Viral load – converting log values to numbers
The range of viral load is so wide that results are often given as results from a logarithmic (log) scale.
This is an easier way to deal with very large and very small numbers at the same time. Less than 50 copies/mL for most people on treatment is 1.7 logs. In very early infection, a viral load of 10 million copies is 7.0 logs.
Log value is a measurement used to describe HIV and expresses the viral load values as a power of ten (written log10). The scale is used because large changes can only be captured on graphs or diagrams by using a log scale. This turns large numbers of copies/mL into ‘manageable’ figures.
Table: HIV RNA viral load log value–number conversion
| Log10 | 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 |
| Log10 | copies/mL |
|---|---|
| 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 |
| Log10 | copies/mL |
|---|---|
| 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 |
| Log10 | copies/mL |
|---|---|
| 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 |
| Log10 | copies/mL |
|---|---|
| 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 |
| Log10 | copies/mL |
|---|---|
| 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 |
Source: Learning resources in Treatment Training for Advocates.
Last updated: 29 March 2010.