Background: COVID-19 presents with a wide variety of symptoms which also vary in severity. Clinical gestalt is required to help distinguish between COVID-19 and other viral illness. As the pandemic heads into the second year, patient compliance with isolation and quarantine precautions is starting to diminish. The COVID-19 Pretest Probability Calculator is proposed to help offer pre-test probability of COVID-19 to assist in medical decision making.
Methods: Patient’s presenting with COVID-19 like illness were grouped to high, intermediate, or low pretest probability risk based on total scores from reported criteria, which was correlated with the resulting SARS-CoV-2 PCR nasal swab. The calculator was applied in both a prospective and retrospective fashion.
Results: A total of 412 patients were recorded, with a total of 132 positive results. Of low-risk patients, only one patient resulted as positive, while 85% or 111 of total positive results being categorized as high-risk. Overall demonstrated sensitivity was 99% with 50% specificity. Individual criteria were analyzed with anosmia and dysgeusia being the most significant. These symptoms demonstrated 92% specificity, and no low-risk patients reported these symptoms.
Conclusion: The COVID calculator demonstrates strong rule-out capability for patients who are low risk. Furthermore, 85% of positive patients were high risk which suggests the need for longer isolation or retesting especially when an alternative diagnosis cannot be established. If a patient reports anosmia or dysgeusia a higher index of suspicion for COVID-19 should be considered.