Table 3.

Mean and median scores of quality items across NIDU studies in our sample

	Mean	Median
NIDU screening items*
1. Was one of the stated aims to study the disease in NIDU's	0.57	1
2. Is there a method for minimizing misclassification bias	0.32	0
3. Was NIDU definition and method of drug use clear?	0.75	1
Subtotal: NIDU Screening Score**	1.64	1.5
Other items*
4. Aside from any inclusion criteria, were there any demographics/characteristics of the sample for the NIDU sample?	0.39	0
5. Did the authors control/stratify for any relevant (drug-user related) confounders/co-variates for the NIDU sample?	0.32	0
6. Did the authors assess any possible biologic mechanisms for disease transmission attributable to non-injection use?	0.29	0
7. Were inclusion criteria well-described?	0.93	1
8. Were exclusion criteria well-described?	0.61	1
9. Were data collected in a similar manner for all participants?	1.00	1
10. Was outcome (HCV) assessed using both antibody test and confirmatory test?	0.32	0
11. Was sample size sufficient (>=100 NIDU participants)	0.61	1
12. Were the number of subjects and percentages consistent?	1.00	1
Total quality scores***	7.11	7

^*Each item was scored 0 or 1 (absent, present) for each report

^**Items 1-3. Total summed scores ranged from 0 to 3.

^***Items 1-12. Total summed scores ranged from 3 to 12.