FAQ: Protocols

  1. I'm an investigator for a multi-center study; do I need to write a CHOP-specific protocol?

    The IRB doesn't want and will not accept a CHOP-specific protocol for multi-center studies (unless you are the PI and this will be the protocol used at all sites). The IRB will accept one and only one protocol to serve as the official protocol for multi-center research. The IRB is obligated to ensure that the research uses sound scientific design. When there is more than one protocol the IRB cannot be certain if all centers will include all of the required procedures or carry them out the same way. If there is a need to describe study activities at CHOP than aren't well-described in either the protocol or the in the eIRB application, a protocol addendum may be created. Provided that the protocol is well-written, this should rarely be necessary.

  2. What is the difference between the number of subjects enrolled and the number evaluable?

    The Enrolled total is the number of subjects who consent to participate in the study. For a retrospective study, it would be the number of charts reviewed or specimens received. The Evaluable number is the total of the subjects that reach the required endpoint for the study.

    Example: 100 subjects might enroll, 10 fail screening, and 20 drop out before the final study visit that is required for assessing the primary efficacy endpoint. The enrolled number is 100, the evaluable number is 80 and 90 subjects will be included in the safety analysis.

    Example: 24 subjects are enrolled in a PK study but only 18 provide enough blood samples for their data to used in estimating PK parameters. The evaluable number is 18 and the enrolled is 24. All 24 subjects will be part of the safety analysis.

  3. I've enrolled 25 subjects but only 5 have completed the study; how many do I list on the continuing review form as evaluable?

    During a study with multiple visits, the investigator will not know how many of the enrolled subjects will ultimately be evaluable. The evaluable total at the time of continuing review should be based on those who have completed the study or reached the study visit where the primary endpoint assessment is made.

  4. I know how many evaluable subjects are needed from the power analysis; how do I estimate the enrolled number?

    The investigator should estimate the number of subjects who will fail screening, drop-out or be unable to complete required study procedures. This number when added to the required evaluable number will give an estimate of the number who will need to be enrolled. If fewer subjects drop-out then anticipated, the study might wind up with more evaluable subjects then anticipated. However, under-estimation of the number of subjects who will need to enroll in order to achieve the required evaluable total is often the bigger problem. Under-estimation can result in protocol deviations and burdens the investigator and IRB with protocol amendments to increase the approved enrollment number.

  5. How many subjects should I estimate for the CHOP target for multicenter studies?

    The total evaluable number for all sites is determined by the study protocol. The IRB prefers that the investigator use the highest total that could conceivably be enrolled at CHOP. This avoids the need for protocol amendments just to increase the permissible enrolled number.

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