On 2014 Feb 12, Andrea Messori commented:

Co-authors of this Note: Valeria Fadda, Roberta Gatto, Dario Maratea, and Sabrina Trippoli (all from the HTA Unit of Estav in Firenze, Italy)

Relative risk (RR) and risk difference (RD) have different advantages and disadvantages [see Walter (2000) for further discussion]. In the paper by Stidham and co-workers (2014), the analysis focused on the induction of remission is the one endowed with the main therapeutic implications. To better explore this data set (end-point = induction of remission), we have re-analyzed the results from the various trials by using both RR and RD as outcome measures for the meta-analysis. Our results are shown in a figure that can be downloaded from the following link: www.osservatorioinnovazione.net/papers/stidham-reanalysis.pdf .

The analysis based on RDs is advantageous because the outcome measure is an absolute one and permits us to interpret the clinical significance of these findings using the number need to treat.

FIGURE LEGEND: The meta-analysis shown in this figure re-examined the same information previously reported by Stidham et al. (data set: induction of remission). Our figure shows the Forest plot with the values of RR (Panel A) or RD (Panel B) for individual trials (solid square with 95%CIs indicated by horizontal bars) and for some trial subgroups (diamonds in yellow). The pooled rates for the entire data-set are shown as blue diamonds. I² is a measure of heterogeneity. Statistical calculations were performed by the OMA software (Open Meta-Analyst version 4.16.12, Tufts University, U.S., url http://tuftscaes.org/open_meta/). Abbreviations: Ev, number of events; Trt, number of patients receiving treatment.

REFERENCES:

-Stidham RW, Lee TC, Higgins PD, Deshpande AR, Sussman DA, Singal AG, Elmunzer BJ, Saini SD, Vijan S, Waljee AK. Systematic review with network meta-analysis: the efficacy of anti-tumour necrosis factor-alpha agents for the treatment of ulcerative colitis. Aliment Pharmacol Ther. 2014 Feb 9. doi: 10.1111/apt.12644. [Epub ahead of print]

-Walter SD. Choice of effect measure for epidemiological data. J Clin Epidemiol. 2000 Sep; 53(9):931-9.

On 2014 Feb 12, Andrea Messori commented:

Co-authors of this Note: Valeria Fadda, Roberta Gatto, Dario Maratea, and Sabrina Trippoli (all from the HTA Unit of Estav in Firenze, Italy)

Relative risk (RR) and risk difference (RD) have different advantages and disadvantages [see Walter (2000) for further discussion]. In the paper by Stidham and co-workers (2014), the analysis focused on the induction of remission is the one endowed with the main therapeutic implications. To better explore this data set (end-point = induction of remission), we have re-analyzed the results from the various trials by using both RR and RD as outcome measures for the meta-analysis. Our results are shown in a figure that can be downloaded from the following link: www.osservatorioinnovazione.net/papers/stidham-reanalysis.pdf .

The analysis based on RDs is advantageous because the outcome measure is an absolute one and permits us to interpret the clinical significance of these findings using the number need to treat.

FIGURE LEGEND: The meta-analysis shown in this figure re-examined the same information previously reported by Stidham et al. (data set: induction of remission). Our figure shows the Forest plot with the values of RR (Panel A) or RD (Panel B) for individual trials (solid square with 95%CIs indicated by horizontal bars) and for some trial subgroups (diamonds in yellow). The pooled rates for the entire data-set are shown as blue diamonds. I² is a measure of heterogeneity. Statistical calculations were performed by the OMA software (Open Meta-Analyst version 4.16.12, Tufts University, U.S., url http://tuftscaes.org/open_meta/). Abbreviations: Ev, number of events; Trt, number of patients receiving treatment.

REFERENCES:

-Stidham RW, Lee TC, Higgins PD, Deshpande AR, Sussman DA, Singal AG, Elmunzer BJ, Saini SD, Vijan S, Waljee AK. Systematic review with network meta-analysis: the efficacy of anti-tumour necrosis factor-alpha agents for the treatment of ulcerative colitis. Aliment Pharmacol Ther. 2014 Feb 9. doi: 10.1111/apt.12644. [Epub ahead of print]

-Walter SD. Choice of effect measure for epidemiological data. J Clin Epidemiol. 2000 Sep; 53(9):931-9.