When to stop the search for an elusive source of gastrointestinal bleeding

Background and study aims: This analysis investigates the clinical parameters that should drive decisions about when to continue or stop the search for an elusive source of gastrointestinal bleeding.

Patients and methods: The number of endoscopies necessary to find a source of bleeding was estimated using the geometric distribution. A threshold analysis was used to develop a stop rule for the search for a site of bleeding. Bayes’ formula served to estimate changes in the probability of achieving a diagnosis associated with a series of consecutive endoscopic tests.

Results: With decreasing probability of diagnostic success associated with an individual endoscopic procedure, such as p = 50 %, 33 %, or 25 %, the mean (standard deviation [SD]) number of procedures needed to find the source of bleeding increases to 2 (1.41), 3 (2.45), or 4 (3.46), respectively. The threshold analysis suggests that work-up should be discontinued if the expected rise in diagnostic probability does not exceed the ratio of work-up cost to bleeding cost, that is, Δp < work-up cost/bleeding cost. For instance, a 10-fold higher cost of bleeding than endoscopy would justify continued work-up if it can improve diagnostic probability by 10 %. Bayesian analysis shows that after three negative tests the diagnostic probability drops below such a threshold.

Conclusions: The analysis suggests the following basic rules. The search for a site of gastrointestinal bleeding will take on average 2 procedures with a range of 1 – 4. The search should be continued as long as the diagnostic probability is expected to rise by more than 10 %, which is unlikely after three consecutive negative tests.

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