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Table 1 Number of enrolled participants required to achieve the targeted effective number of person years of follow-up

From: Strengthening HIV surveillance in the antiretroviral therapy era: rationale and design of a longitudinal study to monitor HIV prevalence and incidence in the uMgungundlovu District, KwaZulu-Natal, South Africa

 

Time point

 

T1 and T2

T3 and T4

Cross sectional survey (Baseline) (age range 15–49 years)

 Number at baseline

10,000

10,000

 HIV Prevalence

20 %

20 %

 Number expected to be HIV negative

8000

8000

Longitudinal follow-up cohort (age range 15–35 years)

 Design effect

1.1

1.1

 Number of individuals in the HIV negative cohort

6400

6400

 Assumed HIV Incidence rate

3 %

3 % reduced by 30 %

 Loss to Follow-up adjustment

15 %

15 %

 Number expected to be retained in cohort

5440

5440

 Number of HIV endpoints assumed

163

114

 Total number of endpoints assumed across both cohorts

277

 Probability of Correct Inference

84 %

84 %

  1. T1 = Cross sectional Survey 1
  2. T2 = Embedded cohort 1
  3. T3 = Cross sectional Survey 2
  4. T4 = Embedded cohort 2