[Testing pattern and prevalence of Chlamydia infection among women].
BACKGROUND
Chlamydia notification rates have increased in Norway over the recent years. The increase in notification cannot be interpreted as an increase in chlamydia prevalence since knowledge of testing patterns and prevalence of chlamydia by sex and age is virtually absent.


METHODS
A data set, applying the woman as unit for analyses, comprising all test activity in one Norwegian county, was created for the period 1990-2003 (women 15-59 years old, resident in Sør-Trøndelag County, n = 56,220). Tests registered within 60 days from the previous test were excluded. Outcome measures are age-specific testing rates (first test), cumulative incidence of first test and incidence of repeated testing, proportion of positive first tests and cumulative incidence of being diagnosed with chlamydia before the age of 25, and 12-month incidence of chlamydia.


RESULTS
Testing rates were high among young women throughout the study period. By the age of 25, almost all women had been tested at least once for chlamydia (85-90%). By the end of the year following the first test, one in five women with a negative first test and one in three women with a positive first test had been tested for chlamydia at least once more. The proportion of positive tests was highest among the youngest women (9-11% for women 15-24 years from 2000). Cumulative incidence of diagnosed chlamydia by the age of 25 years was 15% for women born 1976-79. Incidence of chlamydia during the first year after the first test was 2-3%. The relative risk for being diagnosed with chlamydia after the first test was highest for women who initially tested positive, and for teenagers.


CONCLUSIONS
The prevalence of chlamydia is high among young women. However, many women are not tested within a reasonable time after their first intercourse. Increased testing rates among teenagers can be achieved by focusing on easily available tests implying self-sampling methods.
Avdeling for epidemiologisk forskning, SINTEF Helse, 7465 Trondheim. inger.bakken@sintef.no
Inger Johanne
IJ
Bakken
Svein Arne
SA
Nordbø
Finn Egil
FE
Skjeldestad
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D002690:Chlamydia Infections / Q000175:diagnosis / Q000453:epidemiology*; D002692:Chlamydia trachomatis / Q000302:isolation & purification*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D009664:Norway / Q000453:epidemiology; D015995:Prevalence