Final answer:
The provided references do not give a specific duration for patient screening before a standard FTR or 24HR appointment; thus, a direct answer cannot be determined from the available information.
Step-by-step explanation:
There is not a specific duration provided for patient screening before an FTR or 24HR standard appointment in the information given. The indirect ELISA test for HIV mentioned involves a scheduling notice of at least 3 weeks post a patient's last hospital visit, but this does not specify the actual time allocated for screening.
In patient care scenarios like surgery, 60 minutes prior is mentioned for confirming prophylactic antibiotics, but this is not directly related to the patient screening time for appointments. Furthermore, the reference to the 90th percentile being 13.5 minutes relates to wait times in a comparison example involving airline travel, which is not applicable to healthcare appointment screenings.