases with LBC ranging between these maturity and immaturity limits should be considered for further evaluation by other lung maturity tests.

Predicting neonatal respiratory morbidity by lamellar body count and gestational age

AIMS

To develop a predictive model for assessing the risk of developing neonatal respiratory morbidity using lamellar body counts (LBCs) and gestational age (GA) to provide a more patient-specific assessment.

METHODS

Retrospective cohort study of patients' ≥32 weeks' gestation who received amniocentesis with LBC analysis over a 9-year period. Respiratory morbidity was defined as respiratory distress syndrome, transient tachypnea of the newborn or oxygen requirement for >24 h. Logistic regression analyses were used to predict the absolute risk and odds of respiratory morbidity as a function of GA and lamellar body count.

RESULTS

Two hundred and sixty-seven mother-infant pairs included in the analysis with 32 cases (12.0%) of respiratory morbidity. When compared to those without respiratory morbidity, neonates with respiratory morbidity had amniocentesis performed at an earlier median GA, had lower mean birthweight and had lower median LBC (P<0.01). The GA specific absolute risks and odds ratios for the presence of respiratory morbidity were calculated. The predicted absolute risks of neonatal respiratory morbidity ranged from 38% at 32 weeks to 6% at 40 weeks when LBC were 35,000/μL.

CONCLUSION

GA specific predicted risk of neonatal respiratory morbidity using LBC provides a statistical model, which can aid clinicians in individually counseling patients regarding the absolute risk of their neonate developing respiratory morbidity.

Amniotic fluid lamellar body count as a novel biochemical marker for timing elective caesarean delivery

The aim of this study is to evaluate the performance of amniotic fluid lamellar body count (LBC) on the timing of elective caesarean delivery (CS) at ≥ 39 weeks. After allocating the study group (group I, transient tachypnoea of newborn (TTN), n = 14), an age-matched control group (group II, no TTN, n = 79) was selected for amniotic fluid LBC analysis. The median amniotic fluid LBC levels in group I were significantly lower than in the control group. Furthermore, the median values of mean lamellar body volume, median lamellar body distribution width and lamellar bodycrit in group I were also significantly lower than in group II. The best amniotic fluid LBC value to predict TTN was 40.15 × 10(3)/μl, with 82.3% sensitivity and 64.3% specificity. The favourable sensitivity and specificity values to predict the TTN for amniotic fluid LBC may suggest using it as an elective caesarean delivery-time scheduling marker.

Increased neonatal morbidity despite pulmonary maturity for deliveries occurring before 39 weeks

OBJECTIVE

To compare neonatal outcomes following deliveries <39 weeks after confirmation of fetal lung maturity with scheduled deliveries ≥39 weeks.

METHODS

A retrospective cohort study examining neonatal outcomes of women who were delivered following documented fetal pulmonary maturity at 36, 37, and 38 weeks compared to women undergoing a scheduled delivery at 39, 40, and 41 weeks. The χ(2)-test and Student's t-test were used to compare categorical and continuous data, respectively.

RESULTS

Delivery prior to 39 weeks following fetal pulmonary maturity was associated with a 8.4% composite neonatal morbidity rate as compared to 3.3% for deliveries at 39 weeks or greater (relative risk [RR] 2.9; confidence interval [CI] 2.4-3.6). Neonatal respiratory morbidity was significantly higher (5.4%) for those delivering at less than 39 weeks with documented fetal pulmonary maturity as compared to 2.1% for those delivering at 39 weeks or greater (RR 3.0; CI 2.3-3.9). Increased neonatal morbidity persisted for those delivered prior to 39 weeks even after excluding all diabetics (p < 0.001). Significant increases in neonatal morbidity were noted for deliveries prior to 39 weeks regardless of the mode of delivery.

CONCLUSION

Despite fetal pulmonary maturity, delivery before 39 weeks is associated with significantly increased neonatal morbidity when compared to scheduled deliveries at 39 weeks or greater.

Amniotic lamellar body counts determined with the Sysmex XE-2100 analyzer to predict fetal lung maturity during diabetic and other complicated pregnancies

OBJECTIVE

The detection of amniotic lamellar bodies (LB) has been shown to be a rapid and simple way to assess fetal lung maturity (FLM). The maturity thresholds for LB vary due to different factors, one being the type of particle-count analyser used.

MATERIAL AND METHODS

The Sysmex XE-2100 hematological analyser was evaluated in determination of amniotic LB counts and compared with lecithin/sphingomyelin (L/S) and phosphatidylglycerol (PG) determination. We analysed 132 amniotic samples from a total of 109 mothers (71 diabetic) with 112 infants. Results. The correlation between the LB counts obtained with the Sysmex XE-2100 and our reference thin layer chromatography (TLC) phospholipid method was good. Samples with low L/S ratio (< or = 2.0) and no PG (i.e. premature fetal lung status), had low LB counts (n = 18, mean 8500/L, range 1000-26000), whereas 51 samples with mature fetal lung status had high LB counts (mean 63600/uL, range 20,000-139,000). In all our four cases of respiratory distress syndrome the LB counts were low (range 1000-28000/uL). The reference values for FLM determination were established: < or = 6000/microL for immature, values between 7000 and 35,000/uL for borderline results and >35,000/uL for mature. CONCLUSIONS. The amniotic LB count analysis with Sysmex XE-2100 has many advantages being a repeatable, inexpensive and quantitative method with a very short turn-around time. Consequently, our routine is to perform LB counts initially from all amniotic samples and only borderline LB results are analysed with TLC.