Investigations

• Urea, electrolytes and glucose ^{b c}  

Why?

A low potassium makes primary hyperaldosteronism more likely

Patient	Target Disorder and Reference Standard	Diagnostic Test	LR+ (95% CI)	Post-test Probability	LR- (95% CI)	Post-test Probability
suspected primary hyperaldosteronism c (pre-test probability: 0.6%)	primary hyperaldosteronism (biochemistry and imaging studies)	potassium < 4.0 mmol/l	24 (9.2 to 63)	13%	0.035 (0.0089 to 0.14)	0.021%

Note:

• Primary hyperaldosteronism can occur with a normal potassium: 2.7% of cases in one study (95% CI: 0.0% to 6.4%) ^c