This study focuses on sessions and report viewings in the VPR from the last quarter of 2004 to the end of 2007 in HSJ. From the last quarter of 2004 until the end of 2007, the hospital had about 1,583,000 outpatient encounters, 200,000 day-care encounters, 770,000 emergency encounters, 135,000 inpatient encounters and 72,000 emergency consultations adding up to more than 2,760,000 encounters. 977,800 new reports referring to 221,224 distinct patients were collected by the VPR in the same period.
The Health Ethical Commission of the HSJ approved this study (Comissão de Ética de Saúde do HSJ), having the reference number 45/2010.
Procedures for data collection and preparation
The data needed for this study was retrieved from three different Oracle database schemas: (1) the VPR patient database, which included patient identification and the list of clinical documents integrated; (2) the access logs including sessions, health professionals' identification and category and document views; (3) and a hospital encounters database that includes patient identification and the list of encounters since 1993. All sessions from the development team (n = 2,918) in the VPR were excluded from this analysis.
Report views that did not take more than three seconds were considered mistaken views and excluded from this analysis. The VPR is not capable of directly measuring how long reports are viewed, so it was calculated the maximum time of viewing based on the difference between the report request and the following user request on the same session. The number of mistaken views found was 14,972 and represents 2.2% of all views.
Some DIS (especially laboratory IS) send several versions of the same report as new findings occur. In some analysis these different report versions are grouped together to be considered as one single report regardless of version (grouped versions); in others analysis they are considered separately as distinct reports (all versions). The grouped versions method allows to study when does the information inside reports is accessed regardless of the report version, whilst the all versions method allows to study when are files accessed.
All logins are staff numbers generated by the human resources department. In this analysis, the users are identified by their logins.
In the network of the hospital each IP number is associated with the network card's MAC address. In this analysis, each computer is identified by its' network IP number.
Clinical report median life
The clinical report median life is the time it takes to occur half of the views by the users. It is estimated by calculating the median report age (difference between the maximum date of the view and the date of making the report available) within a set of views.
Definition of type of encounter
The VPR system does not know in what context (inpatient, outpatient or emergency) the user is viewing each report. The context was inferred by comparing the date of view and the dates of the different patient encounters. When the date of view matches an encounter, that encounter is associated with the report viewing. When no match is made no assumption is made regarding the encounter.
Concomitant views refer to cases when the medical doctor is viewing a report generated on the present patient encounter (e.g. a doctor asks for a clinical pathology lab exam for an inpatient and the results are seen during that inpatient encounter). Last views refer to cases when the doctor is viewing a report produced on the last encounter whatever its type (e.g. a doctor requests for a imuno-hemotherapy lab exam on an outpatient consultation, and views it in the following outpatient consultation). Previous views refer to views of reports produced previous to the last encounter (e.g. in an emergency encounter the doctor views a report produced 4 encounters ago in an outpatient consultation).
VPR usage analysis
The records were grouped by time periods (quarters) of the date of session start. The views variable refers to all versions of the reports. The number of patient encounters is the sum of all inpatient, outpatient, emergency and hospital day-care encounters occurred in the hospital. Distinct users are calculated by counting the number of different logins that occurred in session logs. The views per user per 10 000 encounters is calculated by . Distinct computers are calculated by counting the number of different IP addresses that occurred in session logs.
Reports' median half analysis
To study the factors that relate to reports' median life, the following variables were studied: patient sex and gender, type of report, hospital encounter related to the report, referral IS and admission and discharge diagnosis in inpatient encounters.
Patient age and gender
Patients are considered as children if their age is 0 to 12 years old, teenager if 13 to 19 years old; young adult if 20 to 34 years old; adult if 35 to 54 years old; old adult if 55 to 69 years old; senior if more than 70 years old). In this case the median life of the grouped versions of the reports was considered.
Type of report
The type of report is determined by the DIS that acts as the VPR feeder system. In the case of immune-haemotherapy the VPR can subdivide them into molecular biology, haemostasis, transfusion laboratory and viral markers since September 2006. In this case the grouped versions of the reports were considered.
Type of hospital encounter
Each report retrieved may be associated with a patient encounter that can be of the following types: inpatient, outpatient, emergency, day-care, radiology and lab result. In this case the grouped versions of the reports were considered, either in the ration of reports viewed and in the median life and dispersion ratio.
Hospital inpatients encounter main diagnosis
The International Classifications of Diseases, 9th revision, Clinical Modification (ICD-9-CM) is based on the official version of the World Health Organisation's 9th Revision, International Classifications of Diseases (ICD-9). ICD-9 is designed for the classification of morbidity and mortality information for statistical purposes and for indexing of hospital records by disease and operations, for data storage and retrieval. In Portuguese hospitals, each inpatient encounter has an ICD-9-CM diagnosis code associated as the main diagnosis of the inpatient encounter. These codes are classified in multi-level hierarchy, and are grouped in chapters, sections and categories. In this analysis the median lives of grouped versions of reports retrieved in inpatient encounters associated with chapters, sections and categories were calculated.
Encounter setting analysis
It was also studied the relation between the types of hospital encounters associated with the creation and view of the reports. This portion of the analysis only takes in consideration visualizations from 2005 and 2006 due to difficulties in accessing detailed data from hospital patient encounters of 2007. All versions of the reports were considered in this analysis.
Median life of reports mathematical model
To obtain a mathematical model, we studied all report views occurring during a 4 months period (September to December 2007). This included reports created before September 2007 and during the studied period. For each of these months the views were grouped according to the age of the reports (e.g. views of report that were one month old, two moths old, and so on, until 44 months old). Then the cumulative frequency was obtained and used to calculate the cumulative percentage of views. These values were then used to obtain logarithmic and exponential trend lines.