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Table 1 Determinants of providing a cell phone number by responders, per screening round

From: Keeping participants on board: increasing uptake by automated respondent reminders in an Internet-based Chlamydia Screening in the Netherlands

Package requests (N) Multivariate logistic regression
  Round 1 (N = 52628) Round 2 (N = 41729)
  n (%) OR (95%CI) p-value n (%) OR (95%CI) p-value
Cell phone number providers (n) 37,375    30,510   
Gender 37,375    30,510   
   Male 33.2 1.0   32.3 NA NA
   Female 68.8 1.2 (1.0-1.4) 0.008 67.7   
Age 37,374    30,510   
   16-19 14.7 1.0   15.1 1.0  
   20-24 39.2 1.0 (1.0-1.1) 0.23 40.4 1.1 (1.0-1.2) 0.08
   25-29 46.1 0.8 (0.8-0.9) < 0.001 44.5 0.8 (0.8-0.9) < 0.001
Ethnicity 37,374    30,510   
   Dutch 61.2 1.0   60.1 1.0  
   Surinam/Antillean 11.8 1.3 (1.2-1.4) < 0.001 11.5 1.3 (1.2-1.4) < 0.001
   Turkish/Moroccan 6.4 1.1 (1.0-1.2) 0.04 6.3 1.1 (1.0-1.2) 0.09
   Sub Sahara African 3.4 1.5 (1.3-1.8) < 0.001 4.1 1.7 (1.5-2.0) < 0.001
   Western, other 8.0 1.0 (0.9-1.1) 0.66 8.6 1.0 (0.9-1.1) 0.87
   Non-Western, other 9.2 1.1 (1.1-1.2) 0.002 9.4 1.2 (1.1-1.3) < 0.001
Region 37,375    30,510   
   Rotterdam 57.4 ns ns 55.0 1.0  
   Amsterdam 39.3    38.3 1.0 (0.9-1.0) 0.35
   South-Limburg 3.3    6.7 0.8 (0.7-0.9) < 0.001
Community risk level 37,375    30,510   
   Low 34.9 1.0   34.4 1.0  
   Medium 50.1 0.9 (0.8-0.9) < 0.001 49.0 0.9 (0.9-1.0) 0.006
   High 15.0 1.0 (0.9-1.0) 0.24 16.6 0.9 (0.9-1.1) 0.82
Educational level 23,229    17,172   
   Low 5.0 1.0   4.9 1.0  
   Medium 28.7 0.9 (0.8-1.0) 0.17 28.8 1.0 (0.8-1.2) 0.74
   High 66.3 0.8 (0.7-0.9) 0.007 66.3 0.8 (0.7-1.0) 0.05
Ethnicity SP 13,998    9,638   
   Concordant(NL/NL) 54.8 1.0   54.1 ns ns
   Discordant (NL/non-NL) 26.9 1.0 (0.9-1.1) 0.55 26.7   
   Concordant (non-NL/non-NL) 18.3 1.4 (1.2-1.5) < 0.001 19.2   
Age at first sexual contact 22,728    16,752   
   ≤5 29.3 1.0   30.6 1.0  
   16-18 52.6 0.8 (0.8-0.9) < 0.001 52.9 0.8 (0.8-0.9) < 0.001
   ≥ 19 18.1 0.7 (0.6-0.8) < 0.001 16.5 0.6 (0.6-0.7) < 0.001
Number of sexual partners < 6 months 22,459    16,612   
   No partner(s) 8.5 1.0   7.9 ns ns
   1 steady partner 49.4 1.2 (1.0-1.5) 0.12 44.5   
   1 casual partner 11.7 1.2 (1.0-1.5) 0.16 13.0   
   ≥ 2 partners (incl. steady partner) 30.4 1.5 (1.1-1.9) 0.003 34.6   
Duration steady partnership 22,812    16,841   
   < 1 year 15.9 1.0   17.7 1.0  
   1-2 years 20.9 1.0 (0.9-1.1) 0.62 19.5 1.0 (0.9-1.1) 0.18
   3-5 years 15.0 0.8 (0.7-0.9) < 0.001 12.7 0.9 (0.8-1.0) 0.01
   ≥ 6 years 9.1 0.8 (0.7-0.8) < 0.001 6.9 0.7 (0.6-0.8) < 0.001
   No steady partner 39.1 1.5 (0.9-2.4) 0.13 43.2 0.8 (0.7-0.9) 0.001
Condom use last contact CP 8,124    6,926   
   Yes 47.7 1.0   44.0 1.0  
   No 52.3 1.2 (1.1-1.3) < 0.001 56.0 1.1 (1.1-1.3) 0.02
Condom use last contact SP 13,876    9,547   
   Yes 15.8 1.0   16.0 NA NA
   No 84.2 1.2 (1.1-1.3) < 0.001 84.0   
History of STI 3,175    8,442   
   No STI ever 68.1 1.0   68.8 1.0  
   Yes, < 6 months 4.0 1.2 (0.8-2.0) 0.38 4.0 1.2 (0.9-1.5) 0.25
   Yes, ≥ 6 months 27.9 1.2 (1.0-1.5) 0.03 27.2 1.2 (1.1-1.3) 0.002
Symptoms of an STI 5,649    13,284   
   Yes 38.1 ns ns 40.1 1.0  
   No 61.9    59.9 0.7 (0.8-0.9) < 0.001
  1. OR, odds ratio; CI, confidence interval; NA, not applicable (p ≥ 0.2 in univariate analysis); ns, not significant (p > 0.05 in multivariate analysis); MSM, men having sex with men, STI, sexually transmitted infection(s); SP, steady partner; CP, casual partner. Ethnicity 'Western other' included Oceania, North America, Canada, Europe (excluding the Netherlands and Turkey); 'Non Western other' included Central and South America, Middle East, South and South-East Asia (excluding Surinam, Antilles, Aruba, Morocco and North Africa). Non-significant variables in the multivariate models in both screening rounds are not shown: SES-score, living situation, concurrent partners, sexual preference, history of STI testing