Table 1. Assumptions around HCV infection date for HCV co-infected individuals in the UKR Register of HIV seroconverters.

HIV seroconversion Date*	First HCV positive Test	Assumed date of HCV infection
Before 01 January 2003	Before HIV seroconversion	HIV seroconversion date
	Later than or on the day of HIV Seroconversion and before 01 January 2003	Midpoint of last negative and first positive HCV test dates. If no negative test, then date of first positive test.
	Later than or on the day of HIV Seroconversion and after 01 January 2003	Midpoint of last negative and first positive HCV test dates, unless tests >1 year apart – in which case the midpoint of last assumed negative test date (annually from 01 January 2003 onwards) and first positive test.
Later than or on 01 January 2003	Before HIV seroconversion	Midpoint of last negative and first positive HCV test dates. If no negative test, then date of first positive test.
	Later than or at the same time as HIV Seroconversion	Midpoint of last negative and first positive HCV test dates, unless tests are >1 year apart – in which case the midpoint of last assumed negative test (annually 1 year after seroconversion date onwards) and first positive test.

*We assumed that routine testing for HIV positive individuals was taking place from 2003 according to BHIVA guideline