Diagnostic Value of Geriatric Nutritional Risk Index and Phase Angle in COPD Malnutrition

Malnutrition prevalence remains a significant concern among hospitalized patients with chronic obstructive pulmonary disease (COPD). Accurate identification of nutritional status is critical for optimizing clinical management and preventing complications associated with poor nutritional intake in this population. This retrospective cohort study aimed to evaluate the diagnostic performance of two biomarkers, phase angle (PhA) and geriatric nutritional risk index (GNRI), for detecting malnutrition in COPD patients.

The research team conducted a single-center analysis involving 121 hospitalized patients with confirmed COPD diagnoses. Participants underwent bioelectrical impedance analysis (BIA) to measure body composition alongside serum albumin measurements. Malnutrition status was classified according to the Global Leadership Initiative on Malnutrition (GLIM) criteria, requiring both available BIA data and valid biochemical parameters for categorization.

Diagnostic efficacy was assessed using receiver operating characteristic (ROC) curves, decision curve analysis (DCA), and bootstrap resampling with 1,000 iterations. The study established preset cutoff values of PhA = 4.25° and GNRI = 98 to evaluate sensitivity, specificity, accuracy, and the K value for each tool against GLIM-defined malnutrition as the reference standard.

Results indicated that GNRI demonstrated superior diagnostic performance compared to phase angle. The geriatric nutritional risk index achieved a sensitivity of 0.753, specificity of 0.700, and accuracy of 0.736 with an AUC of 0.785 (95% CI: 0.699 ~ 0.870). In contrast, phase angle yielded a sensitivity of 0.691, specificity of 0.625, and accuracy of 0.669 with an AUC of 0.656 (95% CI: 0.543 ~ 0.769). The DeLong test confirmed a statistically significant difference in area under the curve between the two tools (p = 0.035).

Decision curve analysis revealed that while net clinical benefits were similar at low thresholds, GNRI maintained positive net clinical benefit across a wider threshold range. Phase angle showed rapidly decreasing net clinical benefits as thresholds increased, eventually turning negative. These findings suggest that GNRI may offer more consistent utility for identifying malnutrition in COPD patients across varying risk profiles.

This study highlights the importance of selecting appropriate biomarkers for nutritional assessment in respiratory disease populations. While both tools demonstrated moderate diagnostic accuracy, GNRI showed greater discriminative power and broader clinical applicability. Researchers should consider these findings when designing nutritional screening protocols for COPD management, though further validation is warranted before routine clinical adoption.