Using probability vs. nonprobability sampling to identify hard-to-access participants for health-related research: costs and contrasts.

This article compares the recruitment costs and participant characteristics associated with the use of probability and nonprobability sampling strategies in a longitudinal study of older hemodialysis patients and their spouses. Contrasts were made of people who accrued to the study based on probability and nonprobability sampling strategies. Probability-based sampling was more time-efficient and cost-effective than nonprobability sampling. There were no significant differences between the respondents identified through probability and nonprobability sampling on age, gender, years married, education, work status, and professional job status. Respondents from the probability sample were more likely to be Protestant and less likely to be Catholic than those from the nonprobability sample. Respondents from the probability sample were more likely to be Black, whereas those from the nonprobability sample were more likely to be White. There are strengths and shortcomings associated with both nonprobability and probability sampling. Researchers need to consider representativeness and external validity issues when designing sampling and related recruitment plans for health-related research.

Predictors of patient treatment preferences and spouse substituted judgments: the case of dialysis continuation.

OBJECTIVES: To examine the factors predicting preferences for continued hemodialysis treatment among patients with endstage renal disease (ESRD) and to compare these factors to those predicting their spouses' predictions of patients' preferences (substituted judgments). DESIGN: Descriptive, cross-sectional. PARTICIPANTS: Total of 291 hemodialysis patients, aged 55 years and older, and their spouses. MEASUREMENT: Hypothetical scenarios were designed to elicit preferences for dialysis continuation under various health conditions. Other measures included the Philadelphia Geriatric Center Negative Affect Scale, Kidney Disease Symptoms Scale, Brief Multidimensional Measure of Religiousness, single-item global subjective health and quality-of-life measures, 2-item fear of end-of-life suffering measure, and selected demographics. RESULTS: Patients' preferences and spouses' judgments were only moderately correlated (r = 0.33). Multiple regression analyses revealed that patients' preferences to continue dialysis were positively related to education, subjective quality of life, and religious participation and negatively related to months of ESRD treatment and fear of end-of-life suffering (R(2) = 0.15). Spouses' substituted judgments regarding patients' dialysis continuation preferences were positively related to African American race and spouses' perceptions of patients' quality of life and negatively related to months of ESRD treatment, spouses' perception of patients' negative affect, and spouses' own fear of end-of-life suffering. CONCLUSION: Patients and surrogates used different criteria in formulating judgments about continuation of life-sustaining treatment and had different perceptions about the patients' condition. Furthermore, the substituted judgments of spouses were influenced by their own characteristics. These processes may explain inaccurate substituted judgments.

Spouse as health care proxy for dialysis patients: whose preferences matter?

PURPOSE: We examined the extent to which the substituted judgments made by spouses of patients with end-stage renal disease actually reflect patient preferences. DESIGN AND METHODS: We used data from 291 couples to compare dialysis patients' preferences for continuing hemodialysis under a variety of hypothetical situations with both substituted judgment data from spouses and information about spouses' own preferences. RESULTS: Substituted judgments were more highly related to spouses' preferences than to patients' preferences. IMPLICATIONS: Findings raise questions about the extent to which the moral principle of patient autonomy should guide decision making at the end of life.