This site uses cookies to store information on your computer. I'm fine with this Cookie information

16. Viral load log10 number conversion

In its simplest form, a logarithm is how many of one number do we multiply to get another number?

For Log10, it is how many times you need to use 10 in a multiplication, to get the desired number.

For example: log10 of 1000 is the number of times 10 is multiplied to get to 1000 (10 x 10 x 10 = 1000) = 3

so 10 x 1 = 10 = 1 log10
     10 x 10 = 100 = 2 log 10
     10 x 10 x 10 = 1,000 = 3 log10
     10 x 10 x 10 x 10 = 10,000 = 4 log10
     10 x 10 x 10 x 10 x 10 = 100,000 = 5 log10
     10 x 10 x 10 x 10 x 10 x 10 = 1,000,000 = 6 log10
     10 x 10 x 10 x 10 x 10 x 10 x 10 = 10,000,000 = 7 log10
     10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 = 100,000,000 = 8 log10
     10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 = 1,000,000,000 = 9 log10

Why do we use log10?

It is very important to understand that repeat tests of the same blood sample give results that vary. This means that a meaningful change in viral load would be at least 0.5 log10 of the previous test result. For example, a change from 200,000 (5.3 log10) to 600,000 (5.78 log10) is within the normal variability of the test. A drop from 50,000 (4.7 log10) to 10,000 (4.0 log10) would however, be significant. The most important change is to reach an undetectable viral load.

Please note the numbers for the log10 below are not precise, but have been rounded up or down for ease of use.

Log10    IU/mL
              or
              copies/ml
 
0.1   1
0.2   2
0.3   2
0.4   3
0.5   3
0.6   4
0.7   5
0.8   6
0.9   8
1.0   10
1.1   13
1.2   16
1.3   20
1.4   25
1.5   32
1.6   40
1.7   50
1.8   63
1.9   79
2.0   100
2.1   126
2.2   158
2.3   200
2.4   251
2.5   316
2.6   398
2.7   501
2.8   632
2.9   794
3.0   1,000
3.1   1,259
3.2   1,585
3.3   1,995
3.4   2,512
3.5   3,162
3.6   3,981
3.7   5,012
3.8   6,310
3.9   7,943
4.0   10,000
4.1   12,589
4.2   15,849
4.3   19,953
4.4   25,119
4.5   31,623
4.6   39,811
4.7   50,119
4.8   63,096
4.9   79,433
5.0   100,000
5.1   125,893
5.2   158,489
5.3   199,526
5.4   251,189
5.5   316,228
5.6   398,107
5.7   501,187
5.8   630,957
5.9   794,328
6.0   1,000,000
6.1   1,275,000
6.2   1,600,000
6.3   2,000,000
6.4   2,500,000
6.5   3,250,000
6.6   4,000,000
6.7   5,000,000
6.8   6,500,000
6.9   8,000,000
7.0   10,000,000
7.1   12,500,000
7.2   16,000,000
7.3   20,000,000
7.4   25,000,000
7.5   32,000,000
7.6   40,000,000
7.7   50,000,000
7.8   63,000,000
7.9   79,000,000
8.0   100,000,000
8.1   126,000,000
8.2   159,000,000
8.3   200,000,000
8.4   251,000,000
8.5   316,000,000
8.6   400,000,000
8.7   500,000,000
8.8   631,000,000
8.9   800,000,000
9.0   1,000,000,000