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Table 1 Compositional bias of the follow-up sample based on the behavioural risk factors associated with HIV in the baseline study

From: HIV incidence from the first population-based cohort study in India

  

Proportion having this risk factor

 

Relative impact on HIV estimationb

 

Variables

Baseline HIV prevalence

Among those who did not participate in follow-up

Among those who participated in follow-up

Relative impact of risk factor on HIV per unit populationa

Among those who did not participate in follow-up

Among those who participated in follow-up

Ratio of participated to not participatedc

Urban men (Number not participated, number participated)

       

Not circumcised (831, 2227)

3.95

0.806

0.725

1.00

3.184

2.864

 

More than one lifetime woman sex partners or ever visited sex worker (1127, 1815)

4.23

0.433

0.440

0.76

1.392

1.413

 

More than two lifetime women sex partners or ever visited sex worker (1131, 1817)

4.49

0.333

0.341

0.58

0.868

0.887

 

Have sex after consuming alcohol (1128, 1816)

5.41

0.234

0.230

0.58

0.734

0.721

 

Had tattooing (1145, 1841)

7.45

0.076

0.088

0.27

0.153

0.177

 

Used any recreational drugs (1131, 1798)

14.29

0.016

0.010

0.13

0.030

0.019

 

Men who had sex with men (830, 2226)

11.25

0.020

0.023

0.13

0.029

0.034

 

Had blood transfusion (1145, 1841)

8.08

0.029

0.029

0.10

0.023

0.023

 

Overall urban men

2.45

   

6.413

6.138

0.957

Rural men (Number not participated, number participated)

       

More than two lifetime women sex partners or ever visited sex worker (830, 2226)

2.83

0.380

0.412

0.44

0.473

0.514

 

More than one lifetime woman sex partner or ever visited sex worker (830, 2226)

2.28

0.525

0.574

0.40

0.479

0.523

 

Have sex after consuming alcohol (830; 2,225)

3.20

0.246

0.235

0.28

0.220

0.211

 

Not circumcised (1131, 1816)

1.97

0.915

0.909

0.13

0.234

0.233

 

Had tattooing (838, 2243)

2.99

0.053

0.067

0.05

0.008

0.010

 

Had blood transfusion (838, 2242)

3.51

0.013

0.020

0.02

0.001

0.001

 

Used any recreational drugs (831, 2227)

3.00

0.011

0.010

0.01

0.000

0.000

 

Men who had sex with men (1128, 1815)

2.00

0.012

0.018

0.00

0.000

0.000

 

Overall rural men

1.72

   

1.415

1.492

1.054

Urban women (Number not participated, number participated)

       

More than one lifetime man sex partners (1058, 1941)

8.33

0.050

0.052

0.21

0.087

0.091

 

Blood transfusion done (838, 2288)

2.08

0.074

0.099

0.01

0.002

0.002

 

Overall urban women

1.90

   

0.089

0.093

1.045

Rural women (Number not participated, number participated)

       

More than one lifetime man sex partners (826, 2270)

3.00

0.126

0.113

0.21

0.079

0.071

 

Blood transfusion done (1113, 2015)

3.20

0.054

0.073

0.01

0.002

0.002

 

Overall rural women

1.57

   

0.081

0.074

0.907

  1. aRelative impact of risk factors on HIV per unit population were published earlier from this study; these are based on computation of population impact number using the relative risk of HIV associated with that factor and the prevalence of that factor [26].
  2. bRelative impact on HIV estimation calculated by multiplying these three separately for those who participated and those who did not participate in the follow-up: HIV prevalence in those having that factor, proportion having this factor among those who participated/did not participate, and relative impact of that factor on HIV in a unit population.
  3. cRatio for each group (urban men, rural men, urban women, rural women) calculated by summing up the relative impact on HIV estimation for all factors in each group separately for those who participated and those who did not participate and divided the former number with the later. This ratio would give the over- or under-estimation of HIV in each group from those who participated in the follow-up based on the distribution of the risk factors in those who participated and those who did not.
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BMC Infectious Diseases

ISSN: 1471-2334

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