Lamellar Body Counts

Due to improvements in gestational age dating, maternal administration of corticosteroids that accelerate fetal lung maturity in at-risk pregnancies, and exogenous surfactant replacement therapies, the number of newborn deaths due to respiratory distress syndrome has declined considerably over the last 15 years.Most clinical laboratories in the United States have noted a steady decline in the number of fetal lung maturity tests that they perform each year.

Many obstetricians in the United States have indicated that laboratory tests for fetal lung maturity are no longer needed for patient care (Grenache DG et al. Clinica Chimica Acta 2010;411:1746-9).Furthermore, European physicians rarely, if ever, order these tests and yet the rates of infant death due to respiratory distress are no worse than they are in the US.

Currently, more than 80% of laboratories in the United States use the FLM II assay from Abbott Laboratories to assess fetal lung maturity. Unfortunately, Abbott recently announced that it will cease production of FLM II on Dec 31, 2011. In spite of decreasing clinical demand, many laboratories in the United States have validated Lamellar Body Counts (LBC) as a replacement for FLM II.

Type II pneumocytes package surfactant into intracellular storage granules called lamellar bodies, which are excreted into the alveolar space. Lamellar bodies appear in the amniotic fluid at 28 to 32 weeks and increase exponentially as gestation continues. Thus, LBC is a direct measurement of surfactant production. Due to the similar size of lamellar bodies and platelets, automated hematology analyzers can accurately count amniotic fluid lamellar bodies using the platelet channel.

Outcome-based studies have demonstrated that LBC performs at least as well as the TDx FLM II test (Ghidini A, et al. Arch Gynecol Obstet 2005;271:325-8, Haymond S et al. Am J Clin Path 2006;126:894-9 and Karcher R, et al. Am J Obstet Gynecol 2005; 193:1680). A meta-analysis calculated receiver-operating characteristic curves based upon data from six studies and showed the lamellar body count performed slightly better than the lecithin/sphingomyelin ratio in predicting respiratory distress (Wijnberger LD et al. BJOG 2001; 108:583).

A protocol and interpretive guideline have been published by a consensus panel (Neerhof, MG. Obstet Gynecol 2001;97:318-20).

LBC (counts/uL)


0 – 15,000


15,000 – 50, 000


>50, 000


These cutoff points appear to be applicable to lamellar body counts performed on either Sysmex or Beckman Coulter hematology analyzers using uncentrifuged specimens. However, each laboratory must validate their own reference ranges.

Amniotic fluid is a heterogeneous mixture of fluid, sloughed cells, hair and other fetal debris that can have varying effects on LBC measurement. Blood contamination can lead to false elevation of the lamellar body count because platelets are counted as lamellar bodies. Meconium has been shown to lower LBC. Mucus artificially increases LBC. Vaginal pool samples can be counted if they are free of mucus. Amniotic fluid specimens contaminated with meconium or mucus cannot be run through the hematology analyzer. If amniotic fluid appears bloody, a red cell count is performed. LBC can be reported if the RBC count is <30,000/uL. Specimens with higher RBC counts are rejected. Physicians can request that a fetal lung profile be sent to a reference laboratory if either LBC or FLM II is indeterminate or the specimen is unacceptable for testing.

Specimens should be delivered to the laboratory at ambient temperature. LBC are stable at room temperature for up to 10 days. Frozen samples are not acceptable because freezing decreases LBC.

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