What is the sensitivity and What is the sensitivity and specificity of amniotic fluid specificity of amniotic fluid

lamellar body count in detection lamellar body count in detection of respiratory distress syndrome?of respiratory distress syndrome?

Faculdade de Medicina da Universidade do PortoAnnual Work Class 9 Adviser: Cristina Santos

IntroductionIntroductionWhat is a respiratory distress syndrome?What is a respiratory distress syndrome?

What is a test's sensitivity and specificity?What is a test's sensitivity and specificity?

Why is this meta-analysis important?Why is this meta-analysis important?

What is the aim of this study?What is the aim of this study?

What is a respiratory distress syndrome?What is a respiratory distress syndrome?

RDS: RDS: a a condition that can occur when baby is delivered before condition that can occur when baby is delivered before its lungs are fully mature or before surfactant is formed in its lungs are fully mature or before surfactant is formed in sufficient quantitiessufficient quantities*. *.

Symptoms: dyspnoea with cyanosisSymptoms: dyspnoea with cyanosis dilatation of the alae nasidilatation of the alae nasi expiratory gruntexpiratory grunt etc.etc.

Syndrome of respiratory difficulty caused by a deficiency Syndrome of respiratory difficulty caused by a deficiency of lung of lung surfactant;surfactant;

Frequent in premature infants, children of diabetic Frequent in premature infants, children of diabetic

mothers mothers and infants delivered by caesarean and infants delivered by caesarean section;section;

* http://www.plus-size-pregnancy.org/gd/gdglossary.htm

Possible treatments : extra oxygen(21%) Possible treatments : extra oxygen(21%)

CPAP (Continuous Positive Airway Pressure), CPAP (Continuous Positive Airway Pressure),

surfactantsurfactant

In last case the baby is intubated 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

What is a test's sensitivity and specificity?What is a test's sensitivity and specificity?

SensitivitySensitivity and and specificityspecificity are parameters that express are parameters that express something about the tests’ performance;something about the tests’ performance;

SensitivitySensitivity is the test ability to detect a disease when it is is the test ability to detect a disease when it is effectively present – true positives. If the babies suffer from effectively present – true positives. If the babies suffer from respiratory distress syndrome, LBC result should be positive. respiratory distress syndrome, LBC result should be positive.

SpecificitySpecificity is the test ability to detect true negative. If the is the test ability to detect true negative. If the babies are healthy, LBC result should be negative.babies are healthy, LBC result should be negative.

Why is this meta-analysis Why is this meta-analysis important?important?

RDS remains a common cause of neonatal morbidity and RDS remains a common cause of neonatal morbidity and mortality. mortality.

Consequently fetal lung maturity (FLM) testing Consequently fetal lung maturity (FLM) testing plays an plays an important role in establishing obstetric important role in establishing obstetric management management strategiesstrategies

Several biophysical and biochemical Several biophysical and biochemical laboratory tests laboratory tests were developed were developed

The most widely used are Lecithin The most widely used are Lecithin toSphingomyelin(L/S) toSphingomyelin(L/S) ratio and the quantification of ratio and the quantification of phosphatidylglycerol (PG) phosphatidylglycerol (PG) in amniotic fluidin amniotic fluid

KhazardoostKhazardoost S, S, YahyazadehYahyazadeh H, H, BornaBorna S, S, SohrabvandSohrabvand F, F, YahyazadehYahyazadeh N, N, AminiAmini E. E.; Amniotic fluid lamellar body ; Amniotic fluid lamellar body count and its sensitivity and specificity in evaluating of fetal lung maturity. J Obstet Gynaecol. 2005 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]Apr;25(3):257-9. PMID: 16147729 [PubMed - indexed for MEDLINE]

However L/S ratio and PG estimate are unavailable at several However L/S ratio and PG estimate are unavailable at several instituitions due to economic and logistics reasonsinstituitions due to economic and logistics reasons

In this context LBC might be a viable alternative In this context LBC might be a viable alternative

Lamellar bodies can easily be counted using Lamellar bodies can easily be counted using commercial commercial blood cell analysersblood cell analysers

