Obstetrics & Gynecology Track the topics, authors and articles important to you
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Obstetrics & Gynecology 1999;93:387-391
© 1999 by The American College of Obstetricians and Gynecologists
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by LEWIS, P. S.
Right arrow Articles by DOMBROWSKI, M. P.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by LEWIS, P. S.
Right arrow Articles by DOMBROWSKI, M. P.

ORIGINAL RESEARCH

Amniotic Fluid Lamellar Body Count: Cost-effective Screening for Fetal Lung Maturity

PAMELA S. LEWIS, MD, MICHELE R. LAURIA, MD, JEFFERY DZIECZKOWSKI, MD, GREGORY O. UTTER, MD and MITCHELL P. DOMBROWSKI, MD

From the Departments of Obstetrics and Gynecology, Pathology, and Internal Medicine, Wayne State University, Hutzel Hospital, and the Department of Obstetrics and Gynecology, Grace Hospital, and St. John Hospital and Medical Center, Detroit, Michigan.

Address reprint requests to: Pamela S. Lewis, MD, Hutzel Hospital, Department of Maternal Fetal Medicine, 4707 St. Antoine Boulevard, Detroit, MI 48201, E-mail: plewis{at}med.wayne.edu


   Abstract
Top
Abstract
Materials and Methods
 Results
 Discussion
 References
 
Objective: To create a highly specific cascade testing scheme for fetal lung maturity using the lamellar body count, lecithin/sphingomyelin ratio (L/S), and phosphatidylglycerol.

Methods: A nondedicated hematology analyzer (Sysmex NE 1500, Toa Medical Electronics, Los Angeles, CA) was used to determine the lamellar body counts of 209 unspun amniotic fluid specimens. Maximally specific lamellar body count cutoffs for biochemical maturity and immaturity were determined using receiver operating characteristic curves. Biochemical lung maturity was defined as either a mature L/S ratio or phosphatidylglycerol. Biochemical lung immaturity was defined as both an immature L/S ratio and an immature phosphatidylglycerol.

Results: A lamellar body count of less than 8000 (n = 17) was 100% specific for biochemical lung immaturity (positive predictive value = 100%, negative predictive value = 86%). A lamellar body count of greater than 32,000 was 98% specific for biochemical lung maturity (positive predictive value = 99%, negative predictive value = 63%).

Conclusion: Testing only specimens where the lamellar body count was greater than 8000 and less than or equal to 32,000 for the L/S ratio and phosphatidylglycerol would preclude the need for 76% of all L/S and phosphatidylglycerol assays. Because the lamellar body count is quick, simple, and universally available, it could serve as an extremely cost-effective screening test for fetal lung maturity.

The lecithin/sphingomyelin ratio (L/S) as developed by Gluck et al is one of the most widely used assays for the assessment of fetal lung maturity.1 While it is a reliable test, it is expensive, time-consuming, and not universally available. Many institutions also incorporate a phosphatidylglycerol assay to complete the fetal lung maturity profile. This test is also expensive, requiring time and trained laboratory personnel.

The lamellar body count, also known as the lamellar body number density, was first described by Dubin in 1989.2 The lamellar body is a surfactant-containing lamellated structure that is secreted by the type II pneumocyte (Figure 1Go).3 Because lamellar body diameter is between 1–5 µm, lamellar body counts can be determined using the platelet channel of a commercial cell counter. Therefore, it is a very quick, simple, and inexpensive test. The unit of measurement is number of lamellar bodies counted per microliter of amniotic fluid. As with platelets, it is reported as a value in the thousands. Several studies have shown lamellar body counts to be accurate predictors of fetal lung maturity.2,4–11 Most of these studies have used spun fluid measured on an automated hematology analyzer and report a variety of values as indicative of maturity.



View larger version (148K):
[in this window]
[in a new window]
  		Figure 1. Electron micrograph of a ductal epithelial cell of human fetal lung showing lamellar bodies (original magnification x 17,500).

 
Performing easy and inexpensive tests for lung maturity first, and more expensive tests only if initial tests are indeterminant has been advocated as a cost-effective method of screening for fetal lung maturity.3,12,13 Our purpose was to determine if the lamellar body count is a reliable predictor of biochemical lung maturity. In addition, the utility of a cascade testing regime using lamellar body count as an initial step is examined.


