Combining conditional and unconditional recruitment incentives could facilitate telephone tracing in surveys of postpartum women

Abstract

Background and Objective

To compare tracing and contact rates using alternative incentives in a computer-assisted telephone interview (CATI) survey among postpartum women.

Methods

In a randomized trial of 1,061 postpartum women 18–49 years of age selected from four Iowa counties, we compared the effects of: (1) unconditional $5 telephone card incentive enclosed with the introductory letter followed by $25 incentive conditional upon successful telephone tracing, contact, and completion of CATI (Group 1, n = 530) vs. (2) $30 incentive conditional upon subject completion of CATI (Group 2, n = 531).

Results

Overall telephone tracing and contact rates achieved were 67.8% and 66.6%, respectively. Tracing (70.2 vs. 65.4%, P = .09) and contact (68.5 vs. 64.8%, P = .26) rates were consistently higher among subjects assigned the combination of a conditional and an unconditional incentive. The combined incentive type had a greater impact on telephone tracing success rates for subjects on whom we could not initially locate an active telephone number (16.7 vs. 7.3%, P = .07) when compared to subjects for whom we found an active telephone number at the time of mailing the introductory letter (78.9 vs. 75.9%, P = .30).

Conclusions

Combining conditional and unconditional recruitment incentives can facilitate telephone tracing efforts in surveys conducted among recently postpartum women.

Introduction

Recent studies have emphasized trends of decreasing tracing and contact rates in face-to-face interviews [1], telephone and computer-assisted telephone interviews (CATI) [2], [3], [4], [5], [6], [7], [8], [9], [10], [11] as well as mail [10], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24] and internet [25] surveys. Survey recruitment has become so problematic that a Summit, sponsored by the U.S. Census Bureau, was held in 2002. In their final report, the Summit Working Group recommended experimental assessment of unconditional incentives to motivate survey recruitment [26].

Most surveys to date have been conducted among subjects from the general population [1], [2], [3], [4], [7], [8], [9], [10], [18], [20], [21], [22], while others have targeted low-income people [16], students [25], older women [24], and health professionals [6], [12], [13], [14], [15], [17], [19], [23]. Few studies have addressed telephone tracing and contact rates among women of reproductive age or tested the effectiveness of using different incentives to promote recruitment in CATI surveys [27]. Survey topics targeted at women of reproductive age or postpartum women are often of sensitive nature. In addition, women who have recently delivered a new infant are less likely to commit time to a research study due to competing responsibilities. Thus, we expect that results from previous studies may not be applicable to this subgroup of women.

Different methods have been used to enhance tracing and contact rates. Previous research has assessed monetary [1], [6], [10], [12], [13], [14], [15], [16], [17], [18], [20], [21], [23], [24], [25] and nonmonetary [13], [16], [17], [18], [20], [21], [24], [25] incentives or inducements. Some studies have compared a monetary incentive to no incentive [15], [19]. Others have evaluated quantitatively different monetary incentives [6], [12], [16], [20], [23]. Still others have contrasted monetary and nonmonetary incentives [17], [18], [21], [24], [25], conditional and nonconditional incentives [14], as well as the impact of multiple incentives through a factorial design [18], [25].

The aim of the present article is to compare tracing and contact rates achieved by two different incentive protocols among postpartum women. Specifically, the investigators designed this study to determine if tracing and contact rates could be improved by combining an unconditional incentive with a standard conditional incentive already in use, without altering the incentive-associated cost per completed interview. The purpose of an unconditional incentive is to increase the yield of women who would initiate contact with the project coordinating center, irrespective of whether or not they had a telephone. Study subjects were identified from birth certificate records belonging to residents of four Iowa counties, and invited to participate in an epidemiologic CATI survey. We hypothesized that women receiving an unconditional $5 telephone card enclosed with their introductory letter followed by $25 check conditional upon CATI completion (Group 1) would achieve improved rates over women randomized to receive $30 conditional upon CATI completion (Group 2).