Table 1.

Summary of the characteristics of the 37 studies fulfilling the inclusion criteria.

Characteristic	Studies (n)	(%)
Study design
Prospective case series	9	(24)
Retrospective case series	19	(51)
Diagnostic case–control (two-gate series)	4	(11)
Design unclear	5	(14)
Population characteristics
Sample size (participants)	*50.4	†(12–181)
Sample size (lesions)	*52.3	†(14–146)
Prevalence of malignancy (%)	*38.1	†(13–74)
Mean age (years; 29 studies)	‡*55.8	†(44.1–66.7)
Female participants (%; 31 studies)	*49.4	†(6–87)
Mean tumor size (mm; 24 studies)	‡*41.9	†(22–68.1)
Mean % symptomatic participants (5 studies)	*36	†(26–47)
Confirmed hormone excess (%; 11 studies)	*36.3	†(0.02–88)
Index tests and thresholds
CT	16	(43)
Non-enhanced tumor density	13	(35)
Contrast-enhanced washout studies	6	(16)
MRI	15	(41)
Chemical shift loss of signal intensity	8	(22)
Adrenal to liver ratio signal intensity	8	(22)
Adrenal to spleen ratio signal intensity	5	(14)
Adrenal to muscle ratio signal intensity	2	(5)
PET	4	(11)
SUVmax	3	(8)
SUVmax adrenal to liver ratio	5	(14)
PET-CT	5	(14)
SUVmax	3	(8)
ALR SUVmax	4	(11)
Population grouping for analysis
Initial finding incidental in ≥90% included participants	3	(8)
Initial finding incidental in 50–90% included participants	4	(11)
Initial indication for imaging due to known cancer in ≥90% included participants	9	(24)
Initial indication for imaging due to known cancer in 50–90% included participants	2	(5)
Initial finding incidental in <50% OR <50% imaging indication known cancer	2	(5)
Population composition not reported	17	(46)
Reference standard
Histology alone	16	(43)
Histology and imaging follow-up	15	(41)
Histology and imaging follow-up, plus other reference	5	(14)
Histology plus other reference	1	(3)

SUV_max, maximum standardized uptake value; ALR SUV_max, ratio of SUV_max in the adrenal gland compared with the liver.

^*Mean;

^†Range;

^‡Mean of reported means.