Influenza Diagnosis: Symptoms, Physical Examination, and PCR Testing for Differentiating from Cold

The influenza, an acute respiratory infection caused by the influenza virus, presents a significant diagnostic challenge, especially during high incidence seasons. Accurate identification of influenza is crucial for appropriate patient management and to avoid unnecessary antibiotic use. This article explores the influenza symptoms, the physical examination for influenza, and the complementary tests that can assist in its diagnosis.

Symptoms and Physical Examination

The influenza symptoms typically include fever, cough, sore throat, muscle aches, fatigue, and, in some cases, gastrointestinal symptoms. However, these symptoms can overlap with other respiratory infections, complicating the influenza diagnosis based solely on clinical findings. Evidence suggests that the combination of fever and cough, particularly in patients over 60 years old, significantly increases the probability of influenza [1].

The physical examination for influenza may not be conclusive on its own. While the presence of fever and acute respiratory symptoms may suggest influenza, the absence of fever or nasal congestion may decrease the likelihood of influenza [2].

Complementary Tests

Rapid diagnostic tests, such as antigen tests, provide results in less than 30 minutes, but their sensitivity is limited. A study found that these tests have a sensitivity ranging from 49% to 84%, which can lead to false negatives [3]. On the other hand, molecular tests, such as influenza PCR, are more accurate and are considered the gold standard for influenza diagnosis [4].

The implementation of rapid tests in the emergency setting has been shown to reduce length of stay and hospitalization rates, underscoring their value in clinical management [5]. However, it is important to consider the epidemiological context and the circulation of the virus in the community to guide the use of these tests [6].

Conclusions

The influenza diagnosis requires a combination of clinical evaluation and complementary tests. While the influenza symptoms and the physical examination for influenza provide valuable clues, molecular tests such as influenza PCR are essential for accurate confirmation. Differentiating between influenza and other respiratory infections, such as the common cold, is fundamental for appropriate patient management and the prevention of complications.

Referencias

• [1] Does this patient have influenza?
• [2] Predictive value of history and physical examination for the diagnosis of community-acquired pneumonia in adults: a literature review
• [3] Diagnostic accuracy of point-of-care tests in acute community-acquired lower respiratory tract infections. A systematic review and meta-analysis
• [4] Influenza point-of-care test in the GP practice and Emergency Department; analytical accuracy and added value
• [5] Implementation of Alere i Influenza A & B point of care test for the diagnosis of influenza in an ED
• [6] The diagnosis and treatment of acute cough in adults

Created 2/1/2025