Routine inflammatory–nutritional indices in acute schizophrenia: case–control profiles and longitudinal changes during clinical follow-up

Schizophrenia has been associated with peripheral inflammatory and metabolic changes, but the relative value of routine blood-derived composite indices remains uncertain. We compared eight inflammatory–nutritional indices in 146 patients hospitalized with acute-phase schizophrenia and 146 age- and sex-matched healthy controls; 93 patients underwent repeat blood testing after clinical improvement during routine antipsychotic treatment. After FDR correction, NLR, MLR, PLR, SII, NPAR, and PAR were higher in SCZ, whereas PNI and AAPR were lower. MLR showed the strongest single-index case–control discrimination (AUC, 0.797). Screening all 84 two- and three-index models identified MLR + PNI + AAPR (apparent AUC, 0.854). Selection-aware bootstrap validation yielded an optimism-corrected AUC of 0.839, and the same panel was re-selected in 49.7% of resamples. A sensitivity model using the four underlying laboratory variables directly (monocyte count, lymphocyte count, albumin, and alkaline phosphatase) achieved a slightly higher apparent AUC of 0.867, indicating that the derived ratios offered no discrimination advantage over their components. During follow-up, SII, PAR, and NLR decreased, whereas PNI and AAPR did not change significantly. Exploratory medication analyses showed no FDR-significant difference in biomarker change between monotherapy and combination treatment, and the standardized final-dose ratio was not associated with biomarker change. Because all patients received routine treatment and there was no untreated comparison group, the longitudinal findings are interpreted as changes observed during follow-up rather than direct treatment effects. These indices may add low-cost information to routine blood tests but are not diagnostic tools.