Original Article
Telephone vs. mail survey gives different SF-36 quality-of-life scores among cancer survivors

https://doi.org/10.1016/j.jclinepi.2007.11.012Get rights and content

Abstract

Objective

To assess whether SF-36 quality-of-life (QOL) subscale scores varied across two survey modes controlling for cancer type and diagnosis cohort.

Study Design and Setting

Stratified random samples of 720 cancer survivors from six cancer types and three time-since diagnosis cohorts were selected from two state cancer registries. Selected survivors were randomly assigned to mail, telephone, or choice of these for survey administration. This study analyzes completed questionnaires obtained from 140 and 155 survivors who were assigned to telephone and mail, respectively.

Results

A significant multivariate effect for survey mode was noted. Mean levels for each subscale controlling for age and accounting for cancer type were higher for telephone compared to mail respondents; significant differences were noted for vitality, role physical, and mental health. The impact of cancer type on QOL subscales was not significant, and the effect of mode was consistent across cancer type.

Conclusions

Previous findings in mode effects for the SF-36 are reproduced here among cancer survivors who may feel more comfortable revealing physical and emotional deficits via mail rather than by telephone. For cancer survivors, it may be that “social desirability” favors responses implying more functioning be it perceived, mental, or physical.

Introduction

Health-related quality of life (QOL) of persons affected by cancer is a key component of assessing patient satisfaction and recovery. However, the measurement of QOL among cancer survivors may be subject to elements of social desirability [1] that differ from those encountered in surveys of the general population. Survivors may shape responses in the context of their cancer and may be more comfortable expressing functional limitations in physical and mental health in writing as opposed to speaking directly to another person. In particular, survivors may not be willing to openly admit deficits in QOL as it may compromise their perception of what constitutes “successful survivorship.” As cancer survivors move along the survivorship continuum, they may avoid actively thinking about their cancer experience as a means of coping with the challenges of long-term survivorship. Response patterns may also differ by cancer type as each cancer may have a unique set of associated physical and emotional issues.

The impact of survey mode (henceforth referred to as “mode”) of QOL scores is not a new topic in the health literature. Within the last 15 years several studies have examined mode effects on the measurement of QOL including many that have focused on different methods of administering the SF-36, one of the most widely used self-report measures of QOL and health status [2]. In general, these studies have included general population (noncancer) samples and have found that telephone-based administration produces higher SF-36 QOL scores as compared to mailed (written) questionnaires [3], [4], [5]. Such mode effects have also been noted in general population studies using other measures of QOL [6], [7], [8], suggesting this pattern of results is not unique to the SF-36 and likely represents a powerful impact of mode of administration on self-reported health instruments.

Although numerous studies have investigated mode effects in measuring QOL among the general population, such investigations with cancer patients are less prevalent. One study found no differences in a general rating of health for prostate cancer survivors assigned to either telephone interview or self-administered mailed questionnaire, but did find differences for questions relating to factual and subjective ratings of sensitive and nonsensitive topics [9]. More recently, Cheung et al. [8] used a convenience sample of cancer patients to compare written and in-person interview scores of three well-known cancer QOL instruments: the EORTC QLQ-C30, the Functional Assessment of Cancer Therapy-General, and the Functional Living Index-Cancer. The results demonstrated higher mean QOL scores for in-person, as opposed to written/self-administration, for 9 of 10 scales.

The extent to which these mode effects findings would hold in a study of cancer survivors QOL using the SF-36 remains to be seen. The present study extends the evaluation of mode on cancer survivors' QOL using a heterogeneous sample of cancer survivors who were randomly assigned to either mail or telephone administration of the SF-36.

Section snippets

Design

This study makes use of data from an implementation pilot initiated by the Behavioral Research Center of the American Cancer Society prior to launching the Study of Cancer Survivors-II—a national study of QOL among cancer survivors. Additional details of the rationale, design, and implementation of the American Cancer Society's Studies of Cancer Survivors as well as the implementation pilot are provided elsewhere [10], [11], [12].

For the implementation pilot, a total of 720 survivors were

Patient characteristics

The overall analytic sample for this study consisted of 155 questionnaire respondents and 140 telephone respondents. The mode of assignment and completion were consistent for these 295 survivors. Demographic and medical characteristics of the survivors included in our analytic sample are provided in Table 1. The distribution of the demographic/medical variables was homogeneous across mode, as expected by the randomization design, with one major exception, retirement status and one minor

Discussion

This study focused on determining whether the subscales of the SF-36 differ across telephone and mail modes for a random sample of cancer survivors selected from two state population cancer registries across three diagnosis-year cohorts. The SF-36 subscales were reliable for each mode. Floor and ceiling effects were relatively consistent with studies that used a similar randomization scheme [22], [24]. Assumptions of the MANCOVA model proved tenable and only one multivariate outlier was

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