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Faculdade de Medicina da Universidade do Porto Turma 9

What is the sensitivity and specificity of amniotic fluid lamellar body count in detection of respiratory distress syndrome?. Faculdade de Medicina da Universidade do Porto Turma 9. Introduction.

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Faculdade de Medicina da Universidade do Porto Turma 9

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  1. What is the sensitivity and specificity of amniotic fluid lamellar body count in detection of respiratory distress syndrome? Faculdade de Medicina da Universidade do Porto Turma 9

  2. Introduction What is the aim of this study?What is a respiratory distress syndrome?What is a test's sensitivity and specificity? Why is this meta-analysis important?

  3. What is the aim of this study? • The aim of our study is a meta-analysis of the articles that evaluate the specificity and sensitivity of amniotic fluid lamellar body count (LBC) in detection of respiratory distress syndrome (RDS), providing by this mean reliable information to all health personnel about this test.

  4. What is a respiratory distress syndrome? • RDS: Frequent in premature infants, children of diabetic mothers and infants delivered by caesarean section; Syndrome of respiratory difficulty caused by a deficiency of lung surfactant; Symptoms: dyspnoea with cyanosis dilatation of the alae nasi expiratory grunt etc.

  5. Possible treatments : extra oxygen(21%) CPAP (Continuous Positive Airway Pressure), surfactant In last case the baby is intubated CUNNINGHAM, F.Gary et al ;William’s Obstetrics;22nd edition; Mc Graw-Hill; Medical Publishing Division; New York www.pedriatics.wisc.edu

  6. RDS remains a common cause of neonatal morbidity and mortality. Consequently fetal lung maturity (FLM) testing plays an important role in establishing obstetric management strategies several biophysical and biochemical laboratory tests were developed the most widely used are Lecithin toSphingomyelin (L/S) ratio and the quantification of phosphatidylglycerol (PG) in amniotic fluid Khazardoost S, Yahyazadeh H, Borna S, Sohrabvand F, Yahyazadeh N, Amini E.; Amniotic fluid lamellar body count and its sensitivity and specificity in evaluating of fetal lung maturity. J Obstet Gynaecol. 2005 Apr;25(3):257-9. PMID: 16147729 [PubMed - indexed for MEDLINE]

  7. However L/S ratio and PG estimate are unavailable at several instituitions due to economic and logistics reasons in this context LBC might be a viable alternative lamellar bodies can easily be counted using commercial blood cell analysers therefore LBC is very quick, simple and inexpensive test Khazardoost S, Yahyazadeh H, Borna S, Sohrabvand F, Yahyazadeh N, Amini E.; Amniotic fluid lamellar body count and its sensitivity and specificity in evaluating of fetal lung maturity. J Obstet Gynaecol. 2005 Apr;25(3):257-9. PMID: 16147729 [PubMed - indexed for MEDLINE]

  8. Several studies have shown lamellar body counts to be accurate predictors of fetal lung maturity (Greenspoon et al 1995) • Recently, it was demonstrated that the LBC could reduce by approximately three-quarters the need for L/S assays (Lewis et al 1999)

  9. What is a test's sensitivity and specificity? • Sensitivity and specificity are parameters that express something about the tests’ performance; • Sensitivity is the test ability to detect a disease when it is effectively present – true positives. If the babies suffer from respiratory distress syndrome, LBC result should be positive. • Specificity is the test ability to detect true negative. If the babies are healthy, LBC result should be negative. Search on Wickipedia for sensitivity and specificity.

  10. Why is this meta-analysis important? Problem: There is some doubt about the sensitivity and specificity of LBC in determination of RDS So... This meta-analysis allows the analysis of all articles about this topic on Pubmed till October 2005 and it answers the question: “What is the sensitivity and specificity of amniotic fluid lamellar body count in detection of respiratory distress syndrome?”

  11. Study Design • Systematic review with meta-analysis, whenever aggregation of articles by cut-off values was possible. • All studies results and differences on the conclusions were analyzed in order to answer the question: “What’s the specificity and sensitivity of amniotic fluid lamellar body count in detection of respiratory distress syndrome?”

