Selected variables for HIV care pattern determination*
| Measure | Type of output; calculation overview | Observation time needed to calculate |
| Missed visit | Dichotomous; were there any missed visits in the interval? Count; number of missed visits in the interval | At least 6 months |
| Appointment adherence | Continuous; attended appointments divided by (attended appointments plus missed appointments) | Patient: at least 1 year; clinic: as short as 1 day |
| Constancy, 3-month or 4-month intervals | Categorical; number of 3-month or 4-month intervals with at least one attended visit | At least 6–8 months |
| Constancy, 6-month intervals | Categorical; number of 6-month intervals with at least one attended visit | At least 1 year |
| Constancy, 6-month intervals, longer term | Dichotomous; At least one attended visit in each 6-month interval with at least 60 days between visits | At least 2 years |
| Constancy, HIV/AIDS Bureau | Dichotomous; At least two attended visits in 12 months, separated by at least 90 days | At least 1 year |
| Gaps | Dichotomous; did the time between two contiguous attended visits exceed a threshold (eg, 6 months)? | At least 1 year |
| Continuous; what is the longest duration of time between two contiguous attended visits? |
*Definitions for visits have been previously described elsewhere.25