The continuation of ART is mostly related to survival (but also willingness to continue). Survival might reflect the services offered but also depends on the baseline characteristics of the patients started on ART. Clinical, immunological and virological staging are independent predictors of survival under ART. Baseline characteristics of the cohort of patients should help in interpreting the results and, in particular, comparing ART sites.

Additional considerations:
If data on 24-month or 60-month retention are not available for patients that initiated antiretroviral therapy in 2010 or 2007, respectively, but available for patients that initiated antiretroviral therapy during an earlier time period (e.g. 2009 or 2008, or 2006 or 2005), please specify the period in the comment field: e.g. "Started antiretroviral therapy between [month]/[year] and [month]/[year]”.
The numerator does not require patients to have been on antiretroviral therapy continuously for the 24 month or 60 month period. For example, patients who may have missed one or two appointments or drug pick-ups, and temporarily stopped treatment since initiating treatment but are recorded as still being on treatment at month 24 or 60 are included in the numerator. On the contrary, those patients who have died, stopped treatment or been lost to follow-up at 24 or 60 months since starting treatment are not included in the numerator.
In countries where this indicator is not produced in all ART sites but in a sub-set of facilities, data should be interpreted keeping in mind the representativeness, and this should be stated in the Comments box.

Data utilization: Note any particularly low retention and assess reasons behind it, by analysing the distribution of those who are not on ART: dead, stopped, loss to follow up. If data is available, try to assess the lost-to-follow-up population to see if they are likely to be dead, stopped, or transferred out. Compare cohorts.