Evidence-based On-call

Anaemia

Clinical features

Ask about a history of gastrectomy (for B₁₂ deficiency) ^b

or other bowel resection ^c

Why?

A history of gastrectomy makes cobalamin deficiency slightly more likely

Patient	Target Disorder and Reference Standard	Diagnostic Test	LR+ (95% CI)	Post-test Probability	LR- (95% CI)	Post-test Probability
undergoing cobalamin assay ^b (pre-test probability: 1.2%)	cobalamin deficiency (Schilling test)	history of gastrectomy	7.4 (3.2 to 17)	7%	0.54 (0.33 to 0.88)	1%