Clinical ultrasound is safe and highly specific for acute appendicitis in moderate to high pre-test probability patients

Daniel Corson-Knowles, Frances Russell

Research output: Contribution to journalArticle

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Abstract

Introduction: Clinical ultrasound (CUS) is highly specific for the diagnosis of acute appendicitis but is operator-dependent. The goal of this study was to determine if a heterogeneous group of emergency physicians (EP) could diagnose acute appendicitis on CUS in patients with a moderate to high pre-test probability. Methods: This was a prospective, observational study of a convenience sample of adult and pediatric patients with suspected appendicitis. Sonographers received a structured, 20-minute CUS training on appendicitis prior to patient enrollment. The presence of a dilated (>6 mm diameter), non-compressible, blind-ending tubular structure was considered a positive study. Non-visualization or indeterminate studies were considered negative. We collected pre-test probability of acute appendicitis based on a 10-point visual analog scale (moderate to high was defined as >3), and confidence in CUS interpretation. The primary objective was measured by comparing CUS findings to surgical pathology and one week follow-up. Results: We enrolled 105 patients; 76 had moderate to high pre-test probability. Of these, 24 were children. The rate of appendicitis was 36.8% in those with moderate to high pre-test probability. CUS were recorded by 33 different EPs. The sensitivity, specificity, and positive and negative likelihood ratios of EP-performed CUS in patients with moderate to high pre-test probability were 42.8% (95% confidence interval [CI] [25-62.5%]), 97.9% (95% CI [87.5-99.8%]), 20.7 (95% CI [2.8-149.9]) and 0.58 (95% CI [0.42-0.8]), respectively. The 16 false negative scans were all interpreted as indeterminate. There was one false positive CUS diagnosis; however, the sonographer reported low confidence of 2/10. Conclusion: A heterogeneous group of EP sonographers can safely identify acute appendicitis with high specificity in patients with moderate to high pre-test probability. This data adds support for surgical consultation without further imaging beyond CUS in the appropriate clinical setting. [West J Emerg Med. 2018;19(3)460–464.]

Original languageEnglish (US)
Pages (from-to)460-464
Number of pages5
JournalWestern Journal of Emergency Medicine
Volume19
Issue number3
DOIs
StatePublished - May 1 2018

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Appendicitis
Confidence Intervals
Emergencies
Physicians
Surgical Pathology
Visual Analog Scale
Observational Studies
Referral and Consultation
Prospective Studies
Pediatrics
Sensitivity and Specificity

ASJC Scopus subject areas

  • Emergency Medicine

Cite this

Clinical ultrasound is safe and highly specific for acute appendicitis in moderate to high pre-test probability patients. / Corson-Knowles, Daniel; Russell, Frances.

In: Western Journal of Emergency Medicine, Vol. 19, No. 3, 01.05.2018, p. 460-464.

Research output: Contribution to journalArticle

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abstract = "Introduction: Clinical ultrasound (CUS) is highly specific for the diagnosis of acute appendicitis but is operator-dependent. The goal of this study was to determine if a heterogeneous group of emergency physicians (EP) could diagnose acute appendicitis on CUS in patients with a moderate to high pre-test probability. Methods: This was a prospective, observational study of a convenience sample of adult and pediatric patients with suspected appendicitis. Sonographers received a structured, 20-minute CUS training on appendicitis prior to patient enrollment. The presence of a dilated (>6 mm diameter), non-compressible, blind-ending tubular structure was considered a positive study. Non-visualization or indeterminate studies were considered negative. We collected pre-test probability of acute appendicitis based on a 10-point visual analog scale (moderate to high was defined as >3), and confidence in CUS interpretation. The primary objective was measured by comparing CUS findings to surgical pathology and one week follow-up. Results: We enrolled 105 patients; 76 had moderate to high pre-test probability. Of these, 24 were children. The rate of appendicitis was 36.8{\%} in those with moderate to high pre-test probability. CUS were recorded by 33 different EPs. The sensitivity, specificity, and positive and negative likelihood ratios of EP-performed CUS in patients with moderate to high pre-test probability were 42.8{\%} (95{\%} confidence interval [CI] [25-62.5{\%}]), 97.9{\%} (95{\%} CI [87.5-99.8{\%}]), 20.7 (95{\%} CI [2.8-149.9]) and 0.58 (95{\%} CI [0.42-0.8]), respectively. The 16 false negative scans were all interpreted as indeterminate. There was one false positive CUS diagnosis; however, the sonographer reported low confidence of 2/10. Conclusion: A heterogeneous group of EP sonographers can safely identify acute appendicitis with high specificity in patients with moderate to high pre-test probability. This data adds support for surgical consultation without further imaging beyond CUS in the appropriate clinical setting. [West J Emerg Med. 2018;19(3)460–464.]",
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