Introduction:
In older inpatients, SARS-CoV-2 positivity does not always indicate that COVID-19 is the cause of admission.

Aim:
To compare clinical profiles and 180-day mortality between older adults admitted for typical COVID-19 and those with incidental SARS-CoV-2 infection.

Material and methods:
This retrospective cohort study included 306 hospitalized patients aged ≥60 years with SARS-CoV-2 infection. Admission phenotype was manually adjudicated as typical COVID-19 respiratory disease or incidental SARS-CoV-2 infection. Baseline characteristics, multimorbidity, CRP, IL-6, D-dimer, SpO2, and 180-day mortality were analyzed. Mortality was assessed using Kaplan–Meier curves and multivariable logistic regression.

Results and discussion:
The cohort included 266 typical and 40 incidental admissions. Multimorbidity was common in both groups (79.2% vs 89.7%; p = 0.122). Typical admissions had lower SpO2 and higher CRP at admission (75.2 vs 34.8 mg/L; p = 0.007), whereas incidental admissions had higher D-dimer concentrations (2.2 vs 1.1 ng/mL; p = 0.016). Crude 180-day mortality was higher in the typical COVID-19 group (42.9% vs 22.5%; p=0.014). After adjustment for age and multimorbidity, incidental phenotype was independently associated with lower mortality odds (OR = 0.40; 95% CI: 0.18–0.89; p = 0.027).

Conclusions:
Typical COVID-19 and incidental SARS-CoV-2 infection are distinct geriatric admission phenotypes. Typical COVID-19 admissions are associated with higher 180-day mortality, independent of baseline multimorbidity.