The Role of Biomarkers Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) and Vasoactive Intestinal Peptide (VIP) in Chronic and Episodic Migraines: A Meta-Analysis

Table 2

Result of risk of bias assessment of the included studies.

Study	Bias domains
	Selection of comparison groups	Bias due to confounding	Ascertainment of exposure	Measurement of outcomes	Missing data	Reporting of results	Overall risk of bias
Han et al. [31]	Low	Low	Low	Low	Low	Low	Low
Morollon “1” et al. [16]	Moderate (only women were assigned controls)	Low	Low	Moderate (no measurement for episodic migraine)	Low	Low	Moderate
Morollon “2” et al. [17]	Low	Moderate (all patients were females)	Low	Low	Low	Low	Moderate
Pereda et al. [3]	Low	Low	Low	Low	Low	Low	Low
Togha et al. [25]	Low	Moderate (patients were under treatment with onabotulinum toxin type A)	Low	Low	Low	Low	Moderate