   Materials and Methods
Top
Abstract
 Materials and Methods
Results
 Discussion
 References
 
Amniotic fluid specimens were obtained between January and November 1996 by transabdominal amniocentesis on patients undergoing fetal lung maturity evaluation. All specimens received having more fluid than for our standard analysis were included. Only one specimen per subject was included. Lecithin/sphingomyelin ratios and phosphatidylglycerol concentrations were determined using a modification of Gluck’s technique that eliminates the steps of routine centrifugation, filtration, and acetone precipitation.14 Studies done at our institution and other institutions using this technique show an L/S ratio of 3.5:1 or a phosphatidylglycerol concentration of greater than 1.0% indicate lung maturity.14–16

Lamellar body count was quantified using the platelet channel of a nondedicated automated hematology analyzer, Sysmex NE 1500 (Toa Medical Electronics, Los Lamitos, CA). The instrument was calibrated every 8 hours according to manufacturer guidelines. All clear specimens were unspun. Those containing blood or meconium were centrifuged at 500g x 3 minutes. The instrument was primed once, then each sample was assayed in duplicate and the average calculated.

A sample was considered mature if either the L/S ratio or phosphatidylglycerol was mature. The ability of the lamellar body count to predict fetal lung immaturity and maturity was evaluated by calculating the sensitivity and specificity of each lamellar body count value from 0–268,000. Lamellar body counts from clear unspun specimens were analyzed separately from those that were centrifuged to avoid contamination. Receiver operating characteristic curves were then constructed to determine the lamellar body count that would optimize the test’s ability to assess biochemical lung maturity and immaturity.


   Results
Top
Abstract
 Materials and Methods
 Results
Discussion
 References
 
A total of 209 clear samples were evaluated. The lamellar body count values ranged from 1000 to 268,000. The intra-assay variability was 1.3%. A lamellar body count less than or equal to 8000 was 100% specific for biochemical lung immaturity based on both an immature L/S ratio and phosphatidylglycerol value (Table 1Go). A lamellar body count greater than 32,000 was 98% specific for biochemical lung maturity based on either the L/S ratio or phosphatidylglycerol values being positive (Table 1Go). Using lamellar body count cutoffs of less than or equal to 8000 and greater than 32,000 maximizes the sensitivity and specificity of the test to predict biochemical fetal lung immaturity and maturity, respectively (Figures 2Go and 3Go). Using these cutoffs, 76% of all phosphatidylglycerol and L/S assays could have been eliminated.


View this table:
[in this window]
[in a new window]
  		Table 1. Performance of Lamellar Body Count to Predict Biochemical Lung Maturity and Immaturity
 


View larger version (12K):
[in this window]
[in a new window]
  		Figure 2. Receiver operating characteristic curve using lamellar body counts to predict biochemical fetal lung immaturity.

 


View larger version (11K):
[in this window]
[in a new window]
  		Figure 3. Receiver operating characteristic curve using lamellar body counts to predict biochemical fetal lung maturity.

 
Thirty-five specimens were contaminated with blood or meconium. Their lamellar body count ranged from 5000 to 255,000. These specimens were gently centrifuged. The receiver operator characteristic curves did not change when these specimens were added to the clear unspun samples.


   Discussion
Top
Abstract
 Materials and Methods
 Results
 Discussion
References
 
This is a unique investigation because we evaluated lamellar body count performance as part of a panel of tests for fetal lung maturity and used biochemical maturity, not respiratory distress syndrome (RDS) as the outcome. Our definition of biochemical maturity (mature L/S ratio or phosphatidylglycerol) is based on previous studies at our institution of respiratory outcome of 900 newborns delivered within 3 days of amniotic fluid collection.16 In addition, we studied unspun amniotic fluid and used a nondedicated Sysmex analyzer rather than a Coulter analyzer. Our number of 209 specimens exceeds that of the two previous studies using unspun fluid.2,4

Table 2Go lists previously published clinical trials addressing the ability of the lamellar body count to predict fetal lung maturity. The outcome variable in all of these studies was neonatal RDS. Our study, which used biochemical maturity as the end point, found the value of 32,000 to be maximally predictive of maturity. This is a value somewhat lower than previously published for unspun specimens. A possible explanation for our lower value could be our exclusive use of a Sysmex counter. The Coulter instruments used in prior investigations have 50 µm apertures whereas Sysmex has an 80 µm aperture. We postulate that the larger aperture may allow multiple lamellar bodies to pass through the channel simultaneously but only be counted as one lamellar body, leading to lower counts.


