Evidence-based paediatrics


Chapter 39

Evidence-based paediatrics



Bob Phillips, Peter Cartledge


Learning objectives


By the end of this chapter the reader should:



Introduction


Evidence-based medicine (EBM) has now established itself as a key principle at the heart of modern clinical life. But what is it? In this chapter we will look at the principles of evidence-based medicine and how to practise it.


When we make a clinical decision (e.g. should I give this wheezy child a nebulized or spaced β2 agonist?), we need to think about the patient and the overall outcome. There could be beneficial outcomes, but these should be weighed against the possibility of negative effects. As clinicians, we instinctively assess the chances of these outcomes, weigh them, and conclude on a course of action. If we are treating a child with an acute exacerbation of asthma, we may want to know what is the best mode of delivery for a β2 agonist? But what does best mean? Patient satisfaction? Ease of delivery? Fewer symptoms? Fewest side effects? Fewer admissions? Most cost-effective? Least expensive?


For the clinician, the process of practising EBM can be difficult, time consuming, and (dare we say it) boring. In this chapter, these barriers will be tackled with examples of EBM in practice, revealing that the five minutes spent thinking this through may have saved you hours of work whilst improving the care provided to your patients.



What is EBM?


EBM was defined by one of the founders of the EBM movement, David Sackett, as ‘the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients’. But what does that mean in real terms? EBM is a shorthand term for five linked ideas:



Some misconceptions about EBM are listed in Box 39.1.




Why practise EBM?


Altruistic reasons for practising EBM


Practicing EBM improves patient care. There really should be no other incentive. Considering this in terms of the four pillars of medical ethics can be helpful:





Meeting our information needs


There are 11 new systematic reviews and 75 new trials published every day (Bastian 2010). It is impossible to keep up-to-date with all medical advancements, so long-term professional strategies are required to meet our learning and information needs.



‘Just in case’ information


Reading this book is an example of just in case information: packing in a range of general nuggets to provide a good underlying understanding of paediatrics in order to be good clinicians. When taken to the extreme, it is the diligent, regular reading of a series of journals ‘just in case’ a particular case was to present. This is inefficient and induces guilt when you cannot manage it.



‘Just in time’ information


This is a lifelong skill – the acquisition of information ‘just’ as you need it, e.g. reading a patient’s clinic notes before they arrive. In the EBM context, it is identifying information that will help us best manage our patients by seeking rapid answers to specific queries. Research has shown that a doctor in training will have two unanswered questions for every three patients they consult (Green et al 2000). An inquisitive clinician could have many more questions. As our clinical experience improves, this number is unlikely to change, but the content may become more focused.



The five steps of EBM


The practice of EBM is a multi-step process. Each of these steps (Table 39.1) requires individual skills and practice, though some resources will allow us to shortcut some of these steps. Throughout this chapter, there are examples of the ‘five steps’ in practice (see also Tables 39.3, 39.4, 39.6 and 39.9).




Step 1: Asking a question


It is all too easy to practise medicine without asking questions, as asking questions exposes potentially embarrassing gaps in our knowledge. The first step of EBM is to address this challenge and admit ignorance or uncertainty, then convert our information needs into answerable questions. This means having an inquisitive mind. Looking at the anatomy of enquiry, ask initially ‘What sort of question am I asking?’ If it is a clinical question then it can be grossly categorized as ‘foreground’ or ‘background’. Background questions are broad, and are often ‘what is’ or ‘what causes’ type questions, e.g. ‘What causes asthma in childhood?’ Foreground questions are specific and pointed, and can be fitted into a ‘PICO’ framework (patient-problem, intervention, comparison, outcome). This art is known as ‘framing a clear question’ and is an essential skill. A well-framed question must be directly related to the patient and structured in order to search for a relevant and precise answer.




Step 2: Acquiring information/evidence


The aim of this step is the acquisition of good quality information/evidence to answer your skilfully constructed question. This can be difficult, but with practice and a few tips on where to look, it gets easier. The process therefore follows three steps:



Getting your search right is both an art and a science. A good search is both sensitive and specific. A sensitive search will not miss any relevant papers, a specific search will not have too many irrelevant articles.




Where to search


There is probably no correct answer to the question, ‘where is best to search?’ You are likely to find databases which you are more comfortable using. Trip®, the Cochrane library® or PubMed® are good databases to be familiar with (Box 39.3).




Hierarchical searches

A hierarchical search aims to look for the best quality evidence first, and then work downwards if insufficient research is discovered (Fig. 39.2). If you are searching in a clinical environment, a database such as Trip® will often find results quickly (Table 39.3) and present them in evidence type. If this fails, the Cochrane library and DARE website should be searched (Table 39.4). If this does not yield any results, then PubMed’s ‘Clinical Queries’ is the next best port of call followed by a search for primary resources in PubMed.




Table 39.3


Best evidence topic (BET) – treatment









Treatment – acute exacerbation of asthma

Scenario: A 6-year-old child is admitted with a moderate exacerbation of asthma. He has been given a nebulizer of salbutamol in the A&E department and needs admission for a trial of inhaler and holding chamber (spacer). You wonder if he could have been given the inhaler in the A&E and the child sent home sooner?


