Table 4.

Eligibility criteria for review on biochemical markers.

Study characteristic	Inclusion criteria	Exclusion criteria
Participants/population	Patients with primary neuroendocrine tumors and patients who underwent surgery for primary liver tumors with a curative intent and were followed up for the detection of potential liver metastases	Studies that do not report the assessment of resectability (second scientific question)
	Patients over the age of 18 years old	Children or adolescents (under the age of 18 years)
		Studies that do not report the diagnostic accuracy (first scientific question)
Test of interest	Tests of biochemical markers detecting liver metastases, and for the post treatment follow-up of liver metastases: 1) Chromogranin A 2) Chromogranin B 3) Serotonin 4) Tumor specific hormones (Glucose, Insulin, Proinsulin, C-Peptide, Gastrin, Glucagon, Vasoactive Intestinal Peptide, Somatostatin, Neuron Specific Enolase)
Reference standard	The different biochemical markers Chromogranin A and B, Serotonin and tumor specific hormones will be compared
Control	The histopathological diagnosis of the resected specimen or a tumor biopsy will be considered as the reference standard
Study design	Randomized controlled trials (RCTs)
	Prospective and retrospective comparative cohort studies
	noncomparative cohort studies
	Case-control studies
	Case series
Primary outcome	Diagnostic accuracy of the different biochemical markers (sensitivity and specificity)
Secondary outcome	Additional diagnostic accuracy measures of the different biochemical markers (accuracy, positive and negative predictive values, positive and negative diagnostic likelihood ratios, etc)