Baseline quality of life before intensive care: a comparison of patient versus proxy responses

Abstract

Objective: To compare acute lung injury patients' self-reported, retrospective baseline quality of life before their intensive care hospitalization with population norms and retrospective proxy estimates.

Design: Prospective cohort study using the Short Form 36 quality-of-life survey.

Setting: Thirteen intensive care units at four teaching hospitals in Baltimore, Maryland.

Patients: One hundred thirty-six acute lung injury survivors and their designated proxies.

Interventions: Both patients and proxies were asked to estimate patient baseline quality of life before hospital admission using the Short Form 36 survey.

Measurements and main results: Compared with population norms, quality-of-life scores were lower in acute lung injury patients across all eight domains, but the difference was significantly greater than the minimum clinically important difference in only two of eight domains (Physical Role and General Health). The mean paired difference between patient and proxy responses revealed no clinically important difference. However, kappa statistics demonstrated only fair to moderate agreement for all domains. Bland-Altman analysis revealed that, for all domains, proxies tended to overestimate quality of life when patient scores were low and underestimate the quality of life when patient scores were high.

Conclusion: Retrospective assessment of quality of life before hospitalization revealed that acute lung injury patients' scores were consistently lower than population norms, but the magnitude of this difference may not be clinically important. Proxy assessments had only fair to moderate agreement with patient assessments. Across all eight Short Form 36 quality-of-life domains, proxy responses represented an attenuation of patient quality-of-life estimates.

Figure 1. Bland Altman plot for the SF-36 General Health domain

This figure displays the relationship of the patient SF-36 scores to the difference between the patient and proxy scores (i.e. patient minus proxy). The area between the dashed horizontal lines represents a difference of 0 ± the minimum clinically important difference (MCID) for patients with chronic pulmonary disease.(30) Each circle represents one patient-proxy pair. The fitted line represents the linear regression model used to estimate the mean difference in patient and proxy responses as a function of the patient response. The dashed lines surrounding the fitted line represents 95% confidence intervals.