Studies should, therefore, use a variety of databases, including not only emergency department records, but also general medical record reviews and insurance and Medicare/Medicaid claims to detect outpatient visits.
Emergency records are not thorough enough to detect the total outpatient visits. 
mnli hypothesis: Emergency records are not thorough enough to detect the total outpatient visits.  premise: Studies should, therefore, use a variety of databases, including not only emergency department records, but also general medical record reviews and insurance and Medicare/Medicaid claims to detect outpatient visits.