To determine risk factors for Clostridioides difficile colonization and C. difficile infection (CDI) among patients admitted to the intensive care unit (ICU).

Retrospective observational cohort study.

Tertiary-care facility.

All adult patients admitted to an ICU from July 1, 2015, to November 6, 2019, who were tested for C. difficile colonization. Patients with CDI were excluded.

Information was collected on patient demographics, comorbidities, laboratory results, and prescriptions. We defined C. difficile colonization as a positive nucleic acid amplification test for C. difficile up to 48 hours before or 24 hours after intensive care unit (ICU) admission without evidence of active infection. We defined active infection as the receipt of an antibiotic whose only indication is the treatment of CDI. The primary outcome measure was the development of CDI up to 30 days after ICU admission. Logistic regression was used to model associations between clinical variables and the development of CDI.

The overall C. difficile colonization rate was 4% and the overall CDI rate was 2%. Risk factors for the development of CDI included C. difficile colonization (aOR, 13.3; 95% CI, 8.3–21.3; P < .0001), increased ICU length of stay (aOR, 1.04; 95% CI, 1.03–1.05; P < .0001), and a history of inflammatory bowel disease (aOR, 3.8; 95% CI, 1.3–11.1; P = .02). Receipt of any antibiotic during the ICU stay was associated with a borderline increased odds of CDI (aOR, 1.9; 95% CI, 1.0–3.4; P = .05).

C. difficile colonization is associated with the development of CDI among ICU patients.

To determine clinical characteristics associated with false-negative severe acute respiratory coronavirus virus 2 (SARS-CoV-2) test results to help inform coronavirus disease 2019 (COVID-19) testing practices in the inpatient setting.

A retrospective observational cohort study.

Tertiary-care facility.

All patients 2 years of age and older tested for SARS-CoV-2 between March 14, 2020, and April 30, 2020, who had at least 2 SARS-CoV-2 reverse-transcriptase polymerase chain reaction tests within 7 days.

The primary outcome measure was a false-negative testing episode, which we defined as an initial negative test followed by a positive test within the subsequent 7 days. Data collected included symptoms, demographics, comorbidities, vital signs, labs, and imaging studies. Logistic regression was used to model associations between clinical variables and false-negative SARS-CoV-2 test results.

Of the 1,009 SARS-CoV-2 test results included in the analysis, 4.0% were false-negative results. In multivariable regression analysis, compared with true-negative test results, false-negative test results were associated with anosmia or ageusia (adjusted odds ratio [aOR], 8.4; 95% confidence interval [CI], 1.4–50.5; P = .02), having had a COVID-19–positive contact (aOR, 10.5; 95% CI, 4.3–25.4; P < .0001), and having an elevated lactate dehydrogenase level (aOR, 3.3; 95% CI, 1.2–9.3; P = .03). Demographics, symptom duration, other laboratory values, and abnormal chest imaging were not significantly associated with false-negative test results in our multivariable analysis.

Clinical features can help predict which patients are more likely to have false-negative SARS-CoV-2 test results.