Reporting Unpaid Debt

Does anyone have recommendations as to reporting unpaid debt to credit bureaus? We currently do not use a collection agency, we have a dedicated guarantor collector who follows those accounts. We have processes in place, we have few accounts were patients are not responding to any collection attempts or statements. With those accounts we are coming to the point that we have exhausted all collection attempts. We are now wanting to take the next step and forward this debt to the credit bureau but I am unsure where to start. Any feed back is appreciated.

We use a collection agency

And our consent to treatment states "any unpaid balances will be transferred to a collection agency with a 23% additional fee." The 23% covers the charge the agency charges us on balances that they collect.
You could ask local docs for recommendations of agencies in your area and their success rate. There are a million out there including some that use strong arm techniques and your reputation is on the line (even with deadbeats) so pick carefully.