RESUMEN
BACKGROUND: Studies that have relied exclusively on web-based surveys to secure follow-up have yielded inadequate follow-up rates, resulting in the need to explore whether supplementing with other methods results in incremental improvements. The primary purpose of this study was to determine the effectiveness of each follow up strategy that was used to collect the follow up data in our ongoing Prevention of Low Back Pain in the Military (POLM) trial. METHODS: This study represents a secondary analysis of the POLM trial. Twenty companies of Soldiers (N=4,325) were cluster randomized to complete one of four exercise programs. Since web-based response rates were lower than anticipated, a telephone call center was established to contact Soldiers who had not responded to the web-based survey. A military healthcare utilization database (M2) was also used to capture additional follow-up. Descriptive statistics and pairwise comparisons were performed to determine the incremental benefits of supplementing the primary web-based follow-up strategy in our ongoing POLM trial and determine whether differences existed in demographic characteristics, pain intensity, and low back pain incidence based on follow-up strategy. RESULTS: Of the 4,325 Soldiers who were enrolled, 632 (14.6%) subjects completed the monthly web-based survey only; 571 (13.2%) responded only to the telephone call; and 233 (5.4%) responded to both the web-based and telephone survey. Adding the telephone call center contributed 804 unique contributions to follow-up, increasing the overall follow-up to 33.2% (n=1,436) and resulting in a net 18.6% increase in follow-up rate. Querying the M2 database yielded follow-up data for an additional 2,788 Soldiers, increasing the follow-up rate by 64.5%. This rate, combined with the web-based and telephone strategies, resulted in an overall follow-up rate of 97.7%. Compared to the web-based survey, those who responded to the telephone call center tended to be younger, white, have a lower income, more likely to smoke, more likely to exercise regularly, and less likely to have low back pain (all with P<.05). CONCLUSIONS: The results of this study can inform the design of future clinical trials by establishing the benefit of supplementing a web-based survey with a telephone call center to secure additional follow-up.