11
Concerns
• This test should not be performed in patients with severe uncontrolled hypertension,
renal insufficiency, cardiac arrhythmia, or severe hypokalemia.
• 24-h urine collection may be inconvenient. Laboratory-specific poor performance of the
RIA for urinary aldosterone (aldosterone 18- oxo-glucuronide or acid labile metabolite)
may blunt diagnostic accuracy—a problem obviated by the currently available HPLC-
tandem mass spectrometry methodology.
• Aldosterone 18-oxo-glucuronide is a renal metabolite, and its excretion may not rise in
patients with renal disease.
This test should not be performed in patients with severe uncontrolled hypertension,
renal insufficiency, cardiac arrhythmia, or severe hypokalemia.
• Although some centers conduct this test in the outpatient setting (provided that
patients are able to attend frequently to monitor their potassium), in other centers
several days of hospitalization are customary.
• Most of the data available come from the Brisbane group who have established, on the
basis of a very large series of patients, a cutoff of a PAC of 6 ng/dL (170 nmol/L) at 10
AM in an ambulatory patient on day 4.
• Proponents of the FST argue that: a) it is the most sensitive for confirming PA; b) it is
a less intrusive method of sodium loading than SIT and therefore less likely to provoke
non-renin-dependent alterations of aldosterone levels; c) it allows for the potentially
confounding effects of potassium to be controlled, and for ACTH (via cortisol) to be
monitored and detected; and d) it is safe when performed by experienced hands.