Therefore LBC is very Therefore LBC is very quick, simple and inexpensive test test

KhazardoostKhazardoost S, S, YahyazadehYahyazadeh H, H, BornaBorna S, S, SohrabvandSohrabvand F, F, YahyazadehYahyazadeh N, N, AminiAmini E. E.; Amniotic fluid lamellar body ; Amniotic fluid lamellar body count and its sensitivity and specificity in evaluating of fetal lung maturity. J Obstet Gynaecol. 2005 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]Apr;25(3):257-9. PMID: 16147729 [PubMed - indexed for MEDLINE]

What is the aim of this study?What is the aim of this study?

The aim of our study is a The aim of our study is a meta-analysismeta-analysis of the articles that of the articles that

evaluate the evaluate the specificityspecificity and and sensitivitysensitivity of amniotic fluid of amniotic fluid

lamellar body countlamellar body count (LBC) in detection of respiratory distress (LBC) in detection of respiratory distress

syndrome (RDS), providing by this mean reliable information to syndrome (RDS), providing by this mean reliable information to

all health personnelall health personnel about this test. about this test.

Study DesignStudy Design

Meta-analysisMeta-analysis

All studies results were analyzed in order to answer the All studies results were analyzed in order to answer the question: question:

“ “What’s the specificity and sensitivity of amniotic fluid lamellar What’s the specificity and sensitivity of amniotic fluid lamellar body count in detection of respiratory distress syndrome?”body count in detection of respiratory distress syndrome?”

Work steps:Work steps:

1.1. Search for literatureSearch for literature

2.2. Use predefined Inclusion/Exclusion Criteria to select the articleUse predefined Inclusion/Exclusion Criteria to select the article

3.3. Evaluate quality of articlesEvaluate quality of articles

4.4. Extract dataExtract data

5.5. Statistical analysis of dataStatistical analysis of data

Research methods

• Database: Medline and SCOPUS

• 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

Search processSearch process

Sensitivity and SpecificitySensitivity and Specificity

Using a recommended search strategy* Using a recommended search strategy* (sensitiv*[Title/Abstract] OR sensitivity and specificity[MeSH (sensitiv*[Title/Abstract] OR sensitivity and specificity[MeSH Terms] OR diagnos*[Title/Abstract] OR diagnosis[MeSH:noexp] Terms] OR diagnos*[Title/Abstract] OR diagnosis[MeSH:noexp] OR diagnostic * [MeSH:noexp])OR diagnostic * [MeSH:noexp])

MeSH (Medical Headin Subject): sensitivity and specificity[MeSH MeSH (Medical Headin Subject): sensitivity and specificity[MeSH Terms]; diagnosis[MeSH:noexp; diagnostic* Terms]; diagnosis[MeSH:noexp; diagnostic* [MeSH:noexp][MeSH:noexp]

Search 1: N=1962714 articlesSearch 1: N=1962714 articles

Haynes RB, Wilczynski NC for the Hedges Team. Optimal search strategies for retrieving scientifically strong studies of diagnosis 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):1040from MEDLINE: analytical survey. BMJ. 2004 May 1;328(7447):1040

Medline

We attempted to find most studies We attempted to find most studies containing the following criteriacontaining the following criteria::

11.. diagnosis studies; diagnosis studies;

22.. all diagnosis studies related to respiratory distress syndrome in newborn all diagnosis studies related to respiratory distress syndrome in newborn (RDS) a.k.a. “(hyaline membrane disease”), directly related to lung maturity (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);(which is behind the RDS and can be, in some cases by amniocentesis);

33. . obtain diagnosis studies related to the given intervention, lamellar body obtain diagnosis studies related to the given intervention, lamellar body countcount..

QueryQuery::

(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 ("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= 42 Articles

SCOPUS

Query: “lamellar body count” AND “respiratory distress syndrome”

No other articles were found that hadn’t already been included in the Medline search.

Critics on research methodsCritics on research methods

The research was based only on The research was based only on two databasestwo databases, apart from other , apart from other

data source such as Cochrane central or manual research.data source such as Cochrane central or manual research.