View this table:
[in this window]
[in a new window]
  		Table 2. Comparison of Studies of Lamellar Body Count Indicating Fetal Lung Maturity
 
There are now several accepted tests to assess fetal lung maturity. The most common of these are the lecithin/sphingomyelin ratio, phosphatidylglycerol, foam stability index ("shake test"), fluorescence polarization, and optical density at 650 nm.17 With this large armamentarium of tests, several authors have proposed pathways to maximize specificity while reducing cost and time. Two authors recommend using variations of the foam stability index as a first line test, reserving more expensive tests for negative or equivocal values.12,13 More recently Greenspoon et al4 proposed using the lamellar body count as the initial test with no further testing for values over or equal to 46,000. They did not assess the lamellar body count value below which the risk of immaturity is so high as to preclude further testing. Only one author has specifically reported a lamellar body count value below which the risk of immaturity is exceedingly high.6 However, no one has made recommendations for cutoff below which further testing would be unnecessary. Extrapolating from published data10,11 a lamellar body count of less than 10,000 is rarely associated with biochemical maturity. This value correlates well with our number of 8000.

Based on our findings we propose a new, three-armed testing scheme (Figure 4Go), that includes no further testing for a lamellar body count less than or equal to 8000. This third arm would eliminate an additional 8% (17 of 209) of L/S ratio and phosphatidylglycerol assays at our institution without impairing test performance. Using this proposed testing cascade at our institution would result in expensive L/S and phosphatidylglycerol assays being performed on only 24% of specimens.



View larger version (20K):
[in this window]
[in a new window]
  		Figure 4. Schematic representation of the fetal lung maturity cascade. LBC = lamellar body count; L/S = lecithin sphingomyelin ratio; PG = phosphatidylglycerol.

 
To further simplify testing we used unspun samples. In so doing, we eliminated a step prone to variation. It has been shown that centrifugation at 500g for 5 minutes can decrease the lamellar body count by 10% to 40%.2 Of interest, we had 35 specimens which contained particulate meconium or were grossly bloody. These were not included in the data presented in the results. Centrifugation was performed on these samples per our laboratory protocol prior to L/S ratio and/or phosphatidylglycerol determination. When we measured their lamellar body count and added these 35 samples to our data pool, our results did not change.

The lamellar body count used in a cascade testing scheme could eliminate the need for 76% of phosphatidylglycerol and L/S ratio assays. As the cost of the lamellar body count is similar to that of a complete blood count, performing phosphatidylglycerol and L/S ratio only on transitional specimens (those with lamellar body count between 9000 and 32,000) is a very cost-effective alternative to our current method. Based on pricing from a leading national reference laboratory, our cascade testing scheme would result in a total institutional savings of $57.00 per patient when compared with running L/S ratio and phosphatidylglycerols. The savings to the patient or insurance carrier would be about $85.00 per patient. The lamellar body count is an encouraging new test for lung maturity.


   Footnotes
 
PII S0029-7844(98)00416-5

Received May 4, 1998. Received in revised form August 20, 1998. Accepted August 27, 1998.


   References
Top
Abstract
 Materials and Methods
 Results
 Discussion
 References
 
1. Gluck L, Kulovich MV, Borer RC, Brenner PH, Anderson GG, Spellacy WN. Diagnosis of the respiratory distress syndrome by amniocentesis. Am J Obstet Gynecol 1971;109:440–5.[Medline]

2. Dubin SB. Characterization of amniotic fluid lamellar bodies by resistive-pulse counting: relationship to measures of fetal lung maturity. Clin Chem 1989;35:612–6.[Abstract/Free Full Text]

3. Snyder JM, Johnston JM, Mendelson CR. Differentiation of type II cells of human fetal lung in vitro. Cell Tissue Res 1981;220:17–25.[Medline]

4. Greenspoon JS, Rosen DJD, Roll K, Dubin SB. Evaluation of lamellar body number density as the initial assessment in a fetal lung maturity test cascade. J Reprod Med 1995;40:260–6.[Medline]

5. Pearlman ES, Baiocchi JM, Lease JA, Gilbert J, Cooper JH. Utility of a rapid lamellar body count in the assessment of fetal maturity. Clin Chem 1991;95:778–80.

6. Bowie LJ, Shammo J, Dohnal JC, Farrell E, Vye MV. Lamellar body number density and the prediction of respiratory distress. Clin Chem 1991;95:781–6.

