Table 1

Incidence rate (IR) of symptomatic and asymptomatic chlamydia, gonorrhoea and syphilis among PrEP users, AMPrEP cohort study, August 2015–February 2020, Amsterdam, the Netherlands

Scheduled study visits only (n=366 persons, n=4974 visits)Including additional STI visits (n=366 persons, n=5750 visits)
SymptomaticAsymptomaticSymptomaticAsymptomatic
EventsPYIR (95% CI)*EventsPYIR (95% CI)*EventsPYIR (95% CI)*EventsPYIR (95% CI)*
Any chlamydia7213035.5 (4.4 to 7.0)355130327.3 (24.6 to 30.2)162130812.4 (10.6 to 14.4)386†130829.5 (26.7 to 32.6)
Any gonorrhoea10413038.0 (6.6 to 9.7)354130327.2 (24.5 to 30.2)240130818.3 (16.2 to 20.8)388†130829.7 (26.9 to 32.8)
Syphilis2613032.0 (1.4 to 2.9)7913036.1 (4.9 to 7.6)6213084.7 (3.7 to 6.1)84†13086.4 (5.2 to 8.0)
Any chlamydia or gonorrhoea‡146130311.2 (9.5 to 13.2)636130348.8 (45.2 to 52.8)337130825.8 (23.2 to 28.7)690†130852.7 (49.0 to 56.8)
Any chlamydia, gonorrhoea or syphilis‡162130312.4 (10.7 to 14.5)693130353.2 (49.4 to 57.3)379130829.0 (26.2 to 32.0)749†130857.3 (53.3 to 61.5)
  • *Per 100 PY.

  • †Additional asymptomatic STIs were found during the additional in-between STI visits. We defined an infection as asymptomatic if no symptoms were reported during triage and if the participant was not notified for possible exposure to an STI by a sexual partner. To assess symptoms, we used the data completed by the study physician or nurse during triage. It is possible that participants indicated they had symptoms or were notified to make an appointment, but then did not disclose any symptoms or notification during triage and were thus classified as asymptomatic.

  • ‡The diagnosis of multiple STIs at a (study or extra) visit was counted as one incident event.

  • AMPrEP, Amsterdam PrEP demonstration project; PrEP, pre-exposure prophylaxis; PY, person-years.