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

Title and abstract review

Full text review

• 2 independent reviewers

Inclusion criteriaInclusion criteria

Studies’ inclusion was processed by the selection of articles Studies’ inclusion was processed by the selection of articles that evaluated that evaluated sensitivitysensitivity and and specificityspecificity of diagnosis of diagnosis method of method of amniotic fluidamniotic fluid lamellar body countlamellar body count, in the , in the detection of detection of Respiratory Distress Syndrome. Respiratory Distress Syndrome.

The articles included were written in the following languages The articles included were written in the following languages known by the revisers: English, French, Spanish and known by the revisers: English, French, Spanish and Portuguese.Portuguese.

Exclusion criteriaExclusion criteria

In a second stage of analysis, articles were excluded according to In a second stage of analysis, articles were excluded according to the following criteria:the following criteria:

compare different techniques not referring to lamellar body count compare different techniques not referring to lamellar body count tests; tests;

include the results of lamellar body count along with the results of include the results of lamellar body count along with the results of other tests, becoming impossible to calculate the sensitivity and other tests, becoming impossible to calculate the sensitivity and specificity of the test;specificity of the test;

omit the results namely the sensitivity and specificity of lamellar omit the results namely the sensitivity and specificity of lamellar body count. body count.

Quality analysis of the studiesQuality analysis of the studies

In a third stage the selected articles were analysed by two independent revisers In a third stage the selected articles were analysed by two independent revisers in order to evaluate their quality using in order to evaluate their quality using STARD checklistSTARD checklist [3], used for [3], used for evaluation of diagnostic studies.evaluation of diagnostic studies.

To everyTo every affirmative affirmative topic was given topic was given 1 point1 point and to and to negative negative ones ones zero zero pointspoints..

The evaluation of quality was based on the sum of points resultant from article The evaluation of quality was based on the sum of points resultant from article analysis, within a analysis, within a maximum of 25 pointsmaximum of 25 points per article. per article.

Articles quality was compared using the Articles quality was compared using the meanmean of the of the two reviserstwo revisers results. results.

[3] Towards complete and accurate reporting of studies of diagnostic accuracy: the STARD initiative. The Standards for Reporting of Diagnostic [3] Towards complete and accurate reporting of studies of diagnostic accuracy: the STARD initiative. The Standards for Reporting of Diagnostic Accuracy Group.Accuracy Group.Croat Med J. 2003 Oct;44(5):635-8Croat Med J. 2003 Oct;44(5):635-8..

Data extractionData extraction

Article IDArticle ID True Positives, True Negatives; False positives; False negativesTrue Positives, True Negatives; False positives; False negatives Values of: Values of:

Sensitivity Sensitivity SpecificitySpecificity

Cut-off pointsCut-off points

Statistical analysis...Statistical analysis... ...of the agreement between ...of the agreement between reviewersreviewers in title, abstract -> in title, abstract ->

Kappa Cohen testKappa Cohen test ...of the agreement between ...of the agreement between reviewersreviewers in full text review-> in full text review->

Kappa Cohen testKappa Cohen test ......of the agreement in quality measure -> of the agreement in quality measure -> ICCICC (continuous (continuous

scale)scale) Software used: Software used: SPSS 14.0SPSS 14.0

*Devillé, Walter et all - Conducting systematic reviews of diagnostic studies - Didactic guidelines; BMC Medical *Devillé, Walter et all - Conducting systematic reviews of diagnostic studies - Didactic guidelines; BMC Medical Research Methodology 2002, 2:9Research Methodology 2002, 2:9

Data analysis:Data analysis:

Software used: Software used: MetaDiSc 1.2MetaDiSc 1.2

ResultsResults

42 42 articlesarticlesA

bst

ract

revie

w

14 included

28 excluded

3 are meta-analysis. One for comparison, the other 2 don’t mention what is pretended

7 don’t mention neither sensitivity nor specificity

16 don’t refer lamellar body count

1 has insufficient data

1 doesn’t refer the use of this method in detection of this disease

Full text review

4 not found

3 excluded

7 included for meta-analysis

AgreementAgreement

Cohen-Kappa in title and abstract evaluation: Cohen-Kappa in title and abstract evaluation:

Cohen-Kappa full-text evaluation: Cohen-Kappa full-text evaluation: 1.0001.000

Based on the conclusions of Landis and Koch (1977), we may Based on the conclusions of Landis and Koch (1977), we may classify these agreements as good.classify these agreements as good.

