Tag Archives: trauma

Talking Heads: S100B For Detection of Intracranial Injury in Mild Head Trauma in Children

Where can I find this paper?

http://www.ncbi.nlm.nih.gov/pubmed/26283067

What is this paper about (what is the research question)?

Does S100B, a calcium-binding protein located in the cytoplasm and nucleus of astrocytes and Schwann cells, have a role in predicting intracranial injury (or its absence) for mild head trauma in children?

Summary of the Paper

Design: multicentre prospective cohort study

Objective: to determine the test characteristics for S100B in mild head trauma in children with determination of a cutoff to provide diagnostic utility.

Outcome of interest: diagnostic/predictive performance of S100B biomarker for intracranial injury in children with mild head trauma

Reference Standard: presence of intracranial injury (any collection of blood within the cranial vault or cerebral oedema) on CT scan

Participants: children aged <16 years presenting to one of three Swiss paediatric EDs between January 2009 and December 2011

Inclusions: patients with mild head injury (acute head trauma with confusion or LOC <30mins or amnesia or transient neurological abnormality) for whom a CT was performed and blood obtained for S100B assay.
Exclusions: children arriving >6h after head trauma, children with Down syndrome, patients with a history of seizure in the preceding 28/7

Results: 80 children were enrolled of whom 73 were included in the analysis. 20 (27.4%) had evidence of intracranial injury on CT although none required surgical intervention.

The area under the Receiver Operator Characteristic (ROC) curve for S100B was 0.73 (95% CI 0.60-0.86) which improved to 0.77 (95% CI 0.65-0.89) when under 2s were excluded.

Using a cutoff of 0.14micrograms/L gave a sensitivity of 95% (95% CI 77%-100%) for all children [100% (95% CI 81%-100%) with under 2s excluded] and specificity 34.0% (95% CI 27%-36%).

Authors’ Conclusions:

The biomarker S100B is a valuable tool to help the physician decide whether head CT is indicated for children aged <16 years with mild head trauma. Its excellent sensitivity indicates that it could be an accurate tool to “rule out” an intracranial injury.

On the study design

This was a small prospective study in which blood samples were taken from children presenting with mild head injury deemed by clinicians to require CT scan and analysed independently of the CT findings to permit calculation of test characteristics for the biomarker S100B.

The authors included patients under 16 presenting to one of three Swiss paediatric EDs with mild head injury (acute head trauma with confusion or LOC <30mins or amnesia or transient neurological abnormality) for whom a CT was requested; these subjects also had a venous blood sample for S100B level which was not available before CTs had been reported. They then determined test characteristics for S100B in the context of CT findings. The sample size was pretty small – 80 children were enrolled of whom 7 were excluded, either because they didn’t have the blood test at all, within 6h or they didn’t have the CT scan. This affects the applicability of the study.

Performing bloods on children in the ED is a tricky one; children with major trauma presentations frequently have blood tests taken but these children might not. It’s worth considering how many additional blood tests we might be performing if S100B is adopted into everyday practice.

The other interesting thing is the classification of “mild head injury”. These children were selected because they were having CT head (the reference standard for determining the presence or absence of intracranial injury) but the population does not completely correlate with those head injured children who would have a CT indicated according to the NICE head injury guidelines – which is going to affect whether we can directly extrapolate the results to our ED head injured population as there may be some children we would want to CT who would not have been included in this study.

What were the results and what does this mean?

Only 73/80 were included in the analysis, of whom 20 had an intracranial injury. No surgical interventions were required in any case so we may be missing this proportion of severely head injured patients which, combined with the inclusion of only “mild head injuries” means that we have really only looked at a slice of our PED head injury population.

The ROC curve for S100B had an AUC of 0.73 (95% CI 0.60-0.86) which improved to 0.77 (95% CI 0.65-0.89) when under 2s were excluded.

