Table 1:
Inputs, outputs, and formulas for assessing PrEP success
| Output score | Criterion threshold | Formula | |
|---|---|---|---|
| Success criterion 1: maintains HIV uninfected status (a) | |||
| What is the PrEP client’s HIV status at the clinic visit? (d) | Negative=n, positive=p, or unknown=u | HIV status negative (n) or unknown (u) at all clinic visits, meets success criterion 1 | If (d=n or d=u) then a=1; otherwise a=0 |
| Criterion 2: PrEP persistence (b) | |||
| Did the PrEP client return for their follow-up clinic visit? (e) | Yes=1, no=0; if PrEP client does not miss >1 clinic visit during the 12-month period they are considered engaged in care; if client is on PrEP and misses >1 clinic visit they are considered to have dropped out of care | If client returned for follow-up clinic visit (e) and is either on PrEP (f) or stopped PrEP in consultation with the health-care provider (g), meets success criterion 2 | If e=1 and (f=1 or g=1) then b=1; otherwise b=0 |
| Was PrEP dispensed to the PrEP client? (f) | Yes=1, no=0 | If client returned for follow-up clinic visit (e) and is either on PrEP (f) or stopped PrEP in consultation with the health-care provider (g), meets success criterion 2 | If e=1 and (f=1 or g=1) then b=1; otherwise b=0 |
| Was PrEP stopped in consultation with the health-care provider? (g) | Yes=1, no=0; if PrEP-client does not return for follow-up clinic visit this indicator will be scored 0; if client does not return during the follow-up period, but stopped PrEP in consultation with the provider, they are not lost to follow-up; if the PrEP-client does not attend 2 consecutive months of follow-up visits they are lost to follow-up and assumed to have stopped PrEP without consultation with the provider | If client returned for follow-up clinic visit (e) and is either on PrEP (f) or stopped PrEP in consultation with the health-care provider (g), meets success criterion 2 | If e=1 and (f=1 or g=1) then b=1; otherwise b=0 |
| Criterion 3: appropriate PrEP use* (c) | |||
| According to screening, is the PrEP-client at substantial risk of HIV infection? (h) | Yes=1, no=0; in countries where formal risk screening is not done, a prescription from a clinician is considered adequate to indicate a substantial risk of infection | If client is at substantial risk of HIV infection (h) and dispensed PrEP (f), meets success criterion 3 | If h=1 and f≠1 then c=0; otherwise c=1 |
If f=1 and g=1 (more than once) and h=1 (more than once) PrEP success score=1; otherwise=0. PrEP=pre-exposure prophylaxis.
*
Being appropriately on PrEP depends on a country’s guidelines for determination of risk.