Table 3.

Risk for bias in studies comparing the outcomes of percutaneous needle aspiration (PNA) and percutaneous catheter drainage (PCD) in the management of liver abscess

Studies	Sequence generation	Allocation concealment	Blinding of participants and personnel	Blinding of outcome assessment	Incomplete outcome data	Selective reporting
Rajak et al.17	Uncertain	High risk	Uncertain	Uncertain	High risk	High risk
Yu et al.18	Low risk	Low risk	Low risk	Low risk	Low risk	Low risk
Zerem & Hadzic19	Low risk	Low risk	Uncertain	Uncertain	High risk	High risk
Singh et al.20	Low risk	Low risk	Uncertain	Uncertain	Low risk	Low risk
Singh et al.21	Low risk	Low risk	Uncertain	Uncertain	Low risk	High risk

Risk for bias was classified as low, uncertain or high. The detail of each grade is referred to in the Cochrane Handbook for Systematic Reviews of Interventions.¹⁵