Randomised controlled trial of intravenous antibiotic treatment for cellulitis at home compared with hospital

Appendix

Table

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Appendix 1

The SF-36 questionnaire was used to measure the degree of change in health status over the course of the study. The questionnaire was completed at baseline and on days three and six. As attention was focused on the physical status of the participants, only those scale items relating to physical health were asked. Transformed scale scores for Physical Functioning, Role Physical and Pain were computed according to the SF-36 instruction manual. The transformation converts the lowest and highest possible scores to 0 and 100, respectively. Scores between these values represent the percentage of the total possible score achieved. A score of 100 indicates perfect health.

A patient’s score at day 0 indicates their prior functioning i.e. their health status before this episode of cellulitis. Table 1 below shows the mean (SD) SF-36 scores in each arm of the trial for days 0,3 and 6. The scores follow the same pattern for patients in each arm – scores are highest at baseline, decrease at day 3 and then show an increase at day 6. This corresponds to the patient feeling relatively well before becoming infected, showing significant deterioration at day 3 and then beginning to improve at day 6 but not quite back to full health.

Because there was so much variability in prior functioning, mean difference scores were calculated between day 0 and day 3, and day 0 and day 6. The two arms of the trial were compared on these difference scores, using t-tests for independent groups. There were no statistically significant mean differences for any of the SF-36 scale scores. The standard deviations for each group are large which indicate the marked variability apparent within each group. There is also much more variability in mean SF-36 scores across time within each arm of the trial than between each arm. This is shown by the relatively small mean difference scores between each arm compared to the differences in mean scores within each arm on each of the days the SF-36 was administered. These results highlight the small differences in health status between the two arms of the trial relative to the larger changes in health status experienced as a consequence of the cellulitis episode. For example, the mean difference between the arms in Physical Functioning on day 6 was 5.2 whereas both groups were still 25 to 30 points below prior functioning.

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Table A: Means (SD) for Days 3 & 6 for SF36 Scale Scores.

⁼Numbers vary due to missing data. Minimum N=86 per group.

⁼⁼⁼A report of health status prior to this cellulitis infection.