Objectives and hypotheses
Are the objectives of the study clearly stated?
Yes it was to determine which signs and symptoms are sensitive for haemopneumothorax. The underlying aim (not stated apriori by the investigators) is that if clinical exam is sensitive it may be used as a SnOut to prevent the need for chest Xray.
Is the study design suitable for the objectives
Yes. They have taken a cohort of patients with chest trauma, all had clinical exam, all had CXR. They then compared the results.
This is a diagnostic cohort study.
Who / what was studied?
676 patients presenting to a level 1 trauma centre in the US. 523 patients had blunt trauma. 153 had penetrating trauma. Ages ranged from 12-98 years.
Patients who were cardiovascularly unstable were excluded from the study.
Recreuitment was non sequential. It is not stated why. We cannot infer whether this was random non recruitment (unlikely to cause significant bias) or systematic (where it might - eg no recruitment when only junior staff on).
All patients had their clinical exam documented by the admitting team. The CXR was read by the trauma team. Blunt trauma patients had one Xray. Penetrating patients had 2 (another at 6 hours).
Was this the right sample to answer the objectives?
Yes it appears to represent a group of patients typical of those presenting to an ED. There is arguably a paucity of baseline information on the patients that may have helped in the interpretation of the findings.
Is the study large enough to achieve its objectives? Have sample size estimates been performed?
No sample size calculation has been performed. No confidence intervals are given for the final estimates of sensitivity etc. This suggests a lack of understanding of research design / statistical inference.
Were all subjects accounted for?
It would appear so.
Were all appropriate outcomes considered?
I think so. They are only looking for CXR abnormality and they have done that.
Has ethical approval been obtained if appropriate?
Was an independent blinded gold standard test applied to all subjects?
All patients had a CXR. It is debatable if this is a gold standard for PNX as some are only seen on CT. However, it is probably acceptable as it reflects clinical practice and occult PNXs are unlikely to be that clinicall relevant.
Measurement and observation
Is it clear what was measured, how it was measured and what the outcomes were?
No. There is little explanation of how the authors determined auscultation to be abnormal beyond the presence of bilateral breath sounds. I find this difficult to believe that this represents the abscence of breath sounds on one side and probably reflects a Difference in breath sounds. However, this is not explicitly stated and is a little confusing.
Are the measurements valid?
Yes apart from that mentioned above
Are the measurements reliable?
Are the measurements reproducible?
Presentation of results
Are the basic data adequately described?
No. Further baseline data and more explicit examination data would be useful
Are the results presented clearly, objectively and in sufficient detail to enable readers to make their own judgement?
No there is insufficuent detail regarding exam findings.
Are the results internally consistent, i.e. do the numbers add up properly?
Are the data suitable for analysis?
Are the methods appropriate to the data?
Yes but not enough!
Are any statistics correctly performed and interpreted?
Sensitivity Specificity PPV and NPV are appropriately performed
The abscence of confidence intervals is a concern. In fact you can work the confidence intervals out using an online statistical calculator e.g.http://members.aol.com/johnp71/ctab2x2.html
If you do this forn the blunt trauma patients I estimate the sensitivity is 100% BUT the confidence intervals go from 57-100%!!!!!!!!!!!
Hardly something that gives us a definitive answer/.
Are the results discussed in relation to existing knowledge on the subject and study objectives?
Is the discussion biased?
Are the authors' conclusions justified by the data?
The authors conclusions are as follows.
1. Clinical exam can rule out CXR abnormailty in blunt trauma patients (CVS stable).
- No CIs given in fact they are so wide that this paper is not definitive. However, the prevalence in this group is very low so it is unlikely that a sufficiently large trial will be performed. The study does suggest that CXR abnormality is very unlikely in these patients
2. Clinical exam cannot rule out CXR abnormality in penetrating patients (CVS stable)
- This appears to be true and we should keep doing them
What level of evidence has this paper presented? (using CEBM levels )
Does this paper help me answer my problem?
Can the test be implemented in practice?
Hmmm Not sure. The interesting thing for me is that the prevalence is low and they have found a high sensitivity (though wide CIs). Do we believe the findings. Well the outcome (normal exam + pretty normal patient + CVS stable = no CXR) probably represents current practice in many UK emergency departments anyway for blunt trauma.
Penetrating trauma is clearly a different kettle of onions.
What aids to implementation exist?
The decision to CXR could be incorporated into a protocol for ED use.
What barriers to implementation exist?
Yet another protocol!!
Are my patients the same as the patients tested?
Not absolutely clear but probably
Will the test improve diagnosis in my patients?
No this is a cost/radiation/time saving decision