Epidemiology and Infection

  • Epidemiology and Infection / Volume 141 / Issue 09 / September 2013, pp 1953-1964
  • Copyright © Cambridge University Press 2012 The online version of this article is published within an Open Access environment subject to the conditions of the Creative Commons Attribution-NonCommercial-ShareAlike licence <http://creativecommons.org/licenses/by-nc-sa/2.5/>. The written permission of Cambridge University Press must be obtained for commercial re-use.
  • DOI: http://dx.doi.org/10.1017/S0950268812002567 (About DOI), Published online: 19 November 2012

Original Papers


Testing for Chlamydia trachomatis: time trends in positivity rates in the canton of Basel-Stadt, Switzerland


a1 Swiss Tropical and Public Health Institute, Basel, Switzerland

a2 University of Basel, Basel, Switzerland

a3 Viollier AG, Allschwil, Switzerland

a4 University Hospital Basel, Basel, Switzerland

a5 Swiss Federal Office of Public Health, Bern, Switzerland


National health statistics report a 2·5-fold increase in laboratory-confirmed Chlamydia trachomatis (CT) cases over the last decade in Switzerland where no CT screening programme exists. We obtained essential denominator information to describe the epidemiology of CT in the canton of Basel-Stadt, an urban canton in north-western Switzerland. Laboratories reporting at least two CT infections from Basel-Stadt residents to the SFOPH in 2010 provided demographic and test-related data. CT positivity rates were calculated for 2002–2010. The influences of test year, age, sex and laboratory on CT positivity were investigated in a multivariable model. Positivity differed between sexes and age groups. In our sample of 32 034 records, female and male CT positivity rates were 4·7% and 11·1%, respectively. Test year was significantly associated with test outcome in the multivariable analysis but no time trend was observed. CT positivity did not change over the past 9 years in Basel-Stadt. In contrast to other European countries without CT screening, we found no evidence that the observed increase of Chlamydia cases in the national notification system represents an epidemiological trend, but rather results from an increased testing frequency.

(Received June 13 2012)

(Revised September 19 2012)

(Accepted October 21 2012)

(Online publication November 19 2012)

Key words

  • Chlamydia trachomatis ;
  • positivity rate;
  • surveillance;
  • Switzerland;
  • time trend


c1 Author for correspondence: Dr D. Mäusezahl, Swiss Tropical and Public Health Institute, Socinstrasse 57, PO Box, CH–4002 Basel, Switzerland. (Email: daniel.maeusezahl@unibas.ch)