Baseline Predictors of Adverse Outcome and Survival in Adults Hospitalized with Invasive Pneumococcal Disease

Invasive pneumococcal disease (IPD) remains associated with substantial mortality. We evaluated whether routinely available baseline variables were associated with 65-day all-cause mortality among adults hospitalized with IPD.

We conducted a retrospective cohort study of 195 adults hospitalized with IPD. The primary endpoint was 65-day all-cause mortality, with hospital admission as the time origin and administrative censoring at day 65. Logistic regression and Cox proportional hazards models were fitted with a prespecified adjustment set that included age, sex, invasive mechanical ventilation, procalcitonin, and pH.

Overall, 42 patients died during follow-up. Non-survivors had lower admission pH, higher procalcitonin concentrations, and more frequent invasive mechanical ventilation. In the adjusted logistic model, lower pH showed a directionally consistent but non-significant association with mortality (OR per 0.05-unit decrease, 1.45; 95% CI, 0.96-2.20; p = 0.080). In the adjusted Cox model, lower pH was associated with a higher mortality hazard (HR per 0.05-unit decrease, 1.31; 95% CI, 1.03-1.65; p = 0.026). When lower pH was correctly oriented as the risk marker, its AUC was 0.729. The apparent AUC of the multivariable model was 0.831, and the bootstrap optimism-corrected AUC was 0.785.

In adults hospitalized with IPD, lower admission pH, higher procalcitonin levels, and invasive mechanical ventilation were associated with worse outcomes. Lower pH showed the most consistent prognostic signal, particularly in time-to-event analysis, but estimates were imprecise and should be interpreted as exploratory. These findings support the potential bedside value of early acid-base assessment for risk stratification in IPD.