What is the most sensitive test for diagnosing gastrointestinal (GI) bleeding?

From the Guidelines

The most sensitive test for diagnosing gastrointestinal bleeding is video capsule endoscopy (VCE), with a diagnostic yield of 50-72% in patients with obscure overt GI bleeding, and up to 87-91.9% when performed within 48 hours of presentation with bleeding. This is based on the evidence from a study published in 2019 in the journal Gut 1. VCE is a non-invasive investigation that permits examination of the entire length of the small bowel in 79-90% of patients, and is increasingly used in patients presenting with overt-obscure GI bleeding who have had negative adequate upper and lower GI endoscopy.

The sensitivity of other tests, such as CT angiography (CTA) and nuclear medicine, is lower, with CTA having a reported sensitivity of 79-95% and a specificity of 95-100% in retrospective clinical studies of LGIB 1. Nuclear medicine, such as radionuclide imaging, has a highly variable accuracy rate for localizing bleeding, ranging from 24 to 91% 1.

In terms of prioritizing tests, VCE should be considered as the first-line investigation for patients with suspected GI bleeding, particularly those with obscure overt GI bleeding, as it has the highest diagnostic yield and is non-invasive. However, the choice of test may depend on the individual patient's presentation and the availability of resources.

Some key points to consider when using VCE include:

• The diagnostic yield of VCE is highest when it is performed as close as possible to the bleeding episode
• VCE should be performed within 48 hours of presentation with bleeding for optimal results
• VCE is particularly useful in patients with obscure overt GI bleeding who have had negative adequate upper and lower GI endoscopy
• The results of VCE should be interpreted in conjunction with other diagnostic tests, such as CTA and nuclear medicine, to determine the cause and location of GI bleeding.

From the Research

Diagnostic Tests for Gastrointestinal Bleeding

The most sensitive test for diagnosing gastrointestinal (GI) bleeding is a topic of interest in the medical field.

• Endoscopy is considered the criterion standard for the detection of a source of GI bleeding, with a study showing that it identified bleeding lesions in 67% of patients with an initial negative CT angiography 2.
• CT angiography has been found to have poor sensitivity for identification of a GI bleeding source or lesion, with a sensitivity of 20% compared to endoscopy 2.
• Other radiologic techniques, such as catheter angiography, computed tomography enterography, magnetic resonance enterography, nuclear medicine red blood cell scan, and technetium-99m pertechnetate scintigraphy (Meckel scan), are also used to evaluate patients with GI bleeding, but their sensitivity and specificity vary 3.
• Laboratory tests, such as complete blood count, basic metabolic panel, coagulation panel, liver tests, and type and crossmatch, are also important in the evaluation of GI bleeding 4.
• The Glasgow-Blatchford bleeding score is a clinical prediction guide used for upper GI bleeding risk stratification and to determine therapy 4.
• Blood urea nitrogen (BUN) level has been found to be significantly higher in patients with upper GI bleeding compared to those with lower GI bleeding, with a threshold value of 21.0 mg/dL having a specificity of 93.0% for distinguishing upper from lower GI bleeding 5.

Comparison of Diagnostic Tests

• Endoscopy is generally considered the most sensitive test for diagnosing GI bleeding, especially for upper GI bleeding 2, 4.
• CT angiography is less sensitive than endoscopy, but may be useful in certain situations, such as when endoscopy is not available or feasible 2, 3.
• Other diagnostic tests, such as laboratory tests and clinical prediction guides, are also important in the evaluation of GI bleeding, but their sensitivity and specificity vary 4, 5.