Prospective validation of the bedside sonographic acute cholecystitis score in emergency department patients

Background: Acute cholecystitis can be difficult to diagnose in the emergency department (ED); no single finding can rule in or rule out the disease. A prediction score for the diagnosis of acute cholecystitis for use at the bedside would be of great value to expedite the management of patients presenting with possible acute cholecystitis. The 2013 Tokyo Guidelines is a validated method for the diagnosis of acute cholecystitis but its prognostic capability is limited. The purpose of this study was to prospectively validate the Bedside Sonographic Acute Cholecystitis (SAC) Score utilizing a combination of only historical symptoms, physical exam signs, and point-of-care ultrasound (POCUS) findings for the prediction of the diagnosis of acute cholecystitis in ED patients. Method: This was a prospective observational validation study of the Bedside SAC Score. The study was conducted at two tertiary referral academic centers in Boston, Massachusetts. From April 2016 to March 2019, adult patients (≥18 years old) with suspected acute cholecystitis were enrolled via convenience sampling and underwent a physical exam and a focused biliary POCUS in the ED. Three symptoms and signs (post-prandial symptoms, RUQ tenderness, and Murphy's sign) and two sonographic findings (gallbladder wall thickening and the presence of gallstones) were combined to calculate the Bedside Sonographic Acute Cholecystitis (SAC) Score. The final diagnosis of acute cholecystitis was determined from chart review or patient follow-up up to 30 days after the initial assessment. In patients who underwent operative intervention, surgical pathology was used to confirm the diagnosis of acute cholecystitis. Sensitivity, specificity, PPV and NPV of the Bedside SAC Score were calculated for various cut off points. Results: 153 patients were included in the analysis. Using a previously defined cutoff of ≥ 4, the Bedside SAC Score had a sensitivity of 88.9% (95% CI 73.9%–96.9%), and a specificity of 67.5% (95% CI 58.2%–75.9%). A Bedside SAC Score of < 2 had a sensitivity of 100% (95% CI 90.3%–100%) and specificity of 35% (95% CI 26.5%–44.4%). A Bedside SAC Score of ≥ 7 had a sensitivity of 44.4% (95% CI 27.9%–61.9%) and specificity of 95.7% (95% CI 90.3%–98.6%). Conclusion: A bedside prediction score for the diagnosis of acute cholecystitis would have great utility in the ED. The Bedside SAC Score would be most helpful as a rule out for patients with a low Bedside SAC Score < 2 (sensitivity of 100%) or as a rule in for patients with a high Bedside SAC Score ≥ 7 (specificity of 95.7%). Prospective validation with a larger study is required.