Step 1: Asking a question (PICO): In a child with a moderate exacerbation of asthma [patient], is inhaled, spaced, salbutamol [intervention] as effective as nebulized [comparison] β2 agonist in terms of time to resolution of symptoms, likelihood of admission and deterioration [outcomes]?


Step 2: Acquiring evidence:


Search terms: Asthma AND spacer AND nebulizer.


Databases: Trip database – 110 results. Best result – Cochrane review.


Step 3: Appraising the evidence:





















Study group Intervention Study type Outcomes Key results Comments
2295 children in 27 trials from emergency and community setting. Any β2 agonist given by any nebulizer versus the same β2 agonist given by metered-dose inhaler with any spacer.

Cochrane systematic review.


Only RCTs considered for review.

Primary outcomes: Admission to hospital or duration of stay.


Secondary outcomes: Duration in emergency department, change in respiratory rate, blood gases, pulse rate, tremor, symptom score, lung function, use of steroids, relapse rates.

 Meta-analysis of probably heterogeneous results. Spacer versus nebulizer relative risk of admission was 0.72 (95% CI: 0.47 to 1.09). In children, length of stay in the emergency department was shorter with spacer, mean difference of −0.53 hours (95% CI: −0.62 to −0.44 hours).

Clear primary and secondary outcome measures.


Particular emphasis on the allocation concealment, which in general appears poor in most papers.


Commentary:


Acute exacerbation of asthma is common in both hospital and primary care. The airways are narrowed due to mucosal oedema, hypersecretion and bronchospasm. β2 agonists have been used successfully to relieve the bronchospasm. This paper included RCTs including adults and children. It can be argued that adults and children differ in their ability to use the devices being tested. Therefore, the results for adults and children were separated for each outcome.


In this systematic review it was found that the method of delivery of β2 agonist did not appear to affect hospital admission rates but did significantly reduce the duration of stay in the emergency department.


Step 4: Applying the evidence (the clinical bottom line):




image


Reference:


Cates CJ, et al. Holding chambers (spacers) versus nebulizers for beta-agonist treatment of acute asthma. Cochrane Database Syst Rev 2006;(2):CD000052.



Table 39.4


Best evidence topic (BET) – diagnosis









Diagnosis – cyanotic heart disease

Scenario: You start at a new hospital where you undertake ‘postnatal checks’ on newborn infants. You notice that in this hospital you do not need to perform post-ductal pulse oximetry testing. You discuss this with your consultant, who asks you to find out more exact details on the benefits of this.


Step 1: Asking a question (PICO): In an asymptomatic newborn infant [patient], does post-ductal pulse oximetry [intervention] increase the number of infants correctly identified with congenital heart disease or reduce mortality rates [outcomes]?


Step 2: Acquiring evidence:


Search terms: (Infant, newborn OR infant* OR newborn OR ‘newborn infant’ OR neonat*) AND (heart defects, congenital OR congenital heart defect* OR Defect*, congenital heart OR heart, malformation of OR heart abnormalit* OR congenital heart disease OR cyanotic heart disease OR cyanotic heart defect OR congenital heart malformation) AND (oximetry OR oximetry, pulse OR blood gas monitoring, transcutaneous OR oximetry, transcutaneous OR oximetry, transcutaneous OR saturation*, oxygen OR oxygen saturation*)


Databases: Cochrane: 164 results, 4 non-Cochrane reviews including below meta-analysis.


Step 3: Appraising the evidence:





















Study group Intervention Study type Outcomes Key results Comments

13 eligible studies with data for 229,421 asymptomatic newborn babies.


118 infants with critical congenital heart defects. 748 false positives. 33 false negatives.

Pulse oximetry.


60% of studies used foot alone (postductal).

 Systematic review and meta-analysis of 12 cohort and 1 case-control study. Detection of critical congenital heart defects.

Sensitivity 76.5% (95% CI 67.7–83.5), specificity was 99.9% (99.7–99.9), false positive rate 0.14 (0.06–0.33).


Likelihood ratio positive 549 (238–1195), likelihood ratio negative 0.24 (0.17–0.33).


Lower false positive rate if oximetry >24 hours (p=0.0017), but no effect on sensitivity.

Clear description of search strategy.


No statistical description of heterogeneity.


Significant publication bias was reported.


Commentary:


Screening for critical congenital heart defects in newborn babies can aid early recognition, with the prospect of improved outcome. In this case, the new doctor was not interested in an individual patient but a population. As the search had the potential to lead to widespread change in the clinical assessment of all newborns, the search for evidence needed to identify the most relevant and highest quality available. The search was therefore very comprehensive.


Though this systematic review found that pulse oximetry is highly specific for critical congenital heart disease, it does not look at broader outcomes. For example, do infants who have their diagnosis made earlier using screening have better long-term outcomes (e.g. mortality)? This would be an important consideration when balancing the cost (equipment, time, etc.) of implementing such a screening tool.


Step 4: Applying the evidence (the clinical bottom line):


Get Clinical Tree app for offline access