The CALLY index, a novel composite biomarker, is inversely associated with preserved ratio impaired spirometry (PRISm): A nationally representative cross-sectional study

Preserved ratio impaired spirometry (PRISm) is an intermediate pulmonary phenotype with heightened cardiometabolic risk. Effective tools for its identification are lacking. However, its relationship with systemic inflammatory-nutritional balance is underexplored. The CALLY index integrates C-reactive protein, albumin, and lymphocyte count. This composite biomarker reflects inflammatory-nutritional homeostasis. This study aimed to investigate the association between the ln(CALLY) index and PRISm in a nationally representative U.S. adult population. We analyzed data from 7296 participants in the National Health and Nutrition Examination Survey (NHANES) 2007-2010. PRISm was defined as FEV1/FVC ≥ 0.7 with FEV1 < 80% predicted. Multivariable logistic regression models assessed the association between ln(CALLY) (as quartiles and per-standard-deviation increases) and PRISm, with sequential adjustment for demographic, socioeconomic, and cardiometabolic factors. Restricted cubic splines examined the dose-response relationship. Subgroup and sensitivity analyses evaluated the robustness of findings. Among participants, 920 (12.6%) had PRISm. Compared to those with normal pulmonary function, PRISm individuals had significantly lower ln(CALLY) values (1.21 vs 1.77, P < .001). In fully adjusted models, higher ln(CALLY) quartiles had progressively lower PRISm odds: Q2 (OR = 0.71, 95% CI:0.57-0.88), Q3 (OR = 0.63, 0.47-0.84), and Q4 (OR = 0.48, 0.35-0.66) vs Q1 (P-trend < 0.001). Each standard deviation increase in ln(CALLY) reduced PRISm risk by 24% (OR = 0.76, 0.68-0.85). Restricted cubic spline analysis showed a monotonic inverse linear dose-response relationship (P-overall < .001, P-nonlinear = .707). Subgroup analyses found stronger protective associations in women (P-interaction = .021) and significant heterogeneity across racial/ethnic groups (P-interaction = .036). Sensitivity analyses treating BMI continuously and using multiple imputation supported these findings. Higher ln(CALLY) is independently associated with lower PRISm prevalence in U.S. adults. Systemic inflammatory-nutritional status may be a modifiable risk factor for PRISm, supporting potential targeted prevention strategies. The CALLY index, derived from routine blood tests, could serve as a readily accessible tool for risk stratification of PRISm.