Computerized printouts of residents of the Worcester (MA) metropolitan area with healthcare system encounters in which any of 34 ICD-9 diagnosis codes possibly consistent with the occurrence of VTE had been listed in 1999, 2001, and 2003 were obtained from each of the 12 hospitals serving residents of the Worcester Standard Metropolitan Statistical Area (SMSA) [1
]. These data queries were not limited to discharge diagnoses, but also encompassed all outpatient, emergency department, radiology, and laboratory encounters.
The medical records of all identified patients meeting the geographic inclusion criteria (residents of the Worcester SMSA, 2000 census = 477,800) were reviewed [1
]. Trained nurse abstractors using pre-specified criteria performed the validation and characterization of each case of VTE as being definite, probable, possible, or absent [1
]. These criteria were based on a modification of a classification schema proposed by Silverstein et al [2
]. Each case and its classification were also validated by the study project coordinator (CE). If the classification of VTE was not immediately apparent using the diagnostic criteria specified, the medical record was further reviewed by the principal investigator (FS). Incident cases of VTE were defined as those occurring in patients without any prior history of upper or lower extremity DVT or PE. Potential cases of recurrent VTE were classified using similar criteria as that employed for incident cases; the development of a probable or definite recurrence of VTE required the new occurrence of thrombosis in a previously uninvolved venous or pulmonary vessel by ultrasound or radiologic imaging.
Information was collected about patients' demographic characteristics, medical history, clinical characteristics, diagnostic test results, and hospital management practices through review of the medical record. Only medical history variables documented in patients' medical records by a physician were abstracted. The surgery variable included major operations where general or epidural anesthesia lasted 30 minutes or longer. Medical history variables defined as “recent” were those occurring or active in the 3 months prior to the diagnosis of VTE. Major bleeding was defined as any episode of bleeding requiring transfusion or that resulted in subsequent hospitalization, stroke, myocardial infarction, , or death. Subjects were considered to have malignancy-related VTE if they had malignancy (other than basal cell skin cancer) that was being treated or palliated at the time of VTE diagnosis. “Provoked” VTE was defined as VTE occurring within 3 months of hospitalization, major surgery, pregnancy, trauma, or fracture. “Unprovoked” VTE was defined as VTE occurring in the absence of malignancy or any of the above “provoked” variables.
The development of a first recurrence of VTE or a major bleeding episode were determined through the review of subsequent medical records at the same hospital site as the index event as well as through the screening of medical records from the other participating hospital sites. Information about all cause mortality was obtained through hospital record reviews and review of death certificates at the Massachusetts Division of Vital Statistics. Follow-up data were available for a maximum of 3 years.
Incidence rates of initial as well as all episodes of DVT and PE, further stratified according to age, were calculated based on U.S. census estimates of the greater Worcester population in 2000. Differences in the distribution of demographic and clinical characteristics as well as treatment practices in patients further stratified according to age were examined using chi-square tests of statistical significance for categorical variables (Mantel-Haenszel for trend) and ANOVA for continuous variables. Cumulative incidence rates of VTE recurrence, major bleeding, (censoring subjects at the time of death) as well as all-cause mortality were estimated using the life-table method.
Cox regression analyses were constructed in order to evaluate whether age at the time of VTE presentation was associated with our pre-specified outcomes during follow-up including occurrence of recurrent VTE, recurrent VTE manifested as PE, major bleeding, and all-cause mortality. All variables listed in Tables and were included as controlling factors in our regression models. The occurrence of recurrent VTE was included in the analysis of major bleeding as a time-dependent variable in order to assess the impact of this complication on this study outcome. Similarly, the occurrence of major bleeding was included in the analysis of recurrent PE as a time-dependent variable. Finally, the occurrence of new or recurrent PE, any recurrent VTE, and major bleeding were included in our analyses of the relation of age with all-cause mortality.
Clinical Characteristics of Patients with Venous Thromboembolism and Utilization of Diagnostic and Therapeutic Modalities According to Age
Early Treatment of Patients with Venous Thromboembolism According to Age