Determinants of frequency and longevity of hospital encounters' data use.
BACKGROUND
The identification of clinically relevant information enables improvement in user interfaces and in data management. However, it is difficult to identify what information is important in daily clinical care, and what is used occasionally. This study aims to determine for how long clinical documents are used in a Hospital Information System (HIS).


METHODS
The access logs of 3 years of usage of a HIS were analysed concerning report departmental source, type of hospital encounter, and inpatient encounter ICD-9-CM main diagnosis. Reports median life indicates the median time elapsed between information creation and its usage. The models that better explains report views over time were explored.


RESULTS
The number of report views in the study period was 656,583. Fifty two percent of the reports viewed by medical doctors in emergency encounters were from previous encounters - 21% at outpatient attendance, 19% in inpatient (wards) and 12% during emergency encounters. In an inpatient setting, 20% of the reports viewed were produced in previous encounters. The median life of information in documents is 1.5 days for emergency, 4.8 days for inpatient and 37.8 days for outpatient encounters. Immune-hemotherapy reports reach their median lives faster (7 days) than clinical pathology (15 days), gastroenterology (80 days) and pathology (118 days). The median life of reports produced in inpatient encounters varied from 36 days for neoplasms as the main diagnosis to 0.7 days for injury and poisoning. The model with the best fit (R2 > 0.9) was the exponential.


CONCLUSIONS
The usage of past patient information varied significantly according to patient age, type of information, type of hospital encounter and medical cause (main diagnosis) for the encounter. The exponential model is a good fit to model how the reports are seen over time, so the design of user interfaces and repository management algorithms should take it in consideration.
Department of Biostatistics and Medical Informatics, Faculty of Medicine of University of Porto, Al Prof Hernâni Monteiro, 4200-319 Porto, Portugal. ricardo.jc.correia@gmail.com
Ricardo J
RJ
Cruz-Correia
Jeremy C
JC
Wyatt
Mario
M
Dinis-Ribeiro
Altamiro
A
Costa-Pereira
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D005260:Female; D006751:Hospital Information Systems / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D013997:Time Factors; D014584:User-Computer Interface; D055815:Young Adult