Using a cutoff of 0.14micrograms/L gave a sensitivity of 95% (95% CI 77%-100%) for all children (100% (95% CI 81%-100%) with under 2s excluded) and specificity 34.0% (95% CI 27%-36%). This looks good, but look at the width of those confidence intervals, reflective of the small sample size. If the true sensitivity is 77% that’s no good at all – so we definitely need confirmation with a bigger study and ideally wider inclusion, so we can apply the findings to all our head injured patients.

What can we take from this paper into clinical practice?

There’s definitely potential for S100B to be used as a lesser evil compared with radiation exposure on the developing brain. However the evidence (and, in all likelihood, the assays in your laboratory) isn’t there yet. Watch this space… I suspect there is more to come on S100B.

More questions to ask

How would S100B perform for all head injured children in a bigger study?
Do we need to exclude the under-2s to improve test characteristics – and what should we do with those children?
What is the level of sensitivity we will accept at the cost of specificity?

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Clinician Suspicion in Blunt Torso Trauma – Place Your Bets

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Where can I find this paper?

http://www.ncbi.nlm.nih.gov/pubmed/26302354

What is this paper about (what is the research question)?

Are clinicians better at predicting intra-abdominal injuries in children with blunt torso trauma than a derived clinical prediction rule?

Summary of the Paper

Design: Secondary analysis of some existing PECARN group data from a prospective cohort study of children with blunt torso trauma

Objective: to compare the test characteristics of clinician suspicion with a derived clinical prediction rule to identify children at very low risk of intra-abdominal injuries undergoing acute intervention

Outcome: test characteristics for clinician suspicion, measured against presence or absence of need for acute intervention for intra-abdominal injury.

Comparison: test characteristics of a derived clinical prediction rule from the same population.

Participants: 12044 patients recruited between May 2007-January 2010 and eligible to participate in the parent study (http://www.ncbi.nlm.nih.gov/pubmed/23375510) underwent secondary analysis.

Inclusions: children <18 years old with blunt torso trauma presenting to participating PECARN Emergency Departments
Exclusions: injury >24h prior to attendance; pre-existing neurological disorders affecting examination findings; pregnancy; transfer from another institution.

Results:

3016/9252 deemed low risk (<1%) for clinician suspicion had CT abdomen performed; 35 patients subsequently had acute intervention. Of the remaining patients with clinician suspicion ≥1%, 168/2667 had an acute intervention.

Negative clinician suspicion had the following test characteristics;

sensitivity 82.8% (95% CI 77.0-87.3)
specificity 78.7% (95% CI 77.9-79.4%)
NPV 99.6 (95% CI 99.5-99.7%)
LR- 0.2 (95% CI 0.2-0.3)

Low risk on the prediction rule had the following test characteristics;

sensitivity 97.0% (95% CI 93.7-98.6)
specificity 42.5% (95% CI 41.6-43.4%)
NPV 99.9 (95% CI 99.7-99.9%)
LR- 0.1 (95% CI 0.0-0.2)

Authors’ conclusions

A clinical prediction rule had a significantly higher sensitivity for identifying intra-abdominal injury undergoing acute intervention, but a lower specificity. The higher specificity of clinician suspicion did not translate into clinical practice as clinicians frequently obtained abdominal CT scans in patients they considered to be at very low risk.

On the study design

This was a secondary analysis of data collected as part of an original PECARN study on abdominal trauma in children. It’s always worth remembering that while secondary analysis can reveal some very useful information and trends, this was not the original purpose for which the study group was recruited or the study powered (although the authors tell us this study was preplanned, and the standardised data collection forms used to collect information about clinician decision making supports this).

The study has an issue in that the “gold standard” abdominal CT was not applied to all patients, only those deemed to be at risk of injury. This means there is a large portion of patients who had no imaging and no intervention who may still have had intra-abdominal injury although without a need for clinical intervention the significance of this is doubtful.

Good attempts were made to follow subjects up to ensure no clinically important outcomes were omitted.

What were the results and what does this mean?

