Day 3 Blood Urea Nitrogen and Discharge Disposition in Patients With Pleural Infection: A Multicenter Prospective Study

Background: Although the RAPID score is a validated predictor of mortality in pleural infection, the prognostic value of laboratory measurements obtained during early treatment remains uncertain. We evaluated whether Day 3 laboratory markers, particularly blood urea nitrogen (BUN), were associated with failure to return to the pre-admission residence or care environment.

Methods: This multicenter prospective observational study included 81 patients with pleural infection across 13 hospitals in Japan. Patients with complete baseline and Day 3 data for BUN, C-reactive protein (CRP), albumin, and creatinine were included in the primary analysis. Multivariable Firth logistic regression models evaluated each Day 3 laboratory marker after adjustment for its corresponding baseline value, age, and Eastern Cooperative Oncology Group (ECOG) performance status. An exploratory sensitivity analysis excluded patients deemed unfit for surgery at baseline. The primary outcome was failure to return to the pre-admission residence or care environment at the end of the index hospitalization.

Results: Among 81 patients, 25 (30.9%) did not return to their pre-admission residence or care environment. Day 3 BUN was not significantly associated with failure to return in the primary analysis (adjusted odds ratio [OR] per 5 mg/dL, 1.12; 95% confidence interval [CI], 0.91–1.47; P=0.302). Day 3 CRP, albumin, and creatinine were also not significantly associated with the outcome. Older age was significantly associated with failure to return in all four models. In the exploratory sensitivity cohort of 70 patients, higher Day 3 BUN was associated with failure to return (adjusted OR per 5 mg/dL, 1.60; 95% CI, 1.08–2.62; P=0.017).

Conclusions: Day 3 BUN and other routinely measured laboratory markers were not significantly associated with discharge disposition in the primary adjusted analysis. The association observed for Day 3 BUN in the restricted sensitivity analysis should be considered hypothesis-generating and requires validation.