Table 2 Respondent-driven sampling diagnostics by pooled surveys

From: Decline in HIV prevalence among female sex workers in Zimbabwe between 2013 and 2023

RDS diagnostics

Pooled surveys 2016–2017 (N = 4005)

Pooled surveys 2021–2023 (N = 4475)

Difference in means (95% CIs)

p-value

N

Cluster mean [range]

N

Cluster mean [range]

Homophily for HIV prevalence (survey round)a

4005

1.04 [0.91–1.22]

4475

1.07 [0.92–1.16]

N/A

N/A

Difference between ratio of egonet & sample proportion <25b

 

3.17 [0.0–6.3]

 

3.43 [1.6–5.3]

0.26 (−1.4–0.8)

0.630

Difference between ratio of egonet & sample proportion >35b

 

1.00 [0.0–1.3]

 

1.00 [0.7–1.4]

0.00 (−0.2–0.3)

0.820

 

n/N

%

n/N

%

  

% recruiters successfully recruiting 2 othersc

2100/2646

79.0 [71.3–88.9]

2276/2796

79.9 [66.7–89.3]

0.9 (−1.2–3.0)

0.410

% seeds with chains reaching the final waved

106/118

90.7 [50.0–100.0]

81/114

69.2 [33.3–100.0]

−21.5 (−31.5–−11.5)

<0.001

HIV prevalence by wavee (%)

      

Wave 0 (seeds)

52/91

54.1 [2.2–100.0]

43/80

54.6 [0−100.0]

0.5 (−24.0–25.0)

0.970

Wave 1

107/179

62.1 [39.5–95.4]

79/176

47.8 [10.4–77.2]

−14.3 (−27.7–−0.9)

0.038

Wave 2

211/357

59.1 [36.3–82.4]

130/346

41.4 [6.8–79.6]

−17.7 (−30.8–−4.7)

0.010

Wave 3

315/582

52.6 [35.0–78.9]

215/554

40.5 [23.2–66.4]

−12.2(−22.4–−1.9)

0.020

Wave 4

483/879

55.1 [28.3–76.3]

329/786

42.6 [27.4 – 69.1]

−12.5(−22.5–−2.8)

0.014

Wave 5

499/979

53.2 [20.6–74.0]

338/961

33.4 [17.0 – 48.4]

−19.8(−28.5–−11.1)

<0.001

Wave 6

277/562

44.3 [41.7–46.9]

356/1065

36.1 [3.4 – 100.0]

−8.2(−22.5–6.0)

0.240

Wave 7

182/376

49.0e

144/507

37.7 [0–96.3]

–

–

  1. Source data are provided as a Source Data file. Data are number of participants. P-values (two-sided) are based on t test.
  2. RDS respondent-driven sampling.
  3. aCalculated using all FSW included in the samples i.e. without restricting to those aged 18–39 years.
  4. bEgonet data was not collected in the 2017 survey.
  5. cCalculated using all recruiters that were included in the samples i.e. without restricting to those aged 18–39 years.
  6. dN is total seeds in the sample i.e. without restricting to those aged 18–39 years.
  7. eOnly 1 cluster in wave 7 in 2017 – could not calculate range.
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