I think to be able to help you it would be good to understand your process better.
Who gives a MRN to the patient?
I assume that each MRN should be given only once and it should identify a patient, no matter which site he/she is at, correct?
My suspicion is that this is rather a internal organization problem, then a problem with the survey it self. But I think we don't know enough about what you are doing, what the process is and how the MRNs work in your organization.
I answer at the LimeSurvey forum in my spare time, I'm not a LimeSurvey GmbH employee.
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