Genital chlamydia prevalence in Europe and non-European high income countries: systematic review and meta-analysis

Abstract

Background: Accurate information about the prevalence of Chlamydia trachomatis is needed to assess national prevention and control measures.

Methods: We systematically reviewed population-based cross-sectional studies that estimated chlamydia prevalence in European Union/European Economic Area (EU/EEA) Member States and non-European high income countries from January 1990 to August 2012. We examined results in forest plots, explored heterogeneity using the I² statistic, and conducted random effects meta-analysis if appropriate. Meta-regression was used to examine the relationship between study characteristics and chlamydia prevalence estimates.

Results: We included 25 population-based studies from 11 EU/EEA countries and 14 studies from five other high income countries. Four EU/EEA Member States reported on nationally representative surveys of sexually experienced adults aged 18-26 years (response rates 52-71%). In women, chlamydia point prevalence estimates ranged from 3.0-5.3%; the pooled average of these estimates was 3.6% (95% CI 2.4, 4.8, I² 0%). In men, estimates ranged from 2.4-7.3% (pooled average 3.5%; 95% CI 1.9, 5.2, I² 27%). Estimates in EU/EEA Member States were statistically consistent with those in other high income countries (I² 0% for women, 6% for men). There was statistical evidence of an association between survey response rate and estimated chlamydia prevalence; estimates were higher in surveys with lower response rates, (p = 0.003 in women, 0.018 in men).

Conclusions: Population-based surveys that estimate chlamydia prevalence are at risk of participation bias owing to low response rates. Estimates obtained in nationally representative samples of the general population of EU/EEA Member States are similar to estimates from other high income countries.

Figure 1. Flow diagram of study identification, inclusion and exclusion.

Figure 2. Forest plot, overall estimate of chlamydia prevalence in women and men of all ages in EU/EEA and other high-income OECD countries in all included studies. CI, confidence interval.

The small filled diamond shows the point estimate, the lines either side are the 95% CI. Each row is a study or group within a study, with separate estimates from women and men, where available. In Denmark 2002, Group 1 received home sampling kits, Group 2 had to request a sampling kit by post. In USA 2012, separate estimates are reported for five survey cycles of the National Health and Nutrition Surveys. In Netherlands 2010, separate estimates were reported separately for Amsterdam and Rotterdam.

Figure 3. Forest plot, estimates of chlamydia prevalence in women ≤ 26 years in EU/EEA and other high-income OECD countries.

CI, confidence interval. The small filled diamond shows the point estimate, the lines either side are the 95% CI. Each row is a study or group within a study. In Denmark 2002, Group 1 received home sampling kits, Group 2 had to request a sampling kit by post. Estimates are shown separately for sexually experienced participants only or for the overall sample, in either national or sub-national populations.

Figure 4. Forest plot, estimates of chlamydia prevalence in men ≤ 26 years in EU/EEA and other high-income OECD countries. CI, confidence interval.

The small filled diamond shows the point estimate, the lines either side are the 95% CI. Each row is a study or group within a study. In Denmark 2002, Group 1 received home sampling kits, Group 2 had to request a sampling kit by post. Estimates are shown separately for sexually experienced participants only or for the overall sample, in either national or sub-national populations.

Figure 5. Meta-regression analysis of chlamydia prevalence estimates in women and men aged ≤25 years against calculated sex-specific response rate for all women and men in the study, in EU/EEA and other high-income OECD countries.

The size of the open circle corresponds to the precision of the prevalence estimate. n = number of studies. For women, n = 27, P = 0.003, I² 82.4%; men, n = 18, P = 0.018, I² 87.6%.

Figure 6. Meta-regression analysis of chlamydia prevalence estimates in participants of all ages against response rate, by national or sub-national study design.

Panel A, women; Panel B, men. The size of the open circle corresponds to the precision of the prevalence estimate. n = number of studies. For women, national studies, n = 10, P = 0.644, I² 46.8%; sub-national studies, n = 18 studies, P = 0.063, I² 91.23%; for men, national studies, n = 10, P = 0.729, I² 57.56%; sub-national studies, n = 15 studies, P = 0.267, I² 81.25%.