What is the sensitivity of a computed tomography (CT) scan for diagnosing appendicitis?

From the Guidelines

The sensitivity of a computed tomography (CT) scan for diagnosing appendicitis is approximately 95%. This high sensitivity is based on a recent meta-analysis of 71 study populations, which reported a summary sensitivity of 0.95 (95% CI: 0.93-0.96) for CT in the diagnosis of appendicitis 1. CT scans are highly effective diagnostic tools for suspected appendicitis, providing excellent visualization of the appendix and surrounding structures. The use of CT for adult emergency department visits for diagnosis of appendicitis has increased significantly over the years, and it is now considered the most useful diagnostic imaging modality for evaluating patients with suspected appendicitis 1.

When performed with intravenous contrast, CT scans can detect appendiceal inflammation, wall thickening, appendicolith (stone in the appendix), and complications such as perforation or abscess formation. The high sensitivity means CT scans rarely miss cases of appendicitis, though specificity is also important (around 94-97%), indicating few false positives 1. Some key factors that can affect the sensitivity of CT scans for appendicitis diagnosis include:

• The use of contrast, with contrast-enhanced CT having a higher sensitivity compared to unenhanced CT 1
• Scanner technology, with newer scanners providing better image quality and higher sensitivity 1
• Radiologist experience, with more experienced radiologists providing more accurate interpretations 1
• Timing of the scan relative to symptom onset, with earlier scans providing better sensitivity 1

CT scanning has become the standard imaging modality for evaluating suspected appendicitis in most adult patients, particularly when the clinical presentation is atypical or unclear. However, radiation exposure remains a concern, especially in children and pregnant women, where ultrasound is often used as the initial imaging study. The accuracy of CT for appendicitis diagnosis can be affected by various factors, but overall, it remains a highly effective and reliable diagnostic tool.

From the Research

CT Scan Sensitivity for Appendicitis

• The sensitivity of a computed tomography (CT) scan for diagnosing appendicitis is high, with a summary sensitivity of 0.95 (95% confidence interval 0.93 to 0.96) 2.
• A study comparing CT with intravenous contrast alone to CT with intravenous and oral contrast found that both had 100% sensitivity for appendicitis 3.
• Another study reported a sensitivity of 90% and a specificity of 89% for CT scans in diagnosing acute appendicitis 4.
• The use of intravenous contrast material improved the diagnostic accuracy of helical CT for acute appendicitis, with a sensitivity of 92.9% and a specificity of 93.7% 5.
• A comparative assessment of CT and sonographic techniques found that CT examinations had higher sensitivity and specificity than sonography, with sensitivities ranging from 72% to 80% and specificities ranging from 86% to 91% 6.

Factors Affecting CT Scan Sensitivity

• The use of contrast enhancement, such as intravenous or oral contrast, can affect the sensitivity of CT scans for appendicitis 2, 3, 5.
• The type of CT scanner and the experience of the radiologist can also influence the diagnostic accuracy of CT scans 2.
• The sensitivity of CT scans can vary depending on the population being studied and the criteria used to diagnose appendicitis 2, 4, 6.

Clinical Implications

• CT scans can be a useful diagnostic tool for appendicitis, particularly in cases where the diagnosis is uncertain 2, 3, 4.
• The high sensitivity and specificity of CT scans make them a valuable tool for confirming or ruling out appendicitis 2, 3, 5, 6.
• However, the results of CT scans should be interpreted in the context of clinical findings and other diagnostic tests 2, 4, 6.