Measuring retention in HIV care: the elusive gold standard.

... visits: count and dichotomous missed visits, visit adherence, 6-month gap, 4-month visit constancy, and the HRSA HIV/AIDS Bureau (HRSA HAB) retention measure. Spearman correlation coefficients and separate unadjusted logistic regression models ...

http://www.citeulike.org/user/ajw/article/12738171