Trends in U.S. pneumonia-related admissions among patients with multiple myeloma (2006–2022).

Abstract

e19535 Background: Despite improvements in survival due to novel therapies, patients with multiple myeloma (MM) experience a disproportionate burden of infectious complications. Pneumonia (PNA) is a leading cause of hospitalization and death in this population, but contemporary data describing outcomes and costs of PNA-related admissions (ADMs) are limited. Methods: We conducted a serial cross-sectional study of PNA-related ADMs using the US Healthcare Cost and Utilization Project National Inpatient Sample (HCUP-NIS) from 2006 - 2022. ADMs among adults (≥ 18 years) with and without MM (PNA+MM and PNA-MM) were identified using ICD-9/-10 codes for PNA or MM in any position. National estimates of ADMs were obtained by applying discharge weights provided by HCUP-NIS. Parity between ICD-9 and -10 codes was approximated via general equivalency mapping. Similar cohorts were formed for patients with COVID-19 infection (COVID+MM and COVID-MM) for 2020 - 2022. Endpoints included number of ADMs, in-hospital mortality, length of stay (LOS), and inflation-adjusted median cost (2020 USD). Endpoints were stratified by age, sex, race, income quartile, payer, discharge disposition, and hospital characteristics. The Hospital Frailty Risk Score (HFRS) was used to explore frailty as a predictor of outcomes (2016+). ChatGPT 5.2 (OpenAI) was accessed from 11/2025 - 01/2026 to assist with R code used for cohort formation and data analysis. Study was reviewed and approved by HCUP (01/2025). Results: From 2006 - 2022, 284,450 weighted ADMs in the PNA+MM cohort were identified (mortality: 11.4%, median LOS: 6 days, median cost $48,119). Median cost in the PNA+MM cohort increased from $36,361 to $50,905 while in-hospital mortality decreased from 13.9% to 9.1% from 2006 - 2019. Inflation-adjusted total annual cost in the PNA+MM cohort increased from $855 million to $2.4 billion (181.5%) from 2006 - 2019. From 2006 - 2019, the proportion of PNA+MM ADMs relative to all PNA ADMs increased by 66.4% (r 2 = 0.95, p < 0.001), and the proportion of total costs attributable to PNA+MM ADMs relative to all PNA ADMs increased by 53.9% (r 2 = 0.67, p < 0.001). From 2020 - 2022, 22,935 weighted ADMs were identified in the COVID+MM cohort (mortality: 17.5%, median LOS: 6 days, median cost: $59,032). Compared with non-MM cohorts, the PNA+MM and COVID+MM cohorts were more likely to be older, male, and non-white (p < 0.001). The PNA+MM and COVID+MM cohorts were frailer and displayed higher mortality compared with non-MM cohorts (p < 0.001). Conclusions: PNA-related ADMs among patients with MM are increasingly costly, and there persist demographic and comorbidity-dependent disparities. Study limitations include mid-study change in ICD coding systems and variable clinician coding practices. Research around interventions aimed at reducing admission rates in this population (e.g. antimicrobial prophylaxis, intravenous immunoglobulin, vaccination) is warranted.