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Three Part Question

In [adults presenting to the ED with a skin and soft tissue infection (SSTIs)], does [bedside ultrasound compared to physical examination] improve [the diagnostic accuracy for detecting abscess requiring drainage]?

Clinical Scenario

While working the evening shift, a 45 year-old man presents to the emergency department with a progressive erythematous and swelling area on his leg. He is afebrile with unremarkable vital signs. The physical exam is suspicious for underlying abscess, as there is a fluctuant and localized pain. Before you proceed to drainage, you wonder if a bedside ultrasound of the soft tissue might help you to better assess the presence or absence of abscess to avoid unnecessary procedure.

Search Strategy

Search made on october 22th 2017
A) No BestBETs or critical appraisals were found on this topic.

B) The website www.clinicaltrials.gov was searched for ongoing trials on the subject.
One trial was found on the subject: Liebmann O., Soft Tissue Ultrasound of Infections, Identifier: NCT01557426, Rhode Island Hospital. The study has been completed but is not published yet.

C) The Cochrane Library was searched for reviews on the subject. No reviews were found.

D) MEDLINE using the PubMed interface (1950 – 2017/10/22)
#1 – (((sonography OR echography OR ultrasound OR POCUS OR point of care ultrasound)[ti, ab]) OR (ultrasonography[MeSH Terms])) = 488,532 papers
#2 – (abscess OR skin soft tissue infection OR SSTI OR cellulitis)[ti, ab]= 61,829 papers
#3 – ((emergency room OR emergency department OR ED)[ti, ab]) = 104,239 papers
#4 – #1 AND #2 AND #3 = 135 papers

A total of 135 papers were found, of which 128 were irrelevant after the reading of titles/abstract. Studies that examined intraoral, peritonsillar, breast, perineum and deep neck space abscess were excluded. After this titles/abstract screening: 7 papers were left for reviewing. After reviewing the articles: 3 papers were found which answered the question.

E) EMBASE using the Elsevier interface (1945 – 2017/10/22)
#1 – (sonography OR echography OR ultrasound OR POCUS OR point of care ultrasound OR ultrasonography )[ti, ab] =413,642 articles
#2 – (abscess OR skin soft tissue infection OR SSTI OR cellulitis)[ti, ab]= 74,872 articles
#3 – ((emergency room OR emergency department OR ED)[ti, ab]) = 193,916 articles
#4 – #1 AND #2 AND #3 = 295 articles
A total of 295 papers were found, of which 287 were irrelevant after the reading of titles/abstract. 7 papers were left for reviewing. After reviewing the articles, 3 relevant papers were found, but they were the same 3 duplicates from those found on Medline, adding no additional paper.

F) Google Scholar, Journal Club and the grey literature were search, but did not highlight any additional papers.

