Can pneumonia always be diagnosed by auscultation (listening with a stethoscope)?

From the Guidelines

No, pneumonia cannot always be diagnosed by auscultation alone, as abnormal breath sounds may be absent in up to 30% of patients with confirmed pneumonia. The diagnosis of pneumonia should rely on a comprehensive approach, including clinical history, physical examination, laboratory tests, and imaging studies. According to the most recent and highest quality study 1, the absence of runny nose and presence of breathlessness, crackles, and/or diminished breath sounds on auscultation, tachycardia, and fever (38C or greater) is suggestive of pneumonia. However, the quality of evidence is low, and a comprehensive approach is necessary to confirm the diagnosis.

Some key points to consider in the diagnosis of pneumonia include:

• Clinical symptoms and signs, such as cough, dyspnea, pleural pain, sweating/fevers/shivers, aches and pains, temperature 38C or greater, tachypnea, and new and localizing chest examination signs 1
• Laboratory tests, such as C-reactive protein (CRP), which can strengthen the diagnosis and exclusion of pneumonia 1
• Imaging studies, such as chest radiography, which can improve diagnostic accuracy, especially in patients with abnormal vital signs 1
• The importance of considering patient factors, such as obesity, shallow breathing, dehydration, early-stage infection, or pneumonia located in areas not easily accessible by stethoscope, which can make lung sounds difficult to detect

It is also important to note that some patients, particularly elderly individuals or those who are immunocompromised, may present with atypical symptoms lacking the classic respiratory signs. Therefore, a comprehensive approach to diagnosis is crucial to ensure accurate diagnosis and treatment of pneumonia. As stated in 1, a demonstrable infiltrate by chest radiograph or other imaging technique, with or without supporting microbiological data, is required for the diagnosis of pneumonia.

From the Research

Diagnosis of Pneumonia using Auscultation

• Pneumonia cannot always be diagnosed by auscultation (listening with a stethoscope) alone, as the physical examination of the lungs has a poor interobserver agreement due to lack of standardisation in the findings 2.
• The use of an electronic stethoscope with computerised analysis of the lung sounds might improve diagnostic accuracy, but there are no physical diagnostic findings that have a very high predictive value for pneumonia 2.
• Abnormal findings on lung examination, such as rales, rhonchi, decreased breath sounds, wheezes, altered fremitus, egophony, and percussion dullness, were each found in fewer than half of the patients with pneumonia, and 22% of patients with a completely normal chest examination had pneumonia 3.
• The presence of fine and coarse crackles detected patients with ground-glass opacities with a sensitivity of 84.6% and specificity of 12.5%, while the presence of Velcro crackles identified patients with ground-glass opacities with a sensitivity of 41% and specificity of 81.3% 4.
• Electronic auscultation is useful to aid diagnosis and timely management of COVID-19 pneumonia, but further studies are indicated to validate the accuracy and potential clinical benefit of auscultation in detecting pulmonary abnormalities in COVID-19 infection 4.

Limitations of Auscultation

• No single symptom or sign is reliably predictive of pneumonia, and cough was the most common symptom in patients with pneumonia, but was equally common in those with other respiratory illness 3.
• Fever was absent in 31% of patients with pneumonia, and abnormal vital signs were 97% sensitive for the detection of pneumonia 3.
• The diagnostic value of serum C-reactive protein (CRP) for identifying pneumonia in hospitalized patients with acute respiratory symptoms is useful, with CRP intervals above 200 mg/L associated with a high likelihood of pneumonia, and CRP intervals below 75 mg/L associated with a low likelihood of pneumonia 5.