Original ArticlesTwo-Way Referral Bias: Evidence from a Clinical Audit of Lymphoma in a Teaching Hospital
Introduction
“Referral filter bias,” as defined by Sackett [1], occurs when the concentration of rare causes, multiple diagnoses, and “hopeless” cases increases as a group of ill patients are referred from primary to secondary to tertiary care. Published reports from tertiary institutions may thus reflect the consequences of referral rather than an accurate depiction of the distribution of disease or its outcome. Increased disease complexity or severity is often associated with worse outcomes [2]although this has not been reported consistently [3]. We performed a clinical audit on the outcome of lymphoma patients diagnosed and/or treated in our institution and noted that nearly half were from outside of the Jerusalem area. In the Israeli health care system, with its universal coverage under the Health Insurance Law, patients would, as a matter of course, be directed to an institution close to their place of residence by their local Sick Fund. Outside of the Jerusalem area the choice of tertiary institutions, including teaching hospitals, is wide, the closest teaching hospital being approximately 45 kilometers from the city. The decision to send a patient to Hadassah, therefore, would reasonably constitute referral, whether by the physician or the patient him/herself. This report compares demographic and disease characteristics as well as survival between “local”patients and those from outside the Jerusalem district catchment area (hereafter considered “referred”) in an attempt to examine whether significant referral bias occurred.
Section snippets
Subjects and methods
Hadassah University Hospital is a 915-bed teaching hospital situated on two campuses in Jerusalem. It provides care for approximately 70% of lymphoma patients diagnosed in Jerusalem. As part of a general strategy of quality assurance, a clinical audit of outcome of lymphoma patients diagnosed between 1987 and 1992 was carried out. In order to ensure coverage of all lymphoma cases cared for in multiple settings, multiple sources were used to ascertain lymphoma cases who had been cared for in our
Statistical analysis
All analyses were performed using SPSS for Windows (SPSS Inc., Chicago, IL). Survival data were confirmed for all patients non-differentially using the Death Registry of the Ministry of Interior. Survival was measured from date of diagnosis, whether or not the diagnosis was made in Hadassah. Categorical variables were compared using chi-square. Kaplan-Meier survival curves were generated and compared using the log-rank statistic. In the analysis of survival we excluded patients with mycosis
Results
During the period of the audit, 716 patients with a diagnosis of lymphoma were ascertained from the three sources noted above (82% from the hospital ATD computer database). Of these, 399 (56.2%) were Jerusalem district residents (“local”) and 311 (43.8%) lived outside of the city (“referred”). Place of residence was missing for five patients. A comparison of demographic characteristics between these two groups is noted in Table 1. Referred patients were younger (p < 0.0001), were more likely to
Discussion
Our audit revealed that survival for lymphoma patients treated in our institution was comparable to published results from the world literature 6, 7, 8. We have shown significant differences in demographic and clinical characteristics between local and referred patients in our clinical audit of lymphoma in a teaching hospital. Patients who came from a distance, were referred, or chose not to attend their local hospital were younger and were less likely to be immigrants. In addition, they were
Conclusion
We have shown that patients referred to our center for the care of lymphoma are younger but have more aggressive histologies, while their survival may be worse, as good as, or better than local patients. Some, but not all, of the differences between referred and local patients can be accounted for by access to BMT in our institution exclusively. The paradox of increased complexity of referred patients yet equivalent or improved survival corresponds to findings in the literature. Since place of
Acknowledgements
The authors gratefully acknowledge the assistance of Lois Gordon in the preparation of the figures.
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