We assess both risk and needs for pretrial release candidates. We do not, however, use the needs assessment as a predictor of successful completion of PTR, although we are reviewing that issue now and may change our policy.
We do use it for the supervising officers' use in later contacts with the defendants, since the officer should be aware of significant problems that could interfere with successful completion, and may require the officer to attempt to intercede with service providers or justice system officials to reduce or eliminate conflicts that could arise. Medical appointments (either due to physiological or psychological issues), social worker appointments, child care, etc., all have to be managed by someone to avoid conflicts with justice system appointments, and often the defendants we deal with have proven not to be particularly good managers of those issues.
It seems to me that the pragmatic view of the issue would nudge us toward using the needs assessment in scoring a case, since we don't use the PTR Risk/Needs just for prediction of success, but also as a measure of workload. If the defendants are not particularly risky as measured by the usual risk scoring instruments, but have a great many unmet needs, we have frequently found our officers spend as much, or more time with the very needy as they do with the very risky.