Fig. 4

Representative standard curve of anti-HBs qELISA_v.2 fitted by 4-parameter logistic regression. Anti-HBs reference standards consisted of 0, 10, 50, 150, 500, and 1000 IU/L. The duplicate readings for each standard were averaged and the average zero standard optical density was subtracted. In equation y = (A-D)/(1 + x/C)^∧B) + D, A = − 0.00767, B = 0.942, C = 710, and D = 4.17 and R^∧2 = 1