Table 3.

Estimated Screening Rates When Distribution of Patient’s by Group and Screening Rates for Patients in Specific Groups Differ Across Centers

	Population distribution by group			Expected performance (overall screening rate)
	Proportion of CHC patients in group 1	Proportion of CHC patients in group 2	Proportion of CHC patients in group 3	Sample design A (most inclusive)	Sample design B	Sample design C (least inclusive)
	Actual screening rates by patient group			(Sampled from groups 1, 2, 3)	(Sampled from groups 1, 3)	(Sampled from group 3)
Scenario 1. Screening rates are identical across groups	1 = 0.5	2 = 0.5	3 = 0.5
	0.33	0.33	0.33	0.50	0.50	0.50
	0.35	0.50	0.15	0.50	0.50	0.50
	0.30	0.35	0.35	0.50	0.50	0.50
	0.20	0.25	0.55	0.50	0.50	0.50
	0.10	0.15	0.75	0.50	0.50	0.50
Scenario 2: Screening rates vary minimally across groups	1 = 0.45	2 = 0.5	3 = 0.55
	0.33	0.33	0.33	0.50	0.525	0.55
	0.35	0.50	0.15	0.49	0.512	0.55
	0.30	0.35	0.35	0.503	0.525	0.55
	0.20	0.25	0.55	0.518	0.534	0.55
	0.10	0.15	0.75	0.533	0.542	0.55
Scenario 3: Screening rates vary moderately across groups	1 = 0.35	2 = 0.5	3 = 0.65
	0.33	0.33	0.33	0.50	0.575	0.65
	0.35	0.50	0.15	0.407	0.535	0.65
	0.30	0.35	0.35	0.508	0.575	0.65
	0.20	0.25	0.55	0.553	0.603	0.65
	0.10	0.15	0.75	0.598	0.625	0.65
Scenario 4: Screening rates vary greatly across groups	1 = 0.25	2 = 0.5	3 = 0.75
	0.33	0.33	0.33	0.50	0.625	0.75
	0.35	0.50	0.15	0.45	0.558	0.75
	0.30	0.35	0.35	0.513	0.625	0.75
	0.20	0.25	0.55	0.588	0.672	0.75
	0.10	0.15	0.75	0.663	0.708	0.75

Standard deviations are all approximately 0.05 so these are not presented individually

Estimates are derived for sample designs A, B, and C. Each sample design encompasses a random sample of patients from three mutually exclusive groups (sampled according to their distribution at the center) (see Fig. 1)

Group 1 patients were seen only in 2002 or 2003. Group 2 patients were seen only in 2004 (the assessment year). Group 3 patients were seen in 2004 AND at least once in either 2002 or 2003