Table 1.
Operating characteristics for CD4 monitoring algorithms with different frequencies of measurement and confirmatory testing requirements
| Confirmatory measurement? | CD4 threshold cells/μl | Time between measurements (months) | Median ART start time (months) | Mean over 61 months per patient
|
% starting ART
|
||
|---|---|---|---|---|---|---|---|
| Pre-treatment CD4 measurements | Months on ART | ||||||
| late1 | very late2 | ||||||
| No | 200 | 12 | >60 | 5.4 | 8.1 | 62.7 | 18.3 |
| 6 | >60 | 9.2 | 11.1 | 38.0 | 2.6 | ||
| 4 | 60 | 13.0 | 12.7 | 24.1 | 0.7 | ||
| 3 | 57 | 16.5 | 14.0 | 16.1 | 0.1 | ||
| adaptive 6/43 | >60 | 11.0 | 12.3 | 28.5 | 1.3 | ||
| adaptive 6/34 | 57 | 12.6 | 13.9 | 15.9 | 0.1 | ||
|
| |||||||
| 350 | 12 | 48 | 4.5 | 19.0 | 57.6 | 11.5 | |
| 6 | 36 | 7.1 | 24.0 | 35.3 | 1.6 | ||
| 4 | 32 | 9.6 | 26.5 | 22.4 | 0.2 | ||
| 3 | 30 | 11.8 | 28.4 | 15.1 | 0.1 | ||
| adaptive 6/4 | 36 | 7.9 | 25.3 | 28.1 | 0.7 | ||
| adaptive 6/3 | 33 | 8.3 | 27.0 | 18.9 | 0.1 | ||
|
| |||||||
| 500 | 12 | 24 | 3.4 | 31.8 | 52.0 | 15.7 | |
| 6 | 18 | 4.9 | 37.3 | 34.4 | 3.6 | ||
| 4 | 16 | 6.2 | 40.0 | 24.0 | 1.2 | ||
| 3 | 12 | 7.4 | 41.8 | 17.8 | 0.8 | ||
|
| |||||||
| Yes | 200 | 12 | >61 | 6.2 | 4.7 | 88.6 | 41.5 |
| 6 | >61 | 10.7 | 6.6 | 77.3 | 14.9 | ||
| 4 | >61 | 15.1 | 7.4 | 68.1 | 6.2 | ||
| 3 | >61 | 19.4 | 8.2 | 60.4 | 2.4 | ||
|
| |||||||
| 350 | 12 | 61 | 5.9 | 12.5 | 87.0 | 29.3 | |
| 6 | 49 | 9.6 | 15.9 | 76.0 | 8.9 | ||
| 4 | 49 | 13.0 | 17.7 | 66.6 | 3.3 | ||
| 3 | 46 | 16.3 | 19.0 | 59.2 | 1.3 | ||
|
| |||||||
| 500 | 12 | 37 | 5.2 | 23.4 | 87.5 | 39.7 | |
| 6 | 31 | 7.8 | 28.0 | 78.3 | 18.8 | ||
| 4 | 29 | 10.1 | 30.3 | 70.1 | 10.2 | ||
| 3 | 25 | 12.2 | 31.9 | 63.3 | 7.5 | ||
The percentage starting ART late is calculated as the number who start ART at any time after their latent CD4 count is first below the threshold divided by the number who have a latent CD4 count below the threshold at any time during the 60 months simulated.
The very late thresholds for ART initiation thresholds of 500, 350 and 200 cells/μl are defined as 350, 200 and 100 cells/μl, respectively. The percentage starting ART very late is then calculated as the number who start ART at any time after their latent CD4 count is first below the very late threshold divided by the number who have a latent CD4 count below the very late threshold at any time during the 60 months simulated.
The adaptive 6/4 monitoring protocol calls for 6-monthly CD4 measurement until a patient crosses a threshold of 500 and a subsequent 4-monthly schedule thereafter until ART initiation.
Same as above but with a subsequent 3-monthly CD4 measurement schedule.