Investigations

The most helpful tests for H. pylori are: 

• CLO test ^c
• histology looking for antral inflammation ^c and H. pylori bacteria ^a
• urease breath test ^{a b c}
• ELISA ^a

 Why?

The CLO test and histology are most helpful at diagnosing H. pylori infection

Patient	Target Disorder and Reference Standard	Diagnostic Test	LR+ (95% CI)	Post-test Probability	LR- (95% CI)	Post-test Probability
suspected H. pylori infection c (pre-test probability: 65%)	H.pylori infection (4 concordant tests)	CLO test	infinity (29 to infinity)	100%	0.10 (0.067 to 0.16)	16%
		acute antral inflammation	0.14 (6.2 to 30)	96%	14 (0.097 to 0.21)	21%
		chronic antral inflammation	3.0 (2.2 to 3.9)	84%	0.0 (0.0 to 0.026)	0%
		Warthin-Starry stain	88 (13 to 620)	99%	0.07 (0.041 to 0.12)	11%
suspected H. pylori infection a (pre-test probability: 48%)	H.pylori infection (histology)	Giemsa stain	25 (3.6 to 170)	96%	0.043 (0.0064 to 0.30)	4%
dyspepsia and suspected H. pylori infection a (pre-test probability: 35%)	H.pylori infection (histology + CLO test)	urease breath test	14 (6.2 to 30)	88%	0.091 (0.036 to 0.23)	5%
suspected H. pylori infection c (pre-test probability: 65%)	H.pylori infection (4 concordant tests)	serum IgG	11 (5.6 to 21)	95%	0.095 (0.058 to 0.15)	15%
		serum IgA	4.8 (3.0 to 7.9)	90%	0.34 (0.26 to 0.43)	38%
undergoing upper GI endoscopy c (pre-test probability: 62%)	H.pylori infection (2 positive from histology, culture, rapid urease breath test)	stool immunoassay	12 (4.9 to 32)	92%	0.043 (0.011 to 0.17)	4%
dyspepsia and suspected H. pylori infection a (pre-test probability: 35%)	H.pylori infection (histology + CLO test)	ELISA	9.3 (5.0 to 17)	83%	0.071 (0.024 to 0.21)	4%