Die mees algemene beskikbare toetse vir FLM sluit in: surfaktant/albumien- (SA)-
verhouding, fosfatidielgliserol (FG) teenliggaamagglutinasietoets en telling van.
THE
EXCEED EXPECTATIONS :
“Pathology that Adds Value”
PATHCARE NEWS
Update on Fetal Lung Maturity Testing The accurate prediction of fetal lung maturity (FLM) based on results from amniotic fluid samples is of utmost importance in the prevention of neonatal respiratory distress syndrome and its complications. The most commonly offered tests for FLM include: surfactant/albumin (S/A) ratio, phosphatidylglycerol (PG) antibody agglutination test and lamellar body count (LBC). Currently the S/A ratio is the most widely performed test for FLM. Abbott announced that they are retiring the S/A analytical systems worldwide, and ending the production of the reagent required to perform S/A ratios. This test will no longer be available from November 2011. The currently available FLM tests include:
Test
Lamellar Body Count (LBC)
Phosphatidylglycerol (PG)
Lamellar bodies are lamellated phospholipids that represent a storage form of surfactant. Because lamellar body diameter (range 1-5 µm) is similar to that of small platelets, LBC can be obtained rapidly with the use of the platelet channel of a haematology analyser.
PG is a minor constituent of surfactant. It begins to increase appreciably in amniotic fluid after 35 weeks of gestation, and can appear earlier in infants with accelerated lung maturity. Because PG enhances the spread of phospholipids in the alveoli, its presence indicates an advanced state of fetal lung development and function.
Principle
AmnioStat-FLM® PG test - A rapid semi-quantitative slide antibody agglutination test.
Instrument/method
Haematology analyser
Interpretation
LBC
Interpretation
PG
Interpretation
≤ 15 000 /µL
Immature FLM
Negative
Immature FLM
15 000-50 000 /µL
Borderline FLM
Low Positive
Borderline FLM
≥ 50 000 /µL
Mature FLM
Positive
Mature FLM
Interferences
Blood contamination can lead to false elevation of LBC because platelets from the blood are counted as lamellar bodies. Meconium interference is minimal.
Bacterial contamination can give a false positive PG result. PG agglutination is not affected by the presence of blood or meconium.
Sensitivity Specificity
97-98 %
95-100 %
29-35 %
9-50 %
Availability
Routinely available at all laboratories with a Haematology cell counter.
The PG agglutination test is available at selected laboratories.
Cost
± R 104
± R 280
References: 1. 2. 3. 4. 5.
Szallasi A et al. Lamellar Body Count in Amniotic Fluid: A Comparative Study of Four Different Hematology Analyzers. Clin Chem 2009; 49 (6): 994-7. Ashwood ER. Standards of laboratory practice: evaluation of fetal lung maturity. Clin Chem 1997; 43(1): 211-214. Dalence CR et al. Amniotic fluid lamellar body count: a rapid and reliable fetal lung maturity test. Obstet Gynecol 1995; 86:235. AmnioStat-FLM-PG package insert. Lafler DJ et al. Laboratory testing to assess Fetal Lung Maturity. Women Department of Pathology July 2001 32:393-396.
Compiled by: Dr Mariana Lloyd, Chemical Pathologist, PathCare
LABORATORY UPDATE
www.pathcare.co.za
November 2011
DIE
OORTREF VERWAGTINGE : “Patologie wat Waarde Toevoeg”
PATHCARE NUUS
Nuwe inligting oor Toetsing vir Fetale Longmaturiteit Die akkurate voorspelling van fetale longmaturiteit (FLM) gebaseer op die resultate van amnionvogmonsters is van die uiterste belang by die voorkoming van neonatale respiratoriese noodsindroom en sy komplikasies. Die mees algemene beskikbare toetse vir FLM sluit in: surfaktant/albumien- (SA)- verhouding, fosfatidielgliserol (FG) teenliggaamagglutinasietoets en telling van lamellêre liggampies (LLT). Tans is die S/A-verhouding die mees algemene toets vir FLM. Abbott het aangekondig dat hulle wêreldwyd die S/A- analitiese stelsels onttrek en die produksie van die reagens om die S/A-verhouding te meet, opskort. Hierdie toets sal vanaf November 2011 nie langer beskikbaar wees nie. Die huidige beskikbare FLM-toetse sluit in:
Toets
Lamellêre liggaampietelling (LLT)
Fosfatidielgliserol(FG)
Lamellêre liggampies is gelamelleerde fosfolipiede wat 'n stoorvorm van surfaktant is. Omdat hul deursnit (grense 1-5 µm) soortgelyk aan dié van klein plaatjies is, kan die LLT vinnig met gebruik van die plaatjiekanaal van 'n hematologie- analiseerder verkry word.
PG is 'n mindere komponent van surfaktant. Dit vermeerder aansienlik in amnionvog na 35 weke swangerskap en kan vroeër voorkom in babas met versnelde longontwikkeling. Omdat FG die verspreiding van fosfolipiede in die alveoli versnel, dui teenwoordigheid daarvan op 'n gevorderde stadium van fetale longontwikkeling en funksie.
Beginsel
AmnioStat-FLM® FG toets - 'n vinnige semi-kwantitatiewe teenliggaamplaatjie-agglutinasietoets
Instrument/metode
Hematologie-analiseerder
Interpretasie
LLT
Interpretasie
FG
Interpretasie
≤ 15 000 /µL
Baie jong FLM
Negatief
Baie jong FLM
15 000-50 000 /µL
Grenslyn FLM
Laag Positief
Grenslyn FLM
≥ 50 000 /µL
Volwasse FLM
Positief
Volwasse FLM
Steurings
Bloedkontaminasie kan tot vals verhoogde LLT lei want bloedplaatjies word as lamellêre liggampies getel. Versteuring deur mekonium is minimaal.
Bakteriële kontaminasie kan tot 'n vals positiewe FG-resultaat lei. FG-agglutinasie word nie deur bloed of mekonium beïnvloed nie.
Sensitiwiteit Spesifisiteit
97-98 %
95-100 %
29-35 %
9-50 %
Beskikbaarheid
Roetiene beskikbaar by alle laboratoriums met 'n hematologie-selteller.
Die FG-agglutinasietoets is by geselekteerde laboratoriums beskikbaar.
Prys
± R 104
± R 280
Verwysings: 1. 2. 3. 4. 5.
Szallasi A et al. Lamellar Body Count in Amniotic Fluid: A Comparative Study of Four Different Hematology Analyzers. Clin Chem 2009; 49 (6): 994-7. Ashwood ER. Standards of laboratory practice: evaluation of fetal lung maturity. Clin Chem 1997; 43(1): 211-214. Dalence CR et al. Amniotic fluid lamellar body count: a rapid and reliable fetal lung maturity test. Obstet Gynecol 1995; 86:235. AmnioStat-FLM-PG package insert. Lafler DJ et al. Laboratory testing to assess Fetal Lung Maturity. Women Department of Pathology July 2001 32:393-396.
Saamgestel deur: Dr Mariana Lloyd, Chemiese Patoloog, PathCare
