Decreasing the Need for CT Pulmonary Angiograms in COVID Positive Patients using D-Dimer Levels

From the 2021 HVPAA National Conference

Marcelle Pignanelli (Flushing Hospital Medical Center), Joseph Monye, Alfonso Slu, Nawal Ahmed, Shahlan Alraddawi, Alma Martini, R Jonathan Robitsek, Karen Beekman

Background

Patients presenting with hypoxia and COVID-19 are at increased risk for pulmonary embolism (PE). Elevated D-dimers are a hallmark feature of severe COVID-19 infection, regardless of presence of PE. Therefore, clinicians tend to obtain CT Pulmonary Angiograms (CTPA) in a significant proportion of patients based on these 2 variables alone. It has been observed that this practice has led to high rates of negative CTPAs. Over-utilization of CTPA increases resource utilization, hospital costs, risks of contrast-induced nephropathy, and chances viral spread during transport.

Objective

The specific aim of this project is to decrease over-utilization of CTPA’s in patients admitted with COVID-19 without negatively impacting patient care, with goal of decreasing negative CTPA’s by 25%.

Methods

This project was completed at a community teaching hospital in a dense, multiethnic area of Queens, NY. We had approximately 60 beds dedicated to COVID-19 patients during the time of this project (January 2021-March 2021).

The initial intervention was to educate clinicians about elevated rates of negative CTPAs in COVID-19 patients and encourage the use of other clinical factors when determining who to send for CTPAs. During interdisciplinary rounds, admitting residents were encouraged to take into account other factors prior to ordering CTPA, including alternative risk factors, Wells Score, D-Dimer levels, and lower extremity doppler results if available. Nurses and respiratory therapists were advised to notify residents of unexplained episodes of desaturation or tachycardia.

Inflammatory markers, including D-Dimer levels, were collected every 48 hours. Thromboprophylaxis was started on all patients with suspected or confirmed COVID-19. Interdisciplinary communication during daily patient rounds.

During this phase of initial intervention, D-dimer values and CTPA results were collected in order to determine a D-dimer value that was sensitive for predicting PE in patients with COVID-19. Patients were excluded if admitted directly to the MICU, younger than 50 years old, or had a negative COVID-19 swab. For the initial phase of our project, presence of venous duplex results were not taken into account.

Results

A total of 68 patients with COVID-19 infection had a CTPA with a corresponding D-dimer value within 48 hours. The median (min, 25th percentile, 75th percentile, max) D-dimer for the group was 2,026 ng/mL (220; 1,193; 4,730; 106,004). CTPA was positive for PE in 11 (16%) patients.

Cut-point analysis to determine the D-dimer level with maximum sensitivity for predicting PE on CTPA revealed a D-dimer of 1,710 ng/mL provided a sensitivity of 1.00 and a specificity of 0.49, with AUC of 0.75. If one had used a cutoff D-dimer value of 1,710 ng/mL to determine which patients would have had a CTPA, 27 (40%) patients would not have undergone a CTPA, and no PE would have been missed.

Conclusions

Over-utilization of CTPA has been observed among COVID positive patients with hypoxia regardless of D-dimer levels. We found that a D-Dimer level of 1,710 ng/mL provided 100% sensitivity and 49% specificity in diagnosis. Our plan over the next 60 days is to validate the results in an independent sample at another institution and to analyze additional factors that could be used to enhance specificity of our results.

Clinical Implications

We believe D-Dimer levels are useful in improving diagnostic efficacy of CTPAs in detecting PEs in COVID positive patients and hope to reduce costs of care for patients while delivering high value care and maintaining their safety.

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