  12. Steps of article: • Search for literature • Use predefined Inclusion/Exclusion Criteria to select the article • Evaluate quality of articles • Extract data • Statistical analysis of data

  13. Research methods • Database: Medline • Limits: publications until 2005/10; Humans • The search aimed at finding the most evidence which could be useful in estimating the sensitivity and specificity of lamellar body count from the amniotic fluid in detection of respiratory distress syndrome in Newborn

  14. Search Plan • Objective:find articles related to diagnostic studies referring to the respiratory distress syndrome. 1.Find articles of all diagnostic studies 2.Find articles of all diagnostic studies referring to amniotic fluid 3.Find articles of all diagnostic studies referring respiratory distress syndrome, Newborn 4.Find articles of all diagnostic studies related to lamellar body count 5.Gather all data

  15. Search process • Sensitivity and Specificity Using a recommended search strategy* (sensitiv*[Title/Abstract] OR sensitivity and specificity[MeSH Terms] OR diagnos*[Title/Abstract] OR diagnosis[MeSH:noexp] OR diagnostic * [MeSH:noexp]) MeSH (Medical Headin Subject): sensitivity and specificity[MeSH Terms] ; diagnosis[MeSH:noexp ; diagnostic * [MeSH:noexp] Search 1: N=1962714 articles Haynes RB, Wilczynski NC for the Hedges Team. Optimal search strategies for retrieving scientifically strong studies of diagnosis from MEDLINE: analytical survey. BMJ. 2004 May 1;328(7447):1040

  16. We attempted to find most studies containing the following criteria: 1.diagnosis studies related to amniotic fluid 2. all diagnosis studies related to respiratory distress syndrome in newborn (RDS) a.k.a. “(hyaline membrane disease”), directly related to lung maturity (which is behind the RDS and can be, in some cases by amniocentesis). 3. obtain diagnosis studies related to the given intervention, lamellar body count, Query: (sensitiv*[Title/Abstract] OR sensitivity and specificity[MeSH Terms] OR diagnos*[Title/Abstract] OR diagnosis[MeSH:noexp] OR diagnostic * [MeSH:noexp] OR diagnosis,differential[MeSH:noexp] OR diagnosis[Subheading:noexp]) AND ("amniotic fluid" [MeSH]) AND ("respiratory distress syndrome, Newborn" [MeSH] OR "lung maturity" OR "respiratory distress syndrome" OR "FLM" OR “surfactant” OR “hyaline membrane”) AND ("lamellar body count" OR "lamellar bodies" ) N=25 articles

  17. Due to the restrict number of articles found required another search on SCOPUS, using the query: “Lamellar body count” AND “Respiratory distress syndrome” No other articles were found that were not included in the medline search.

  18. Critics on research methods The research was based only on two databases, apart from other data source such as Cochrane central or manual research and final Medline research query may have been too specific[2]. Pai M, McCullock M, Gorman JD, Pai N, Enanoria W, Kennedy G, Tharyan P, Colford JM Jr. Systematic reviews and meta-analyses: Na illustrated, step-by-step guide. The National Medical Journal of India 2004; 17(2): 86-95

  19. Title and abstract review • 3 independent reviewers read the titles and abstract selecting them according to the inclusion/exclusion criteria.

  20. Inclusion criteria Studies’ inclusion was processed by the selection of articles that evaluated sensitivity and specificity of diagnostic method of amniotic fluid lamellar body count, in the detection of Respiratory Distress Syndrome. • The articles included were written in the following languages known by the revisers: English, French, Spanish and Portuguese. With the application of previously defined inclusion criteria, 14 articles were considered valid.

  21. Exclusion criteria In a second stage of analysis, articles were excluded according to the following criteria: • compare different techniques not referring to lamellar body count tests; • include the results of lamellar body count along with the results of other tests, becoming impossible to calculate the sensitivity and specificity of the test; • omit the results namely the sensitivity and specificity of lamellar body count.

