Objective. To assess the independent contribution of data sources used for case ascertainment in a clinical audit of the outcome of lymphoma patients in our institution. Design. In the absence of a unified register of lymphoma patients diagnosed and/or treated in our institution, we used an elective approach to case ascertainment. Sources included two internal databases (computerized discharge data for hospitalizations and outpatient oncology database) and one external (Israel Cancer Registry) database. Histologic diagnosis was confirmed by search of on-line pathology files or discharge summaries. Demographic, histologic and survival characteristics were compared among patients identified through each data source. Survival was assessed via record linkage with the Population Registry. Setting. A tertiary care university teaching hospital. Study participants. Seven hundred and twelve patients with lymphoma diagnosed between 1987 and 1992. Results. All three sources contributed independently to the total, with the majority (583 or 82%) via hospitalizations. Overlap among the sources was minimal with only 73 (10.3%) of the patients being common to all three sources. Differences (P< 0.05) in the age distribution, country of birth and population groups (defined by religion) as well as histologic diagnoses among the sources were noted. In addition, survival of those ascertained via the outpatient database was higher than those ascertained from other sources (P=0.02 for Hodgkin's disease) even after controlling for age. Conclusions. The use of multiple data sources for case ascertainment in clinical audit is justified when no patient register exists. The results indicate that use of a single internal data source would have resulted both in an underestimate of the scope of lymphoma in our institution and significant bias in terms of patient characteristics and outcome.
Bibliographical noteFunding Information:
We are greatly indebted to our technical collaborators, to the members of the CERN-SL Division for the excellent performance of the LEP collider, and to the funding agencies for their support in building and operating the DELPHI detector. We acknowledge in particular the support of Austrian Federal Ministry of Science and Traffics, GZ 616.364/2-III/2a/98; FNRS–FWO, Belgium; FINEP, CNPq, CAPES, FUJB and FAPERJ, Brazil; Czech Ministry of Industry and Trade, GA CR 202/96/0450 and GA AVCR A1010521; Danish Natural Research Council; Commission of the European Communities (DG XII); Direction des Sciences de la Matière, CEA, France; Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie, Germany; General Secretariat for Research and Technology, Greece; National Science Foundation (NWO) and Foundation for Research on Matter (FOM), The Netherlands; Norwegian Research Council; State Committee for Scientific Research, Poland, 2P03B06015, 2P03B1116 and SPUB/P03/178/98; JNICT-Junta Nacional de Investigação Cientı́fica e Tecnológica, Portugal; Vedecka grantova agentura MS SR, Slovakia, Nr. 95/5195/134; Ministry of Science and Technology of the Republic of Slovenia; CICYT, Spain, AEN96-1661 and AEN96-1681; The Swedish Natural Science Research Council; Particle Physics and Astronomy Research Council, UK; Department of Energy, USA, DE-FG02-94ER40817.
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