Table 3. Estimated proportion of persons who injected drugs (PWID) in the past year, by survey and combined by meta-analysis, United States.

Population	Survey	% PWID	95% Confidence Interval
Males
	NHANES	0.42	0.26	0.66
	NSDUH	0.30	0.26	0.35
	NSFG	0.45	0.29	0.60
	Combined estimate	0.36	0.26	0.47
Females
	NHANES	0.26	0.15	0.46
	NSDUH	0.14	0.12	0.16
	NSFG	0.28	0.16	0.40
	Combined estimate	0.21	0.10	0.32
Total
	NHANES	0.34	0.24	0.48
	NSDUH	0.22	0.19	0.25
	NSFG	0.36	0.27	0.46
	Combined estimate *	0.30	0.19	0.41

*Q₂ = 11.7, p<0.01, I² = 82.9.

NSDUH  =  National Survey of Drug Use and Health (2002–2009); NHANES = National Health and Nutrition Examination Survey (1999–2008); NSFG = National Survey of Family Growth (2002 and 2006–2008).