Determination of 50% endpoint titer using a simple formula

Table 3 Calculation of virus titre in mice using the new method

Log10 virus dilution	Mice		Death score
	Died	Inoculated
-1	10	10	10/10 = 1
-2	10	10	10/10 = 1
-3	10	10	10/10 = 1
-4	10	10	10/10 = 1
-5	10	10	10/10 = 1
-6	6	10	6/10 = 0.6
-7	1	10	1/10 = 0.1
Total	57		5.7

By using formula 1: log₁₀ 50% end point dilution = - (57/10 + 0.5) × 1 = -6.2; 50% end point dilution = 10^-6.2; the titre of the virus = 10^6.2 LD₅₀/mL. By using formula 2: log₁₀ 50% end point dilution = - (5.7 + 0.5) × 1 = -6.2; 50% end point dilution = 10^-6.2.