Accepting critically ill transfer patients: adverse effect on a referral center's outcome and benchmark measures

Ann Intern Med. 2003 Jun 3;138(11):882-90. doi: 10.7326/0003-4819-138-11-200306030-00009.


Background: Common methods of benchmarking clinical performance rarely, if ever, account for admission source and, in particular, the effect of a patient being transferred from one medical center to another. Small biases in comparisons of observed versus expected deaths can substantially affect how high-quality institutions compare with peer hospitals. With the most sophisticated and validated set of case-mix measures available for patients, the intensive care unit is an ideal setting in which to study the effect of a patient's being transferred from another hospital.

Objective: To determine the extent of bias in benchmarking outcomes when performance measures do not account for transfer patients' greater severity of illness.

Design: Prospectively developed cohort study.

Setting: Medical intensive care unit (MICU) at a tertiary care university hospital.

Patients: 4579 consecutive admissions for 4208 patients from 1 January 1994 to 1 April 1998.

Measurements: MICU and hospital lengths of stay, MICU readmission, and hospital mortality rates.

Results: Compared with directly admitted patients, MICU patients transferred from another hospital had significantly higher Acute Physiology Scores at the time of admission and discharge (P = 0.001). Even after full adjustment for case mix and severity of illness, transfer patients had a 38% longer MICU stay (95% CI, 32% to 45%), a 41% longer hospital stay (CI, 34% to 50%), and a 2.2 times greater odds of hospital mortality (CI, 1.7 to 2.8) than directly admitted patients. With identical efficiency and quality, a referral hospital with a 25% MICU transfer rate compared with another with a 0% transfer rate would be penalized by 14 excess deaths per 1000 admissions when a benchmarking program adjusts only for case mix and severity of illness and not for the source of admission.

Conclusions: In a setting with the most thorough diagnostic-based, case-mix adjustment and the most physiologically precise severity-of-illness information, accepting transfer patients can adversely affect efficiency and quality benchmarks. Benchmarking and profiling efforts beyond intensive care units must also recognize and account for this phenomenon; otherwise, referral centers may have an incentive to refuse care for patients who could benefit from being transferred to their facility.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Benchmarking*
  • Critical Illness* / mortality
  • Diagnosis-Related Groups
  • Female
  • Hospital Mortality
  • Hospitals, University / standards*
  • Humans
  • Intensive Care Units / standards
  • Length of Stay
  • Male
  • Middle Aged
  • Outcome Assessment, Health Care*
  • Patient Readmission
  • Patient Transfer*
  • Prospective Studies
  • Selection Bias
  • Severity of Illness Index