Investigations

• urea, electrolytes and creatinine ^a

Note:

A urea: creatinine ratio ≥ 100 can help diagnose an upper gastrointestinal bleed

Patient	Target Disorder and Reference Standard	Diagnostic Test	LR+ (95% CI)	Post-test Probability	LR- (95% CI)	Post-test Probability
suspected upper GI bleed a (pre-test probability: 74%)	upper GI bleed (endoscopy or barium studies)	urea: creatinine ratio ≥ 100 (SI units)	4.4 (1.5 to 13)	93%	0.41 (0.27 to 0.61)	54%

• A larger ratio indicates a greater bleed. ^a