COVID-19 Diagnosis and Differentiation

Common Symptoms

Fever is present in 92.8% of patients, typically the most common symptom, according to the International Journal of Surgery 1, 2, 3
Cough is present in 69.8% of patients, typically dry in nature, as reported by the International Journal of Surgery 1, 2, 3
Dyspnea or shortness of breath is associated with severe COVID-19, with an odds ratio of 2.43, as found by the International Journal of Surgery 1, 2
Sudden gustatory dysfunction or ageusia is present in 88.8% of patients, and sudden olfactory dysfunction or anosmia is present in 85.6% of patients, which are stronger predictors of COVID-19 than self-reported fever, according to the International Journal of Surgery 1, 2, 3
Fatigue is present in 38.5% of patients, as reported by the International Journal of Surgery 1, 2
Myalgia or muscle pain is present in 27.7% of patients, according to the International Journal of Surgery 1, 2, 3
Headache is present in 7.2% of patients, as found by the International Journal of Surgery 1, 2, 3
Gastrointestinal symptoms, including diarrhea, are present in 6.1% of patients, according to the International Journal of Surgery 1, 2, 3
Sore throat is present in 5.1% of patients, as reported by the International Journal of Surgery 1, 2, 3
Rhinorrhea or runny nose is present in 4.0% of patients, according to the International Journal of Surgery 1, 2, 3

Loss of taste and smell are significantly more common in COVID-19 than influenza, as reported by the International Journal of Surgery 1, 2, 3
COVID-19 shows more diverse CT features, including consolidation patterns 3, and crazy paving pattern 2

Mild cases of COVID-19 (81%) are characterized by non-pneumonia and mild pneumonia, according to the International Journal of Surgery 1, 2
Severe cases of COVID-19 (14%) are characterized by dyspnea, respiratory frequency ≥30/min, blood oxygen saturation ≤93%, PaO2/FiO2 ratio <300, and/or lung infiltrates >50% within 24-48 hours, as reported by the International Journal of Surgery 1, 2
Critical cases of COVID-19 (5%) are characterized by respiratory failure, septic shock, and/or multiple organ dysfunction or failure, according to the International Journal of Surgery 1, 2

Children may present with fever, fatigue, cough, nasal congestion, runny nose, expectoration, diarrhea, and headache, as reported by the International Journal of Surgery 1, 2
Children often have milder clinical presentations than adults, according to the American Society of Anesthesiologists (ASA) 4
Asymptomatic COVID-19 infection is possible, especially in children, as found by the ASA 4 and other studies 5

The American College of Physicians recommends nasopharyngeal swab for RT-PCR as the gold standard for COVID-19 diagnosis, with a sensitivity range of 60-78% 6, 7, 8
The Infectious Diseases Society of America suggests that if initial RT-PCR is negative but symptoms persist or worsen, repeat testing should be considered as false negatives are common, particularly with timing of sample collection relative to symptom onset 9, 8
Antigen testing is labeled for symptomatic individuals within the first 5-14 days of symptom onset, depending on the specific test, and is appropriate for patients with symptoms lasting 3 days 6

The American Heart Association recommends avoiding NSAIDs initially until COVID-19 is ruled out, as there were early concerns about potential worsening of COVID-19 outcomes, although this remains controversial 10
The Centers for Disease Control and Prevention advises that patients should isolate immediately pending COVID-19 test results to prevent potential transmission, and monitor for progression to severe disease 7
Patients with respiratory rate ≥30/min, oxygen saturation ≤93%, or significant dyspnea require urgent re-evaluation 7
The American College of Cardiology recommends re-evaluating patients within 48-72 hours if symptoms worsen or new symptoms develop, particularly shortness of breath, chest pain, or high fever, and considering antipyretics if fever develops >38.5°C 10

The American Academy of Pediatrics notes that children infected with influenza are more likely to exhibit symptoms than adults, with only 6.6% being asymptomatic 11
The American College of Cardiology recommends considering a diagnosis of COVID-19 in patients with mild cases, characterized by non-specific symptoms including fever, cough, sore throat, and malaise without dyspnea or abnormal chest imaging, which accounts for 81% of cases 12
The American College of Cardiology also defines severe COVID-19 cases, which occur in 14% of patients, as those with a respiratory rate ≥30 breaths/min, oxygen saturation ≤93%, or lung infiltrates >50% within 24-48 hours 12

The American Academy of Pediatrics reports that hospitalization rates for influenza are highest in children <5 years, particularly infants <6 months, with 17.8% developing pneumonia, 21.6% requiring ICU admission, and 5.3% requiring mechanical ventilation 11
The American College of Cardiology notes that age >65 years, cardiovascular disease, diabetes, cancer, COPD, hypertension, and male gender are risk factors for severe COVID-19 12, 13

The International Journal of Surgery states that septic shock and multiple organ dysfunction are potential complications of COVID-19 13

The American Academy of Pediatrics warns that co-infection with COVID-19 and influenza is possible and can worsen outcomes 11

The presence of fever plus respiratory symptoms and known COVID-19 exposure within 14 days is an indication for testing, according to the Journal of Microbiology, Immunology and Infection 14
Isolated gastrointestinal symptoms, such as nausea, vomiting, or diarrhea, should not be ignored as they can occur without respiratory symptoms and may precede COVID-19-related symptoms, as reported in Gastroenterology 15