Background

• Opportunistic infections (OIs) are recognized complications of chimeric antigen receptor T-cell (CAR-T) therapy.
• Published data are largely single-center or longitudinal cohorts; national admission-level estimates are limited.

Objective
To estimate the incidence, predictors, and inpatient impact of opportunistic infections during adult CAR-T hospitalizations in the United States.

Methods

• Design: retrospective cross-sectional study of the HCUP National Inpatient Sample, 2018-2022 (US inpatient hospitals).
• Adult CAR-T admissions identified using ICD-10-PCS procedure codes.
• OIs defined using ICD-10-CM codes for Pneumocystis jirovecii pneumonia, herpes simplex virus, cytomegalovirus, fungal infections, toxoplasmosis, nocardiosis, and zoster.
• Rare components with unweighted cell size 10 or fewer were aggregated or suppressed.
• Survey-weighted analyses incorporated strata, cluster, and discharge weights.
• Multivariable logistic and linear regression evaluated OI predictors and associations with inpatient mortality, length of stay, and total charges.
• De-identified administrative data were used; informed consent was not applicable.

Limitations

• Administrative coding cannot confirm severity, laboratory values, or treatment intent.
• The NIS counts admissions, not unique patients; no outpatient or post-discharge follow-up.
• Product type, lymphodepletion, and prophylaxis regimens are not captured.

Findings

• 12,980 | Weighted CAR-T admissions (2,596 unweighted)
• 5.4% | Strict OI incidence (broad definition, 10.8%)
• 1,425 to 4,475 | Weighted CAR-T admissions, 2018 to 2022
• 3.50 | Adjusted odds of in-hospital mortality with OI

Outcomes (table: Outcome / OI / No OI)
In-hospital mortality 8.7% vs 2.9% · Length of stay, days 32.4 vs 16.9 · Total charges $1.57M vs $1.15M
Strict OI definition. Linear time trend in strict OI incidence was not significant (OR per year 0.94; P=.259).

Adjusted (table: Variable / Estimate, 95% CI)
Hispanic OR 2.01 (1.17-3.45) · Other/Asian/Native OR 2.25 (1.31-3.89) · Medicaid payer OR 2.49 (1.22-5.09) · Mortality with OI aOR 3.50 (1.76-6.98) · Length of stay +15.5 d (11.1-20.0) · Total charges +$457,196
Charges +$457,196 (95% CI $268,552-$645,840).

Figure caption
Broad definition adds candidiasis. Rare components were aggregated or suppressed per HCUP cell-size rules.

Conclusions
Opportunistic infections complicate a meaningful minority of adult CAR-T hospitalizations and are associated with substantially higher inpatient mortality and resource utilization. Observed differences by race/ethnicity and payer warrant validation in longitudinal post-CAR-T datasets.