Abstract Background Intravenous immunoglobulins (IVIG) have been suggested as an adjunctive treatment in streptococcal toxic shock syndrome (STSS), but there are no conclusive trials. In southern Sweden, IVIG is routinely used in certain hospitals but not in others. We hypothesized that this would resemble a natural experiment, and aimed to evaluate the effect of IVIG in STSS patients. Method We conducted a population-based retrospective cohort study on STSS cases in southern Sweden from 2017 to 2024. The main exposure was any IVIG treatment, and the primary outcome was 30-day mortality. Cox regression, adjusted for lactate, Sequential Organ Failure Assessment score, Charlson Comorbidity Index and concurrent clindamycin treatment, were used. We modelled IVIG as a time-dependent variable to address immortal time bias. Results In total, 106 patients fulfilled STSS criteria, of which 56 (53%) were treated with IVIG. Despite geographical differences, the IVIG group was younger, had fewer comorbidities but higher disease severity at baseline. Crude analysis suggested a lower mortality in the IVIG group (Hazard ratio 0.69, 95% CI: 0.34–1.41). However, after adjusting for covariates and accounting for immortal time bias, the hazard ratio was estimated at 1.69 (95% CI: 0.66–4.30). Conclusion Although our study included a large population of STSS patients, our results were inconclusive regarding the effect of IVIG on 30-day mortality. This study highlights the risk of bias in observational studies in rare conditions. Prospective interventional studies are needed to determine the efficacy of IVIG in patients with STSS.
Wullt et al. (Sun,) studied this question.