A critical analysis of a paper about pre

A critical analysis of a paper about pre-school wheeze : 

A critical analysis of a paper about pre-school wheeze Frank et al, BMJ 336:1423 21 August 2008 Learner Set Samir Dawlatly (VTS SHO)

Aims and Objectives of Analysis : 

Aims and Objectives of Analysis Are the results valid? (VALIDITY) What are the results? (RELIABILITY) Will the results help locally (APPLICABILITY)

Study methods : 

Study methods 5 postal surveys in Manchester 1993, 1995, 1999, 2001, 2004 2 general practice populations Sent to parents/guardians of all children 4 cohorts 1993 to 2004 - 1995 to 2004 1993 to 2001 - 1995 to 2001 Details of survey in previous paper BJGP 2005;55:596-602 – but not fully described!

Questions asked : 

Questions asked Gender Does child have wheeze? Family history of asthma? History of hay fever or eczema? Questions about various predictors See Table 3

Results : 

Results Children categorised as following: 26.8% of those with wheeze at baseline had persistent asthma Had data for 2 surveys on 628 children (49%)

Prognostic factors : 

Prognostic factors History of atopic disorders Exercise induced wheeze NOT > 3 attacks Woken by wheeze Speech affected Age Gender Family history

Author’s conclusions : 

Author’s conclusions ¼ of those with wheeze before age 5 will develop persistent asthma If child has exercise-induced wheeze or atopy they are about 4 times more likely to develop asthma But only half of those with wheeze and both risk factors develop asthma

Author’s evaluation : 

Author’s evaluation Potential measurement error introducing bias Decrease likelihood by using 4 identical surveys Selection bias reduced by using whole population No important differences in baseline data between those included and those not

My evaluation : 

My evaluation What happened to 1999 survey? Study not designed for answering question in paper Gathered a whole bunch of data and tried to find something significant? 49% inclusion rate is poor – but good comparison of those included to those not (Table 2) Reasonable response rate to survey But what about responder bias? Stats seem sound – but very wide CI’s

More of my questions : 

More of my questions Author’s use parental definition of wheeze, hay fever and eczema Is this accurate? Other studies dispute this Limited population – single area of Manchester ?ethnicity ?social composition Influence of Big Pharma Astra Zeneca Allen & Hanbury’s (Glaxo subsidiary)

Conclusions : 

Conclusions VALIDITY Flawed methodology with potential biases RELIABILITY Seems to make sense biologically – atopy theory Consistent with other studies APPLICABILITY Inclusive, pragmatic style study – ?applicable to general practice population But can the Wythenshawe population be generalised?

How will it affect my practice? : 

How will it affect my practice? When I see a wheezy under 5… “All that wheezes is not asthma” “Research has shown that only 1 in 4 of those with wheeze will go on to develop asthma” “It’s important to know if they get wheezy after exercise…” “Your child is more likely to develop asthma if they have hay fever or eczema...” “Even if your child has hay fever/eczema there’s still only a 50% chance they will develop asthma”

Thank you : 

Thank you Any questions or comments?