Table 2.

Causes of reduced BIPSS performance.

False negative	False positive
Cyclic or mild CD	Cyclic EAS
Low responsiveness to CRH stimulation of corticotrophic tumor	Cortisol-lowering treatment in EAS
Corticotrophic tumor ectopically located in sphenoidal sinus	Very low peripheral ACTH levels
	CRH producing ectopic tumors