There is an important distinction in this paper between the presence of an abdominal injury and one requiring intervention (specified as death, therapeutic intervention at laparotomy, angiographic embolisation, blood transfusion for anaemia or administration of intravenous fluids for at least two nights). This composite reference standard is pragmatic but we could argue about whether intra-abdominal injuries not requiring intervention are also clinically relevant or not, considering the comparative risks of radiation exposure with abdominal CT.

It is worth noting that not all of the 12044 subjects enrolled had CT abdomen performed. 11919 were deemed to have no suspicion of injury, which we must doubt given the fact that neither clinician suspicion nor clinical prediction rule achieved 100% sensitivity.

The study found that in patients with intra-abdominal injury requiring intervention, the clinician correctly identified the risk as ≥1% in 82.8% (95% CI 77.0-87.3) of cases, and in patients who did not have intra-abdominal injury requiring intervention, the clinician correctly identified that the risk was <1% in 78.7% (95% CI 77.9-79.4%) of cases. Unfortunately this shows that clinician judgement alone is neither sensitive nor specific enough to support decision making in isolation. This is borne out in a high CT abdomen rate in the population, despite a high proportion of low risk patients.

The decision rule, which determined risk as “not low” in the presence of any one of:

no evidence of abdominal wall trauma or seat belt sign
GCS >13
no abdominal tenderness
no evidence of thoracic wall trauma
no complaints of abdominal pain
no decreased breath sounds
no history of vomiting after the injury

had better sensitivity (so the absence of these signs performs better as a predictor of the lack of need for CT and intervention) but poorer specificity (i.e. the presence of any sign does not accurately predict a need for intervention).

Of note there were three patients whose injuries were not identified by clinician prediction or derived clinical prediction rule, so neither predictor achieved 100% sensitivity.

What can we take from this paper into clinical practice?

We as clinicians rely a lot on clinical judgement but that alone is a poor predictor of the need for intervention for intra-abdominal injury, especially when compared with this non-validated derived prediction rule. Following validation the prediction rule may have some diagnostic utility, especially when combined with observation.

More questions to ask

How will this decision rule perform when validated?
How would the rule perform if the specificity of clinician judgement was incorporated?

21st November 2012: Accuracy of Point-of-Care US for Diagnosis of Elbow Fractures in Children

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**Sincere apologies for the delay in this post (due 16th Nov, delayed by technical problems)**

Where can I find this paper?

http://www.ncbi.nlm.nih.gov/pubmed/23142008

What is this paper about (what is the research question)?

How good is ultrasound at diagnosing elbow fractures in children?

Summary of the Paper

Design: prospective, observational, multi-centre diagnostic study

Objective: to determine the performance characteristics of ED ultrasound by PEM physicians for diagnosis of elbow fractures in children

Test under evaluation: ED (point-of-care) ultrasound of the elbow (scanning protocol pre-determined) to determine presence of lipohaemarthrosis OR elevated posterior fat pad

Reference standard: plain radiographs reported by radiologists blinded to ultrasound findings. Clinical follow-up with notes review or structured telephone follow-up; radiologist report used if follow-up imaging performed.

Primary outcome: determination of test characteristics

Population: convenience sample of patients aged up to 21yrs presenting to either of two urban EDs when a trained study physician was available, between Sept 2010 and Dec 2011.

Inclusion: possible elbow fracture requiring radiographic assessment
Exclusion: elbow radiographs already obtained, previous confirmed elbow fracture, open wound at the elbow, unstable vital signs, severe life threatening injuries requiring resuscitation.

Results: 130 patients enrolled, fracture present on initial ED radiography in 38/130. 5 additional fractures diagnosed on follow-up radiography (23 patients).

Elevated posterior fat pad was seen on initial XR in 57/130 patients (44%): 36 with fracture, 21 without (of whom, 4 patients had fracture identified on follow-up).

Elevated posterior fat pad OR lipohaemarthrosis was seen on ED US in 68/130 patients.