  22. Quality analysis of the studies • In a third stage the selected articles were analysed by two independent revisers in order to evaluate their quality using STARD checklist [3], used for evaluation of diagnostic studies. • To every affirmative topic was given 1 point and to negative ones zero points. • The evaluation of quality was based on the sum of points resultant from article analysis, within a maximum of 25 points per article. • All of the 6 selected studies held the fundamental requirements to proceed to its inclusion in a meta-analysis. • Articles quality was compared using the mean of the two revisers results. [3] Towards complete and accurate reporting of studies of diagnostic accuracy: the STARD initiative. The Standards for Reporting of Diagnostic Accuracy Group.Croat Med J. 2003 Oct;44(5):635-8.

  23. Characteristics of participants • According to the article aim, the units of analysis were all the diagnosis studies included based on the methods previously defined.

  24. Data extraction • True Positives, True Negatives; False positives; False negatives • Article ID • Values of: • Sensitivity • Specificity • Cut-off points • Outcome Variable • Confidence Interval (95%) • Software used for input and analysis: Metadisc 1.2

  25. Statistical analysis • The agreement in title, abstract and full text review -> Kappa Cohen test • Agreement in quality measure -> ICC • Software used: SPSS 13.0 Data analysis*: • Presentation of the results of individual studies • Searching for the presence of heterogeneity • Testing of the presence of an (implicit) cut-point effect • Dealing with heterogeneity • Deciding which model should be used if statistical pooling is appropriate • Statistical pooling Software used: MetaDiSc 1.2 *Devillé, Walter et all - Conducting systematic reviews of diagnostic studies - Didactic guidelines; BMC Medical Research Methodology 2002, 2:9

  26. Results

  27. From the 13 articles selected from title and abstract review 9 full-text were obtained 6 articles were included in the metanalysis

  28. Agreement • The agreement evaluation test for the title, abstract and full-text review was performed using Cohen Kappa agreement test-1960 to study this property between the choices of different revisers. • Cohen-Kappa in title and abstract evaluation: 0.818 • Full-text evaluation: 1.000 • Based on the conclusions of Landis and Koch(1977), we may classify these agreements as good.

  29. Quality evaluation • ICC=0.72 • Mean quality: 16.25 • Lower value:15 • Highest value:22

  30. Sensitivity table

  31. Sensitivity graphic Homogeneous sensitivity independent from cut-off value.

  32. Specificity table

  33. Specificity graphic • Many factors affect specificity:* • Blood presence; • Vaginal mucus; • Transient trachypnea There are groups with similar specificity->Subgroup analysis *Neerhof MG, Dohnal JC, Ashwood ER, Lee IS, Anceschi MM. Lamellar body counts: a consensus on protocol. Obstet Gynecol. 2001 Feb; 97(2):318-20.

  34. Cut-off point=30000 • Heterogeneity present • Why? Difference on quality • Dalence et al : 22 • Beilinch et al : 15

  35. Sensitivity graphic

  36. Specificity graphic

  37. Cut-off point=37000 • Heterogeneity present in specificity and homogeneity in sensitivity

  38. Cut-off 30000-50000 and similar counters • Very homogeneous • Why? Maybe similar counters • Counter used in Dalence: Coulter STKR/ Coulter S + IV (both were calibrated)/ Sysmex 780 (not user modifiable) • Counter used in khazardoost: Coulter STKR • Counter used in ghidini: Coulter STKR

  39. Conclusion • Diferences in the experimental protocol lead to different results * • Lack of simillar cut-offs make statistical analysis difficult * • Materials used affect results+ • For any cutoff, the sensibility is high ->Great screening test *Neerhof MG, Dohnal JC, Ashwood ER, Lee IS, Anceschi MM. Lamellar body counts: a consensus on protocol. Obstet Gynecol. 2001 Feb; 97(2):318-20. +Bowie LJ, Shammo J. Lamellar body number density and the prediction of respiratorydistress syndrome. Am J Clin Pathol 1991; 95:781-6

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