1st vs 2nd - 0,618

1st vs 3rd - 0,777

2nd vs 3rd - 0,727

Quality evaluationQuality evaluation

ICC = ICC = 0.7870.787

Mean quality: Mean quality: 1515

Lower value: Lower value: 1111

Highest value: Highest value: 2222

Sensitivity and Specificity table

Sensitivity and Specificity

Author Cut-off Sen [95% Conf. Iterval.] Spef [95% Conf. Iterval.]Quality

(mean)

Khazardoost [2] 50000 0,85 0,62-0,97 0,70 0,57-0,81 17.5

Beinlich [22] 30000 0,82 0.63-0.94 1,00 0,94-1,00 15

Ghidini [21] 37000 0,94 0.71-1.00 0,64 0,52-0,74 15

DeRoche [20] 37000 0,82 0.63-0.94 1,00 0,94-1,00 15

Dalence [19]30000 1.00 0.79-1.00 0,64 0,54-0,73

2210000 0.75 0.48-0.93 0,95 0,90 - 0,98

Ross [16]

41500 0.91 0.77-0.97 0,88 0,79- 0,94

19.532000 0.91 0.77-0.97 0,85 0,76-0,92

24000 0.79 0.63-0.90 1,00 0,96-1,00

21000 0.71 0.55-0.84 1,00 0,96 -1,00

Aal [23]

15000 0,78 0,56 - 0,93 1,00 0,93-1,00

1118000 0,78 0,56 - 0,93 1,00 0,93-1,00

41000 1,00 0,85 - 1,00 0,86 0,73-0,94

50000 1,00 0,85 - 1,00 0,74 0,60-0,85

Cut-off = 30000

• Heterogeneity present on both Heterogeneity present on both sensitivitysensitivity and and specificity specificity (p<0.05)(p<0.05)

• Why? Difference on qualityWhy? Difference on quality

• Dalence et al : 22Dalence et al : 22• Beilinch et al : 15Beilinch et al : 15

Cut-off= 37000

• Heterogeneity present on specificity (p<0.05)

• Homogeneity present on sensitivity (p= 0.227)

Pooled sensitivity= 0.87

Possible factors…

• Cut-off point

• Quality of the article

• Blood presence (amniocentesis)

• Vaginal mucus

• Equipment

• Confounding factors Ex:Transient tachypnea

Cut-off=50000

• Heterogeneity present on Sensitivity (p<0.05)

Difference on quality: Khazardoost – 17.5 Aal - 11

• Homogeneity present on Specificity (p=0.642)

Pooled Specificity=0.72

According to a Protocol*:

• Cut-off points under 15000/µL Higher Specificity

• Cut-off points bigger than 50000/µL Higher Sensitivity

* Neerhoof MG, Dohnal JC, Ashwood ER, Lee IS, Anceschi MM. Lamellar body counts: a consensus on protocol. Obstet Gynecol.2001 Feb; 97(2):318-20

Specificity: 0.947-1.000

Sensitivity:0.850-1.000

SROC curve

Conclusions

Some study Limitations:

• Not all the articles were found; • Different cut-off points;

• Presence of heterogeneity on the sample.

Differences in the experimental protocol lead to different results*Differences in the experimental protocol lead to different results*

Lack of similar cut-offs make statistical analysis difficult*Lack of similar cut-offs make statistical analysis difficult*

Materials used affect resultsMaterials used affect results∞∞

*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

• Cut-off point=37000 pooled sensitivity=0.87

• Cut-off point=50000 pooled specificity=0.72

• Lamellar body count is:

QuickSimpleInexpensiveGood diagnosis test