Search Outcome

325 papers were found (excluding duplicates). After reviewing the articles, 322 papers were excluded as they were found irrelevant to the question, or they were paediatric population. Two systematic reviews have been found, one in 2016 (Subramamiam, et al., 2016) and another one updated in 2017 (Barbic., et al., 2017) including both paediatric and adults studies, which were not retained because of the different population included. A total of 3 relevant papers were retained in this review, which are summarized in the table 1.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Squire, T., et al. July 2005 California, USA	All adult patient presenting to the ED with a chief complaint suggesting cellulitis or superficial abscess (N=107).	Prospective clinical trial	Primary outcome: true abscess : pus on I+D or failure to resolve symptoms at 7 days if lesion not drained Secondary outcome: How often POCUS changed diagnosis to the correct one.	Sn physical exam (P/E): 86% (CI: 76-93%) vs P/E +POCUS 98% (CI: 93-100%) Sp (P/E): 70% (CI: 55-82%) vs P/E +POCUS 88% (CI: 76-96%). PPV (P/E): 81% (CI: 70-90%) vs P/E +POCUS 93% (CI: 84-97%). NPV (P/E) :77% (CI: 62-88%) vs P/E +POCUS 97% (CI: 88-100%). Use of POCUS changed the clinical dx in 17% of cases (18/107), in which the dx was correct in 17/18 (94%).	Single center, convenience sample Two reference standard (pus on drainage and favourable evolution for cellulitis) Unknown number of ED doctors and resident that performed the POCUS. Not blinded (POCUS performed by treating physicians). Unknown quality insurance of obtained POCUS. 27 patients lost to follow-up, on which 25 were excluded from the final analysis.
Tayal, V., et al., 2006 NC, USA	Patients ?18 years with evidence of cutaneous soft-tissue infection and no signs of evidence of obvious abscess in the judgment of the treating ED physicians (n=126)	Prospective observational study.	Primary outcome: effect of POCUS on management of the clinical cellulitis by the treating physician. Secondary outcome: effect of POCUS on management stratified by pretest probability for abscess presence.	POCUS changed the management of 56% (71/126) patients with clinical cellulitis. POCUS had a management effect in all pretest probabilities of abscess from 10% to 90%. Pretest group believed no drainage needed: (n=82), POCUS changed the management in 48% (39/82, CI: 37%-58%) with 33 positive drainages and 6 further diagnostics or consultation. Pretest group believed drainage needed (n=44), POCUS changed the management in 73% (32/44, CIß 58%-85%), including 16 eliminated drainages with favourable evolution at 72h and 16 patients with modification of their drainage or further imaging/consultations.	Single center, convenience sample Unknown quality insurance of obtained POCUS. Two reference standard (pus on drainage and favourable evolution for cellulitis) Lack of clear inclusion/exclusion criteria may have led to selection bias (obvious abscess in the judgment of the treating physician where excluded). Unclear and subjective criterion standard for changed management: avoided drainage and drainage technique modification (deep, location incision modifications). Only 72h patient follow up for not drained infection.
Berger, T., et al., 2012 NY, USA	Adult patients with suspicion of abscess and plan to incise and drain (n= 40).	Prospective observational study.	Primary outcome: positive pus on I+D.	Sn P/E 76% (CI: 58-89%) vs POCUS 97% (CI: 83-100%). Sp (P/E): 83% (CI: 36-99%) vs POCUS 67% (CI: 24-94%). Positive LR: (P/E): 4.5 vs POCUS 2.9 Negative LR: (P/E): 0.29 vs POCUS 0.04 Area under ROC: (P/E): 0.75 vs POCUS 0.85 (p=0,06). Not statistically significant.	Single center, lack of power due to small sample size, convenience sample Unknown quality insurance of obtained POCUS. Unknown number of ED doctors and resident that performed the POCUS. Only patients with suspected abscess have been included. Follow up of the patient evolution was not part of the reference standard (6 patients drained without abscess on drainage).

Comment(s)

Although all of these three prospective observational studies have selection bias and limitations, the findings suggest that bedside ultrasound utilization when managing SSTI may improve diagnosis accuracy for detecting abscess. Only two studies evaluated the diagnostic accuracy as primary outcome, where POCUS alone or combined to physical exam had higher sensitivity (97-98%) at detecting abscess requiring drainage compare to the physical examination alone (76-86%). However, conflicting data were obtained concerning specificity. One study had improved specificity (88% using POCUS alone or combined to physical exam compared to physical exam (70%), however, the study of Berger et al., 2012 had reduced specificity to identify abscess (67% compared to physical exam (88%)), but the study lacked of power due to small sample size and only included patients with suspected abscess by the treating physician. When looked at the changed physician management after performed POCUS, two studies obtained results ranging from 17% to 56% of the cases consequently to the wide definition of what is considered a changed management. Therefore, future research on this subject is needed to validate those findings to multiple clinical sites. Also, in order to eliminate the double reference standard, further studies should compare POCUS findings to formal ultrasound realized by radiologist as standard criterion.

Editor Comment

POCUS: point of care ultrasound

Clinical Bottom Line

In adult presenting to the ED with skin and soft tissue infection, the use of bedside ultrasound may provide a superior accuracy to diagnose underlying abscess compared to standard physical examination.

Level of Evidence

Level 3 - Small numbers of small studies or great heterogeneity or very different population.

References

1. Squire, B., Fox, C., Anderson, C ABSCESS: Applied Bedside Sonography for Convenient Evaluation of Superficial Soft Tissue Infections. Acad Emerg Med Vol.12, No.7.
2. Tayal V., Hasan, N., Norton, J., Tomaszewski, C., The Effect of Soft-tissue Ultrasound on the Management of Cellulitis in the Emergent Department Society for Academic Emergency Medicine April 2006, Vol 13, No 4.
3. Berger T., Garrido, F., Green, J., Lema, P., Gupta, J. Bedside ultrasound performed by novices for the detection of abscess in ED patients with soft tissue infections American Journal of Emergency Medicine 2012, 30, 1569-1573.