Lamellar Body Count Reflex, Amniotic Fluid
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Predicting fetal lung maturity and assessing the risk of developing neonatal respiratory distress syndrome, when performed during 32 to 39 weeks gestation
Useful in cases in which lamellar body count results are indeterminate
Profile Information A profile is a group of laboratory tests that are ordered and performed together under a single Mayo Test ID. Profile information lists the test performed, inclusive of the test fee, when a profile is ordered and includes reporting names and individual availability.
|Test ID||Reporting Name||Available Separately||Always Performed|
|LBC||Lamellar Body Count, AF||Yes||Yes|
Reflex Tests Lists test(s) that may or may not be performed, at an additional charge, depending on the result and interpretation of the initial test(s)
|Test ID||Reporting Name||Available Separately||Always Performed|
|FLP||Fetal Lung Profile, AF||Yes||No|
Testing Algorithm Delineates situation(s) when tests are added to the initial order. This includes reflex and additional tests.
If lamellar body count is indeterminate (between 15,000-50,000/mcL), then FLP / Fetal Lung Profile, Amniotic Fluid (includes lecithin/sphingomyelin ratio and phosphatidylglycerol) is performed, at an additional charge, to aid in the risk assessment for respiratory distress syndrome.
LBC: Sysmex XE5000, Platelet Count by Impedance Method
FLP: Thin-Layer Chromatography (TLC) with Quantitation by Densitometry
Includes lecithin/sphingomyelin ratio (L/S) and phosphatidylglycerol (PG), semiquantitative on amniotic fluid.
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Lamellar Body Count Reflex, AF
Fetal Lung Maturity
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Collection Container/Tube: Amniotic fluid container
Submission Container/Tube: Plastic vial
Specimen Volume: 10 mL
Collection Instructions: Do not centrifuge.
Additional Information: Centrifuging the specimen may cause erroneous results.
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
10 mL; In the advent of indeterminate results this test will be forwarded for additional testing involving chromatographic determination of the L/S ratio. The 10 mL of specimen should be sent as an assurance this option can be exercised.
Visible hemolysis, reject
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
|Amniotic Fld||Refrigerated (preferred)||72 hours|
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
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 (see FLP / Fetal Lung Profile, Amniotic Fluid) 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.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
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)
Lamellar body count (LBC):
Amniotic fluid LBC >50,000/mcL is predictive of fetal lung maturity.
Amniotic fluid LBC <15,000/mcL is 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)
Fetal Lung Profile:
L/S ratio < 2.5 and PG absent: immature
L/S ratio > or = 2.5 and PG absent: indeterminate
LS ratio < 2.5 and PG trace: indeterminate
L/S ratio > or = 2.5 and PG trace: mature
PG present: mature
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Surfactant secretion into the amniotic fluid is minimal prior to 32-weeks gestation.
Fetal lung maturity testing is not indicated beyond week 39.
Specimens should not be frozen or centrifuged. Freezing and centrifuging the amniotic fluid falsely decreases the lamellar body count. Amniotic specimens should be blood and meconium free.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
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 Describes how the test is performed and provides a method-specific reference
The Sysmex Automated Hematology Analyzer XE-5000 measures platelet count by the impedance method to quantify lamellar body counts. (Automated Hematology Analyzer XE-5000 Instructions for Use [North American Edition], Code No. 461-2638-6, Date of Last Revision: December 2011)
One-dimensional thin-layer chromatography (TLC) technique is used for separating the phospholipids in amniotic fluid. The first step in the process involves extraction of the lipids present in the amniotic fluid using chloroform/methanol mixture. The extracted specimen is streaked onto a TLC plate and placed in tank 1 for prechromatography, a step that removes a component that otherwise comigrates with phosphatidylglycerol (PG). Lipids are then separated using tank 2. The separated lipids are made visible with dilute cupric acetate and charring. Lecithin to sphingomyelin (L to S) is determined using a scanning densitometer. The relative intensities of L and S are expressed as a ratio, and PG is reported from a visual observation of the plate and reported as present, absent, or trace. (Unpublished Mayo method)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
LBC: Monday through Sunday; Continuously
Monday through Friday; 2 p.m.
Saturday and Sunday; 11 a.m.
Weekdays: Sample delivery time is 7:00 a.m. to 4:30 p.m.
Set-up time up to 2:00 p.m.
Saturday: Sample delivery time is 7:00 a.m. to 3:00 p.m.
Set-up time is up to 11:00 a.m.
Sunday: Sample delivery time is 8:00 a.m.-1:00 p.m.
Set-up time is up to 11:00 a.m. (On call only)
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
LBC: 1 day/FLP reflex: 2 days
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
See Individual Unit Codes
Performing Laboratory Location The location of the laboratory that performs the test
Test Classification Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
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 Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
Lamellar Body Count, Amniotic Fluid
Fetal Lung Profile, Amniotic Fluid
83661-Fetal lung maturity assessment; L/S ratio (if appropriate)
84081-PG (if appropriate)
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
|Result ID||Reporting Name||LOINC Code|
|LBCC||Lamellar Body Count||In Process|