Systemic Immune–Inflammation Index and Prognostic Nutritional Index as Predictors of Clinical Outcomes in Chronic Granulomatous Disease: A Retrospective Cohort Study

Chronic granulomatous disease (CGD) is associated with recurrent infections and inflammatory manifestations, which are major contributors to morbidity, hospitalization, and early mortality. Routinely available laboratory parameters obtained during regular outpatient follow-up may facilitate early risk stratification, yet the clinical relevance of systemic inflammatory and nutritional indices in CGD remains incompletely defined. This study examined the associations of the systemic immune–inflammation index (SII) and the prognostic nutritional index (PNI) with selected clinical outcomes in CGD. In this retrospective, single-center cohort study, patients with CGD followed at a tertiary referral center between 1984 and 2025 were included. Outpatient SII (/100) and PNI values were calculated from laboratory data obtained at the first outpatient visit following diagnosis, whereas inpatient values were derived from samples collected during index hospitalization. Associations between these indices and hospitalization status, infectious and non-infectious manifestations, and survival outcomes were evaluated using regression-based and time-to-event analyses. The cohort comprised 74 patients (median age, 19 years); 61 (82.4%) experienced at least one hospitalization and 14 (18.9%) died during follow-up. Higher outpatient SII (/100) values and lower outpatient PNI values were independently associated with hospitalization status, whereas neither index was associated with hospitalization frequency. Inpatient SII (/100) values were higher among non-survivors and demonstrated good discriminative ability for survival status (AUC, 0.806). Higher inpatient SII (/100) and lower inpatient PNI values were associated with shorter overall survival. These findings indicate context-dependent associations, with inpatient indices reflecting survival, while outpatient indices primarily indicate hospitalization susceptibility rather than cumulative disease burden.