Table 3.

Primary outcome—AVF failure rates

Outcome	Clinical Group	Ultrasound Group	RR [95% CI]a	P	ARRb	NNT [95% CI]c
Immediate failure
all AVF: n failures	12	4			8.1%	12 [6, 132]
ITT: n = 218d	11.3%	3.6%	0.315 [0.105, 0.944]	0.028
surgery: n = 208e	11.9%	3.7%	0.315 [0.105, 0.944]	0.028
forearm AVF: n failures	11	4			11.1%	9
ITT: n = 131	16.7%	6.2%	0.369 [0.124, 1.100]	0.054
surgery: n = 126	17.5%	6.3%	0.364 [0.122, 1.081]	0.054
Primary failure
all AVF: n failures	33	24			11.0%	9
ITT: n = 218	31.1%	21.4%	0.688 [0.437, 1.084]	0.103
dialysis use: n = 186f	36.3%	25.3%	0.697 [0.449, 1.082]	0.104
forearm AVF: n failures	27	19			12.4%	8
ITT: n = 131	40.9%	29.2%	0.715 [0.444, 1.151]	0.139
dialysis use: n = 116	45.8%	33.3%	0.728 [0.460, 1.154]	0.171
Nonmaturationg
all AVF: n failures	21	20			4.6%	22
ITT: n = 218	19.8%	17.9%	0.901 [0.519, 1.565]	0.712
dialysis use: n = 170	26.6%	22.0%	0.827 [0.485, 1.409]	0.484
forearm AVF: n failures	16	15			5.0%	20
ITT: n = 126	25.4%	23.8%	0.938 [0.509, 1.729]	0.836
dialysis use: n = 101	33.3%	28.3%	0.849 [0.472, 1.526]	0.584

AVF failures are shown for all patients, for the clinical and for the ultrasound group, respectively; n failures means absolute number of AVF failures; % failures means percentage of AVF failures to total number AVF.

^aRelative risk of AVF failure with 95% CI [lower, upper limits].

^bAbsolute risk reduction of AVF failure.

^cNNT [95% CI]: Number needed to treat (i.e., the number of ultrasound scans needed to avoid one AVF failure; the 95% CI is shown for immediate failure but not for primary failure or the forearm subgroups because these are not statistically significant.

^dITT: analysis by intention to treat; i.e., for all patients randomized.

^eAnalysis restricted to patients who had surgery.

^fAnalysis restricted to AVF for which the outcome (dialysis use or failure) was known.

^gNonmaturation: primary failure excluding immediate failure.