QRDA category I files are generated one per patient, and should cover all of the data elements required to compute the quality measures whose computation is being certified. The HL7 QRDA Implementation Guide is essential reading, and describes the data elements that must/may be included. A QRDA-I file indeed contains data relating to multiple visits. Unfortunately, at this time, the only way to associate clinical data with an encounter is temporally -- the timing of the diagnosis/result/med-order/etc indicates whether it is associated with the visit. Here is additional feedback from Lantana: A QRDA file may have multiple visits of a single patient. In that case, the clinical data of patient will be linked to an encounter via timestamp. For instance, a QRDA may have two inpatient encounters (encounter_1, and encounter_2), a patient has lab tests in both encounter. encounter_1: from 2011-01-01 to 2011-01-10 encounter_2: from 2011-02-05 to 2011-02-11 lab_1 exam: occurred 2011-01-05 09:30 AM lab_2 exam: occurred 2011-02-07 12:30 PM As lab_1 exam's timestamp falls into the encounter_1's date range, thus the lab_1 exam is linked to encounter_1. Same as lab_2 exam, it is linked to the encounter_2 by comparing the date range.