The impact of follow-up blood cultures on mortality and management in patients with gram-negative bloodstream infections: a validation cohort study

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BACKGROUND: The practice of obtaining follow-up blood cultures (FUBCs) in patients with gram-negative bloodstream infections (GN-BSI) remains controversial. The current study had two goals: (1) to internally validate our earlier findings of decreased mortality in patients with FUBCs and increased mortality in those with persistent GN-BSI, and (2) to identify mechanisms by which FUBCs might impact clinical care and outcome. METHODS: Adults with GN-BSI at Duke University were enrolled from 2015 to 2021. Cox proportional hazards models with propensity score-weighting were used to examine associations of FUBCs and positive FUBCs with attributable and all-cause in-hospital mortality. Immortal time bias was addressed by treating FUBCs as a time-dependent variable and through sensitivity analyses. To understand the potential impact of FUBCs on clinical care, matched cohorts were generated (n = 41 in each group): (1) no FUBCs, (2) FUBCs negative for growth, and (3) FUBCs positive for growth (i.e., persistent GN-BSI). Infection-related consultations, imaging studies, and procedures were determined for each matched cohort. RESULTS: Of the 1291 patients in this study, FUBCs were obtained in 78% (1012 patients) and positive in 20% (199 patients). After adjusting for immortal time bias, obtaining FUBCs remained associated with decreased attributable mortality (Hazard ratio [HR] 0.39; 95% confidence interval [CI] 0.32-0.49; p < 0.0001). Persistent GN-BSI was associated with increased attributable mortality (HR 1.77; 95% CI, 1.24-2.52; p = 0.002). Obtaining FUBCs was associated with subsequent infectious diseases (ID) consultation (No FUBCs: 2/41 [5%]; FUBCs: 21/82 [26%]; p < 0.0001). This finding was primarily due to patients with persistent GN-BSI (FUBCs negative: 6/41 [15%]; FUBCs positive: 15/41 [37%]; p = 0.04). Patients with persistent GN-BSI had a higher rate of source control procedures (FUBCs positive: 12/41 [29%]; All others: 11/82 [13%]); p = 0.05). CONCLUSIONS: Obtaining FUBCs was associated with decreased mortality. This mortality effect could stem from increased ID consults after FUBCs and increased source control procedures following positive FUBCs.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.