Comparison of Epidemiological Methods for Estimation of Hepatitis B Incidence and Residual Risk for Blood Donors in Southern Brazil

Table 5

HBsAg yield rate method for first-time and repeat blood donors in southern Brazil, 2004–2006.

Parameter	First-time; (𝑛=58679)	Repeat; (𝑛=35432)
HBsAg− & anti-HBc−^1	57435	35404
HBsAg− & anti-HBc+^1	1122	10
HBsAg+ & anti-HBc−^1	86	1
HBsAg+ & anti-HBc+^1	6	0
Yield rate (per 100000)	146.56	2.82
Incidence^2 per 100000 (95% CI)^3	1191.71; (848.80, 1741.28)	22.93; (0.58, 78.30)
Residual risk (95% CI)^4	1 : 520; (1 : 730, 1 : 356)	1 : 27003; (1 : 7908, 1 : 1067578)

¹Number of blood donors for each HBV markers combination (“−” and “+” after the markers stand for negative and positive test results, resp.).
²For the repeat donors, the incidence was calculated by dividing the yield rate by the 45 days (0.123 years) of time between the anti-HBc negative test result on screening and subsequent anti-HBC positive for the one HBsAg yield case. For the first time donors, the incidence was estimated by multiplying the repeat donors incidence with the ratio of the first-time to the repeat donors yield rate.
³Confidence interval.
⁴Using 59 days for the infectious window period.