黄色ブドウ球菌菌血症に対するPET-CTの死亡率に対する影響

Positive impact of FDG-PET/CT on Mortality in Patients with Staphylococcus aureus bacteremia explained by immortal time bias 

Clinical infectious diseases,2023 

要点

・7施設でブドウ球菌菌血症に対するPET/CTの影響を解析（観察研究）

・476名中178名でPET/CT使用、多変量解析では0.50(0.34-0.74)の効果

・一方でImmortal time biasで調整の結果、1.00(0.68-1.48)で有意差なし

要約

・2大学・５病院で連続的に18歳以上の1セットブドウ球菌菌血症陽性患者をリクルート（2017-2019）, 全医療施設でPET/CT利用可（必須ではない）, 観察研究

・プライマリアウトカム：90日間全死亡、セカンダリーアウトカム：90日間感染死亡

・476名が対象、178名（37.4%）でPET/CT(90日死亡31% )

・PET/CT使用に伴う単変量解析は0.59(0.41-0.86)。多変量解析で0.50(0.34-0.74)

→不死時間バイアス（Immortal time bias）で調整の結果、1.00(0.68-1.48)で有意差なし

Background: Several studies have suggested that in patients with Staphylococcus aureus bacteremia (SAB) [18F] fluorodeoxyglucose positron emission tomography/computed tomography ([18F]FDG-PET/CT) improves outcome. However, these studies often ignored possible immortal time bias.

Methods: Prospective multicenter cohort study in 2 university and 5 non-university hospitals, including all patients with SAB. [18F]FDG-PET/CT was performed on clinical indication as part of usual care. Primary outcome was 90-day all-cause mortality. Effect of [18F]FDG-PET/CT was modeled with a Cox proportional hazards model using [18F]FDG-PET/CT as a time-varying variable and corrected for confounders for mortality (age, Charlson score, positive follow-up cultures, septic shock, and endocarditis). Secondary outcome was 90-day infection-related mortality (assessed by adjudication committee) using the same analysis. In a subgroup-analysis, we determined the effect of [18F]FDG-PET/CT in patients with high risk of metastatic infection.

Results: Of 476 patients, 178 (37%) underwent [18F]FDG-PET/CT. Day-90 all-cause mortality was 31% (147 patients), and infection-related mortality was 17% (83 patients). The confounder adjusted hazard ratio (aHR) for all-cause mortality was 0.50 (95% confidence interval [CI]: .34-.74) in patients that underwent [18F]FDG-PET/CT. Adjustment for immortal time bias changed the aHR to 1.00 (95% CI .68-1.48). Likewise, after correction for immortal time bias, [18F]FDG-PET/CT had no effect on infection-related mortality (cause specific aHR 1.30 [95% CI .77-2.21]), on all-cause mortality in patients with high-risk SAB (aHR 1.07 (95% CI .63-1.83) or on infection-related mortality in high-risk SAB (aHR for 1.24 [95% CI .67-2.28]).

Conclusions: After adjustment for immortal time bias [18F]FDG-PET/CT was not associated with day-90 all-cause or infection-related mortality in patients with SAB.