Intravenous immunoglobulin for severe sepsis and septic shock: clinical effectiveness, cost-effectiveness and value of a further randomised controlled trial

Table 2 Evidence on the clinical effectiveness of IVIG for severe sepsis/septic shock: estimates from the best-fitting models for the synthesis of evidence

Model for the synthesis of clinical effectiveness evidence	Odds ratio (95% CrI)
M1: Fixed-effect model considering three treatments: IVIG/IVIGAM vs. albumin vs. no treatment, with covariate on duration of IVIG therapy. Relative effectiveness estimate reported for IVIG/IVIGAM vs. albumin for a duration of therapy of three days.	0.75 (0.58, 0.96)
M2: Random-effects model considering three treatments: IVIG/IVIGAM vs. albumin vs. no treatment, no covariates. Relative effectiveness estimate reported for IVIG/IVIGAM vs. albumin.	0.68 (0.16, 1.83)
M3: Random-effects model considering two treatments: IVIG/IVIGAM vs. albumin or no treatment, with covariate on Jadad score. Relative effectiveness estimate reported assuming a Jadad score of 5.	0.83 (0.18, 2.13)
M4a: Random-effects model considering two treatments: IVIG/IVIGAM vs. albumin/no treatment, with covariate representing $1 / \sqrt{N}$ . Relative effectiveness estimate reported assuming a sample size of 339 patients^*	0.92 (0.23, 2.10)
M4b: Random-effects model considering two treatments: IVIG or IVIGAM vs. albumin or no treatment, with covariates representing $1 / \sqrt{N}$ . Relative effectiveness estimate assumes an infinitely large sample size^*	1.27 (0.25, 3.17)

^*With model M4 two cases were considered: for M4a, the sample size N was set equal to the maximum arm size in the studies in our review - avoiding extrapolation beyond the dataset; for M4b, sample size was set to infinity; this demonstrates the effect on model estimates of the absence of bias associated with study quality, here proxied by finite (and small) sample sizes. CrI, credible interval, the Bayesian equivalent to confidence intervals; IVIG, intravenous immunoglobulin; IVIGAM, immunoglobulin M-enriched polyclonal IVIG.

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