The role of matched controls in building an evidence base for hospital-avoidance schemes: a retrospective evaluation.

OBJECTIVE

To test whether two hospital-avoidance interventions altered rates of hospital use: "intermediate care" and "integrated care teams."

DATA SOURCES/STUDY SETTING: Linked administrative data for England covering the period 2004 to 2009.

STUDY DESIGN

This study was commissioned after the interventions had been in place for several years. We developed a method based on retrospective analysis of person-level data comparing health care use of participants with that of prognostically matched controls.

DATA COLLECTION/EXTRACTION METHODS: Individuals were linked to administrative datasets through a trusted intermediary and a unique patient identifier.

PRINCIPAL FINDINGS

Participants who received the intermediate care intervention showed higher rates of unscheduled hospital admission than matched controls, whereas recipients of the integrated care team intervention showed no difference. Both intervention groups showed higher rates of mortality than did their matched controls.

CONCLUSIONS

These are potentially powerful techniques for assessing impacts on hospital activity. Neither intervention reduced admission rates. Although our analysis of hospital utilization controlled for a wide range of observable characteristics, the difference in mortality rates suggests that some residual confounding is likely. Evaluation is constrained when performed retrospectively, and careful interpretation is needed.