Elevated posterior fat pad OR lipohaemarthrosis gave the following test characteristics: sensitivity 98% (95% CI 88-100%), specificity 70% (95% CI 60-79%), PPV 0.62 (95% CI 0.50-0.72), NPV 0.98 (95% CI 0.91-1.0), LR+ 3.3 (95% CI 2.4-4.5), LR- 0.03 (95% CI 0.01-0.23)

Authors’ Conclusions:

With focused musculoskeletal ultrasonographic training, novice PEM sonologists were able to attain the skills necessary to perform point-of-care elbow ultrasonography to evaluate for fracture by assessing the posterior fat pad for elevation and lipohaemarthrosis.

On the study design

Despite including “children” up to the age of 21 (!), there are many positive points about the methodology in this paper. The authors involved two centres over 16 months and although the sample was obtained as a convenience sample, the wide inclusion and few exclusions mean that there’s a good chance that the population is representative of patients seen in my ED.

There are reasonable attempts to minimise bias:

Standardised training
Blinding of radiologists to US results/clinical findings
Standardised data collection sheet for clinical/examination findings
Composite reference standard (telephone follow-up)

In addition, it seems pragmatic – with only 1hr training plus 5 practice scans PEM clinicians could achieve an agreement of 0.94 with an experienced PEM sonologist! What concerns me slightly is how unclear it is who these PEM clinicians were. We can all think of the colleagues who would jump at the chance to take part in a study like this; the fact that only one sonologist had prior experience of elbow ultrasound does NOT mean that the others were inexperienced with US in general. Would these results be reproducible in the hands of a not-quite-sure-which-end-of-the-probe-goes-where EM clinician – even with an hour of training? I’m not so sure…

However, the study is nicely designed and would be relatively easy to replicate in your own department.

What were the results and what does this mean?

For diagnostic studies, it can be helpful to draw a 2×2 table. This allows the calculation of test characteristics. Below is a 2×2 table for the presence of posterior fat pad OR lipohaemarthrosis on elbow US.

		REFERENCE STANDARD
		Positive	Negative	Total
US	Positive	42	26	68
	Negative	1	61	62
	Total	43	87	130

Sensitivity of 98% is not terrible, although the 95% confidence interval (88-100%) is pretty wide. This means the “true” sensitivity of elbow US in ED could be as low as 88%. Remember, high sensitivity means that when the test is negative we can effectively rule out the disease (fracture). Would we be happy to rule out at 88%? I don’t think so.

What’s most interesting is that the LR+ for elevated posterior fat pad AND lipohaemarthrosis is 5.8; that is, the proportion of patients who have a fracture and these findings is 5.8 times the proportion of patients with these findings who do not have a fracture. We can surmise that finding both elevated PFP and LH would be highly suggestive of an underlying fracture; but would this prevent an x-ray? Unlikely (pesky orthopods)! We don’t know quite how this correlates with the degree of required intervention (were these the fractures which needed to go to theatre; that were horrible looking supracondylar fractures from the outset?). And the LR- is not particularly brilliant when we look at the confidence intervals.

Not all patients who were followed-up had repeat XRs, but this reflects clinical practice and I think it is pretty reasonable not to XR a child who is pain-free with normal range of movement at their follow-up appointment. In fact, the radiation would be hard to justify. It is worth noting that four patients could not be followed-up; all had negative US and negative XR at their initial visit and were included in the “no fracture” group. The authors made reasonable attempts to follow-up these patients; how would the results be altered if we assumed the worst for these cases? And does it matter?

What can we take from this paper into clinical practice?

With appropriate training and practice, EM clinicians could use ultrasound to reliably exclude elbow fractures in children. However, a larger study is needed to tighten those confidence intervals; further training might also have this effect.

If both lipohaemarthrosis and elevated posterior fat pad are identified on US it is very likely that there is an underlying fracture, but would this change clinical practice? Probably not – yet 🙂

More questions to ask

Would more training/greater patient numbers narrow the confidence intervals (so we can effectively rule-out elbow fracture with ultrasound)?
Would the results be reproducible with a joe-bloggs ED clinician who’s a bit wobbly with an US probe (like me)?
Could we ever persuade orthopods to manage patients on the basis of US-diagnosed fractures without corresponding radiographs?

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