Recruiting older people to a randomised controlled dietary intervention trial--how hard can it be?

BACKGROUND: The success of a human intervention trial depends upon the ability to recruit eligible volunteers. Many trials fail because of unrealistic recruitment targets and flawed recruitment strategies. In order to predict recruitment rates accurately, researchers need information on the relative success of various recruitment strategies. Few published trials include such information and the number of participants screened or approached is not always cited. METHODS: This paper will describe in detail the recruitment strategies employed to identify older adults for recruitment to a 6-month randomised controlled dietary intervention trial which aimed to explore the relationship between diet and immune function (The FIT study). The number of people approached and recruited, and the reasons for exclusion, will be discussed. RESULTS: Two hundred and seventeen participants were recruited to the trial. A total of 7,482 letters were sent to potential recruits using names and addresses that had been supplied by local Family (General) Practices. Eight hundred and forty three potential recruits replied to all methods of recruitment (528 from GP letters and 315 from other methods). The eligibility of those who replied was determined using a screening telephone interview, 217 of whom were found to be suitable and agreed to take part in the study. CONCLUSION: The study demonstrates the application of multiple recruitment methods to successfully recruit older people to a randomised controlled trial. The most successful recruitment method was by contacting potential recruits by letter on NHS headed note paper using contacts provided from General Practices. Ninety percent of recruitment was achieved using this method. Adequate recruitment is fundamental to the success of a research project, and appropriate strategies must therefore be adopted in order to identify eligible individuals and achieve recruitment targets.

A MitoTracker Green-based flow cytometric assay for natural killer cell activity: variability, the influence of platelets and a comparison of analytical approaches.

OBJECTIVE: A number of flow cytometric assays for natural killer (NK) cell cytotoxicity have been described, however, the relative merits of analytical approaches and the influence of platelets on measured responses have not been systematically evaluated. Information on the time-dependent variability in measured responses is also limited. MATERIALS AND METHODS: Human peripheral blood mononuclear cells were obtained using Nycoprep 1.077, or Nycoprep 1.077 followed by Nycoprep 1.068 (to remove platelets), and incubated for 3 hours with MitoTracker Green (MTG)-labeled K562 cells. Cells were stained with propidium iodide (PI) and the proportions of viable and nonviable target cells (MTG(+)PI(-), MTG(+)PI(+)) were determined by flow cytometry using quadrant and polygonal region analysis. RESULTS: Platelets inhibited NK cell cytotoxicity and the response was underestimated when the nonviable target cell population was not entirely enclosed within the nonviable target cell (upper right) flow cytometric quadrant. The variability in measured NK cell cytotoxic responses in samples obtained from five individuals on three occasions over a 3-week period was 28%, 24%, 26%, and 37%, and 19%, 23%, 27%, and 32% for the quadrant and region analyses (mean coefficient of variation at effector-to-target cell ratios of 100:1, 50:1, 25:1, and 12.5:1, respectively), and 24% and 20% when data were calculated as the area under the cytotoxic curve (AUCC). CONCLUSION: Polygonal regions and the calculation of data as the AUCC appear to be the best approach. This study will be of value to investigators that are wishing to incorporate an NK cell cytotoxicity assay into their portfolio of experimental techniques.

Improvement in nutritional status reduces the clinical impact of infections in older adults.

OBJECTIVES: To determine the effect of a dietary intervention and micronutrient supplementation on self-reported infections in older adults. DESIGN: A randomized, placebo-controlled intervention trial. SETTING: Community living older people in South Yorkshire, United Kingdom. PARTICIPANTS: Two-hundred seventeen older adults aged 65 to 85. INTERVENTION: Participants were randomized to a dietary intervention, a daily micronutrient supplement, or placebo for 3 months, with a 3-month follow-up. MEASUREMENTS: Self-reported measures of infection were reported over the 6-month study period. Secondary outcome measures were nutritional status, dietary intake, quality of life, and depression. RESULTS: Self-reported measures of infection over the 6-month duration of the study were significantly different between the treatment groups. The number of weeks in which illness affected life and the number of general practitioner and hospital visits were significantly lower in the food and micronutrient groups than in the placebo group. The number of weeks in which symptoms of an infection were described was significantly lower in the food group than the placebo and micronutrient groups. Significant improvements in biomarkers of micronutrient status were achieved in the food and micronutrient groups and showed significantly greater change than observed in the placebo group. Significant improvement in dietary intakes was observed in the food group only. CONCLUSION: Improving dietary intake and micronutrient status reduces the clinical impact of self-reported infections in older adults.