Immortal Time Bias in Assessing Evidence-Based Care Processes for Staphylococcus aureus Bacteremia

To the Editor The Original Investigation by Goto et al¹ recently published in JAMA Internal Medicine presented the analysis of an impressive data set of 36 868 Staphylococcus aureus bacteremia episodes at Veterans Health Administration hospitals. Goto et al¹ reported that receipt of evidence-based care processes decreased mortality with risk-adjusted odds ratios for mortality of 0.74 (appropriate antibiotics), 0.73 (echocardiography), 0.61 (infectious diseases consultation), and 0.33 (all 3 processes). While these results are striking, we are concerned that immortal time bias has not been properly accounted for in the analysis, which may bias the results in favor of these interventions.