Incidence of pelvic inflammatory disease among women treated for gonorrhea or chlamydia.

Background: No estimate exists of the incidence of pelvic inflammatory disease (PID) after the occurrence of a recent bout of sexually transmitted disease (STD).
Methods: We used a computerized data file of prescriptions and medical encounters from the Fallon Community Health Plan to estimate the incidence rate of pelvic inflammatory disease (PID) among women with a recently treated episode of gonorrhea or chlamydia (STD). First we identified women with presumed gonorrhea or chlamydia on the basis of a combination of diagnostic codes for cervicitis, vulvovaginitis or Bartholin's abscess, and a computer record of a prescription for doxycycline. We then followed these women to estimate the incidence rate of PID after their treatment for gonorrhea or chlamydia. We estimated the number of cases of pelvic inflammatory disease in this cohort by selecting all women with an International Classification of Diseases (ICD) code of 614.9 entered for either an outpatient or inpatient diagnosis.
Results: We estimated the overall risk of PID to be about 9% during the 1-year period following treatment for gonorrhea or chlamydia, with a steep rise in risk coming within the first 45 days.
Conclusion: The risk of PID in the year after an episode of treated STD is high, but the highest period of risk is in the first few weeks. The shape of the risk curve indicates that some PID cases may result from treatment-resistant infections, or possibly from untreated reinfections.