Table 2.

Quality assessment of prevalence studies included.

Author	Year	Type of Study	Strength	Limitations
Cedermark et al.[28]	1981	Retrospective observational study	• Histology proven adrenal metastases • Use of ACTH stimulation test for diagnosis with clear documentation of values. • Representative of patients with bilateral metastases	• Small sample size with 7 consecutive patients, 3 with bilateral adrenal metastases.
Seidenwurm et al.[29]	1984	Retrospective observational study	• Moderate sample size • Clear documentation of bilateral disease via CT or autopsy • Representative of patients with bilateral metastases	• Used symptoms, signs or biochemistry suggestive of AI, as well as response to glucocorticoids as part of diagnostic criteria rather than ACTH-stimulation testing (only 2 patients had documented inappropriate response to ACTH testing out of those included as AI) • May have included patients with nephrectomy/adrenalectomy
Redman et al.[30]	1987	Prospective observational study with intervention arm	• Excluded treatment induced AI • Used ACTH stimulation test for diagnosis with clear documentation of values • Clear documentation of bilateral disease • Representative of patients with bilateral metastases	• Small sample size
Lutz et al.[31]	2000	Cross sectional observation study.	• Clear documentation of bilateral adrenal disease • Exclude patients with prior treatment that could affect adrenal function. • Used ACTH stimulation testing • Representative of patients with bilateral disease	• Small sample size • Diagnostic criteria for subclinical AI not validated (use of ACTH:cortisol ratio)
Lam et al.[32]	2002	Retrospective observational study	• Large sample size • Clear documentation of bilateral disease via autopsy, adrenalectomy or FNA • Population representative of patients with bilateral metastases	• Inconsistent use of ACTH stimulation test for diagnosis • Authors did not disclose the values for diagnosis of AI • Diagnosed AI by using signs, symptoms and biochemical evidence with unclear documentation of what this entails.
Delivanis et al.[13]	2016	Retrospective observational study	• Moderate sample size with bilateral disease • Confirmed radiological evidence of bilateral disease • Representative of population of interest	• No ACTH stimulation testing, used low cortisol and high ACTH levels to diagnosis AI

AI = adrenal insufficiency, ACTH = adrenocorticotropin hormone, CT = computer tomography, FNA = fine needle aspiration.