Admission prognostic nutritional index improves risk stratification for the carbapenem-resistant phenotype in culture-positive Klebsiella pneumoniae: a retrospective cohort study.

BACKGROUND: Carbapenem-resistant Klebsiella pneumoniae (CRKP) remains an infection-control challenge. We assessed whether admission immuno-nutritional status, measured by the Prognostic Nutritional Index (PNI), is associated with the CRKP phenotype and adds risk information beyond clinical exposures. METHODS: We conducted a retrospective cohort study at Wanbei Coal Electricity Group General Hospital, China (2020-2025). Among 2,571 inpatients with a positive K. pneumoniae culture, 1,360 adults with a first positive culture obtained >48 hours after admission were included and chronologically divided into a derivation cohort (n=987) and a temporal internal validation cohort (n=373). PNI was calculated from laboratory tests obtained within 24 hours of admission. The intended prediction window was after K. pneumoniae identification from the index culture but before antimicrobial susceptibility results were finalized; all predictors were restricted to information available by the index specimen-collection date. CRKP was defined as non-susceptibility to at least one carbapenem. Multivariable logistic regression was used for model development, and performance was assessed by area under the curve (AUC), calibration, and reclassification indices. RESULTS: In the derivation cohort, 408 patients (41.3%) had the CRKP phenotype. Lower admission PNI was independently associated with CRKP (adjusted odds ratio [OR] 0.97 per 1-point increase; 95% confidence interval [CI] 0.96-0.98; P < 0.001). Adding PNI to the clinical model increased AUC from 0.690 to 0.708 in the derivation cohort and from 0.682 to 0.700 in the temporal internal validation cohort. Reclassification also improved (NRI 0.230 [95% CI 0.130-0.352]; IDI 0.014 [95% CI 0.005-0.028]). Observed CRKP proportions were 20.4%, 45.9%, and 65.6% across descriptive low-, intermediate-, and high-risk tiers. In an extended sensitivity model adjusting for admission-to-culture interval and specimen source, PNI remained independently associated with CRKP. CONCLUSIONS: Admission PNI was independently associated with the CRKP phenotype and provided modest incremental risk information among adults with hospital-onset, culture-positive K. pneumoniae. The model is descriptive and hypothesis-generating and requires external validation before clinical use.