Comparison 1. Success of primary implantation.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Seldinger (subclavian & IJ) versus venous cutdown (cephalic vein) ITT	7	1006	Odds Ratio (M‐H, Fixed, 95% CI)	0.40 [0.25, 0.65]
2 Seldinger (subclavian vein) versus venous cutdown (cephalic vein) ITT	5	672	Odds Ratio (M‐H, Fixed, 95% CI)	0.23 [0.13, 0.41]
3 Seldinger (IJ vein) versus venous cutdown (cephalic vein) ITT	2	367	Odds Ratio (M‐H, Fixed, 95% CI)	0.62 [0.30, 1.28]
4 Seldinger (subclavian & IJ) versus venous cutdown (cephalic vein). On‐treatment analysis	7	972	Odds Ratio (M‐H, Fixed, 95% CI)	0.59 [0.36, 0.98]
5 Seldinger (subclavian vein) versus venous cutdown (cephalic vein). On‐treatment analysis	5	640	Odds Ratio (M‐H, Fixed, 95% CI)	0.27 [0.15, 0.49]
6 Seldinger (IJ vein) versus venous cutdown (cephalic vein). On‐treatment analysis	2	332	Odds Ratio (M‐H, Fixed, 95% CI)	0.48 [0.22, 1.03]