7. Dalence CR, Bowie LJ, Dohnal JC, Farrell EE, Neerhof MG. Amniotic fluid lamellar body count: a rapid and reliable fetal maturity test. Obstet Gynecol 1995;86:235–9.[Abstract]

8. Ashwood ER, Palmer SE, Taylor JS, Pingree SS. Lamellar body counts for rapid fetal lung maturity testing. Obstet Gynecol 1993;81:619–24.[Abstract/Free Full Text]

9. Fakhoury G, Daikoku NH, Benser J, Dubin NH. Lamellar body concentrations and the prediction of fetal pulmonary maturity. Am J Obstet Gynecol 1994;170:72–6.[Medline]

10. Lee IS, Cho YK, Kim A, Min WK, Kim KS, Mok JE. Lamellar body count in amniotic fluid as a rapid screening test for fetal lung maturity. J Perinatol 1996;16:176–80.[Medline]

11. Anceschi MM, Piazze Garnica JJ, Rizzo G, Di Pirro G, Maranghi L, Cosmi EV. Density of amniotic fluid lamellar bodies: a comparison with classical methods for the assessment of fetal lung maturity. Prenat Neonat Med 1996;1:343–48.

12. Garite TJ, Freeman RK, Nageotte MP. Fetal maturity cascade: a rapid and cost-effective method for fetal lung maturity testing. Obstet Gynecol 1986;67:619–22.[Medline]

13. Herbert WNP, Chapman JF. Clinical and economical considerations associated with testing for fetal lung maturity. Am J Obstet Gynecol 1986;155:820–3.[Medline]

14. Tsao FHC, Zachman RD. Use of quantitative amniotic fluid phoshatidylglycerol as a criterion for fetal lung maturation. Am J Perinatol 1992;9:34–7.[Medline]

15. Olson EB, Gravenn SN, Zachman RD. Amniotic fluid lecithin to sphingomyelin ratio of 3.5 and fetal pulmonary maturity. Pediat Res 1975;9:65–9.[Medline]

16. Lauria MR, Dombrowski MP, Delaney-Black V, Bottoms SF. Lung maturity tests: relation to source, clarity, gestation age, and neonatal outcome. J Reprod Med 1996;41:685–91.[Medline]

17. American College of Obstetricians and Gynecologists. Assessment of fetal lung maturity. ACOG technical bulletin no. 230. Washington, DC: American College of Obstetricians and Gynecologists, 1996.




This article has been cited by other articles:


Home page
 Clin. Chem.Home page
A. Szallasi, A. M. Gronowski, and C. S. Eby
Lamellar Body Count in Amniotic Fluid: A Comparative Study of Four Different Hematology Analyzers
Clin. Chem., June 1, 2003; 49(6): 994 - 997.
[Full Text] [PDF]

Home page
 Clin. Chem.Home page
C. R. Fantz, C. Powell, B. Karon, C. A. Parvin, K. Hankins, M. Dayal, Y. Sadovsky, V. Johari, F. S. Apple, and A. M. Gronowski
Assessment of the Diagnostic Accuracy of the TDx-FLM II to Predict Fetal Lung Maturity
Clin. Chem., May 1, 2002; 48(5): 761 - 765.
[Abstract] [Full Text] [PDF]

Home page
 Obstet GynecolHome page
M. G. NEERHOF, E. I. HANEY, R. K. SILVER, E. R. ASHWOOD, I.-S. LEE, and J. J. PIAZZE
Lamellar Body Counts Compared With Traditional Phospholipid Analysis as an Assay for Evaluating Fetal Lung Maturity
Obstet. Gynecol., February 1, 2001; 97(2): 305 - 309.
[Abstract] [Full Text] [PDF]

Home page
 Obstet GynecolHome page
M. G. Neerhof, J. C. Dohnal, E. R. Ashwood, I.-S. Lee, and M. M. Anceschi
LAMELLAR BODY COUNTS: A CONSENSUS ON PROTOCOL
Obstet. Gynecol., February 1, 2001; 97(2): 318 - 320.
[Abstract] [Full Text] [PDF]

Home page
 Obstet GynecolHome page
B. W. J. Mol, A. Huisjes, A. Franx, and P. S. Lewis
AMNIOTIC FLUID LAMELLAR BODY COUNT: COST-EFFECTIVE SCREENING FOR FETAL LUNG MATURITY
Obstet. Gynecol., September 1, 1999; 94(3): 481 - 482.
[Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by LEWIS, P. S.
Right arrow Articles by DOMBROWSKI, M. P.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by LEWIS, P. S.
Right arrow Articles by DOMBROWSKI, M. P.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS