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Test Code LBC Lamellar Body Count, Amniotic Fluid

Important Note

This test is now run at RRMC, ordering name is LBC.

 

LBC test requires 2 ml of unspun amniotic fluid. Specimens collected 
from a vaginal pool are NOT acceptable. Specimens must be properly
labeled with patient's full name, date of birth, # weeks gestation
and date/time of collection.
 
Supplemantal testing by Lethicin-Sphingomyelin Ratio (LS Ratio) and
Phoshatidylglycerol (PG) may also be ordered by physician. These
tests will be sent to Peace Health Lab in Eugene.

Performing Laboratory

Mayo Medical Laboratories in Rochester

Reporting Name

Lamellar Body Count, AF

Specimen Type

Amniotic Fld


Specimen Required


Container/Tube: Amniotic fluid container or plastic vial

Specimen Volume: 2 mL

Collection Instructions:

1. Do not centrifuge

2. Amniotic specimens must be blood and meconium free.


Reject Due To

Hemolysis

Mild reject; Gross reject

Lipemia

NA

Icterus

NA

Other

Centrifuged specimen. Presence of blood or meconium

Specimen Stability Information

Specimen Type Temperature Time
Amniotic Fld Refrigerated (preferred) 28 days
  Ambient  7 days

Specimen Minimum Volume

0.75 mL

Day(s) and Time(s) Performed

Monday through Sunday; Continuously

Specimen Retention Time

2 weeks

Analytic Time

Same day/1 day

Reference Values

Immature: <15,000/mcL

Indeterminate: 15,000-50,000/mcL

Mature: >50,000/mcL

 

Cutoffs are based on consensus protocol (Neerhof M, Dohnal JC, Ashwood ER, et al: Lamellar body counts: a consensus on protocol. Obstet Gynecol 2001;97:318-320)

Useful For

Predicting fetal lung maturity and assessing the risk of developing neonatal respiratory distress syndrome, when performed during 32 to 39 weeks gestation

Method Name

Sysmex XN-9000, Platelet Count by Impedance Method

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

83664

LOINC Code Information

Test ID Test Order Name Order LOINC Value
LBC Lamellar Body Count, AF 19114-8

 

Result ID Test Result Name Result LOINC Value
LBCC Lamellar Body Count 19114-8
LBCI Interpretation In Process

Clinical Information

Fetal lung maturity testing is used to determine the risk for developing respiratory distress syndrome (RDS) in infants born prematurely (32-39 weeks). The risk for developing RDS is inversely related to gestational age and is the most common cause of respiratory failure in neonates. RDS is associated with preterm birth due to insufficient production of pulmonary surfactant. Pulmonary surfactant is synthesized by type II pneumocytes. Surfactant consists of 90% phospholipids (primarily phosphatidylcholine and phosphatidylglycerol) and 10% proteins (surfactant proteins [SP]-A, SP-B, SP-C). Surfactant is packaged into lamellar bodies and is excreted into the alveolar space where it unravels and forms a monolayer on alveolar surfaces. Lamellar bodies can also pass into the amniotic cavity and, hence, are found in amniotic fluid. The surfactant functions to reduce the surface tension in the alveoli, preventing atelectasis. When surfactant is deficient, the small alveoli collapse and the large alveoli become overinflated and stiff, which has been associated with increased risk of developing respiratory distress. The status of fetal lung maturity is reflected in the concentration of surfactant in the form of phospholipids and lamellar bodies present in amniotic fluid. Lamellar bodies are similar in size to platelets and can be quantified on a hematology analyzer utilizing the platelet channel and used to estimate fetal lung maturity.

Interpretation

Amniotic fluid lamellar body counts (LBC) above 50,000/mcL are predictive of fetal lung maturity.

 

Amniotic fluid LBC below 15,000/mcL are suggestive of fetal lung immaturity and increased risk of neonatal respiratory distress syndrome (RDS).

 

The main value of fetal lung maturity testing is predicting the absence of RDS. An immature test result for fetal lung maturity is less reliable in predicting the presence of RDS.(1)

Cautions

Surfactant secretion into the amniotic fluid is minimal prior to 32 weeks gestation.

 

Fetal lung maturity testing is not indicated beyond week 39.

 

Specimens must not be frozen or centrifuged. Freezing and centrifuging the amniotic fluid falsely decreases the lamellar body count.

Clinical Reference

1. Fetal Lung Maturity: ACOG Practice bulletin. Obstet Gynecol September 2008;112(3):717-726

2. Eby C, Lu J, Gronowski AM: Lamellar Body Counts Performed on Automated Hematology Analyzers to Assess Fetal Lung Maturity. Lab Med 2008;39(7):15

3. Haymond S, Luzzi V, Parvin C, Gronowski A: A Direct Comparison Between Lamellar Body Counts and Fluorescent Polarization Methods for Predicting Respiratory Distress Syndrome. Am J Clin Pathol 2006;126:894-899

4. Szallasi A, Gronowski A, Eby C: Lamellar Body Count in Amniotic Fluid: A Comparative Study of Four Different Hematology Analyzers. Clin Chem 2003;49(6):994-997

5. Grenache DG, Gronowski AM: Fetal lung maturity. Clin Biochem 2006;39:1-10

6. Neerhof M, Dohnal JC, Ashwood ER, et al: Lamellar body counts: a consensus on protocol. Obstet Gynecol 2001;97:318-320

Method Description

The Sysmex Automated Hematology Analyzer XN-9000 measures platelet count by the impedance method to quantify lamellar body counts.(Automated Hematology Analyzer/Transportation units XN series [XN-9000] Instructions for Use [North American Edition], Sysmex Corporation, Kobe, Japan. Feb 2014)