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Table 3 Transition probabilities (per three-month period) and data sources

From: The cost-effectiveness of Antiretroviral Treatment in Khayelitsha, South Africa – a primary data analysis

Input parameters

Data sources

Transition probability (range)

CD4 category at baseline for ART and No-ART

CD4 < 50 cells/ml

 

0.372 (0.349–0.395)

CD4 50–199 cells/ml

 

0.628 (0.605–0.651)

Probabilities of transitioning between alive Markov states

First-line regimen to second-line regimen

0–6 months

N/A – no patients switched

 

6–12 months

0.48% switched by 12 months

0.002 (0.001–0.006)

12–24 months

4.66% switched by 24 months

0.011 (0.007–0.015)

24–36 months

11.73% switched by 36 months

0.019 (0.014–0.026)

36–48 months

15.9% switched by 48 months

0.012 (0.005–0.024)

>48 months

Average over 0–48 months

0.011 (0.007–0.017)

No-ART, CD4 50–199 cells/ml to CD4 < 50 cells/ml

all quarters

Calculated to ensure 50% surviving at 24 months

0.040 (0.026–0.043)

Probabilities of transitioning to dead Markov states

ART CD4 < 50 cells/ml

0–3 months

86.9% surviving at 3 months

0.131 (0.107–0.159)

3–6 months

83.9% surviving at 6 months

0.034 (0.031–0.038)

ART CD4 50–199 cells/ml

0–3 months

95.9% surviving at 3 months

0.041 (0.030–0.054)

3–6 months

93.9% suriviving at 6 months

0.021 (0.019–0.024)

All patients on ART, irrespective of regimen

6–12 months

86.9% suriviving at 12 months

0.018 (0.017–0.020)

12–24 months

83.4% suriviving at 24 months

0.010 (0.008–0.012)

24–36 months

79.5% surviving at 36 months

0.012 (0.009–0.016)

36–48 months

76.2% suriviving at 48 months

0.010 (0.005–0.017)

>48 months

Average over 0–48 months

0.017 (0.013–0.021)

No ART CD4 count < 50 cells/ml

all quarters

20% surviving at 24 months1

0.182 (0.147–0.227)

No ART CD4 50–199 cells/ml

all quarters

50% surviving at 24 months with CD4 < 200 cells/ml2 divided by hazard ratio3

0.039 (0.034–0.043)

  1. 1 No-ART survival with CD4 < 50 cells/μl from Post, Wood et al [52]
  2. 2 No-ART survival with CD4 < 200 cells/μl from Badri, Bekker et al [27]
  3. 3 Hazard ratio for death in CD4 < 50 versus 50–199 cells/μl from Coetzee, Hildebrand et al [26]