Sputum for RBC

Function

The Sputum for Red Blood Cells (RBC) test is a microscopic examination of expectorated phlegm to detect the presence of occult or visible blood. Under normal physiological conditions, the lower respiratory tract does not leak blood into the airway.

Why it is Ordered

This test is primarily ordered when a patient presents with hemoptysis (coughing up blood) or chronic cough. It helps clinicians differentiate between simple irritation and more severe underlying pathologies. It is a critical tool for identifying early signs of lung tissue erosion or vascular leakage in the pulmonary circuit.

Associated Conditions

The presence of RBCs in sputum is associated with several serious conditions:

• Infectious Diseases: Pulmonary tuberculosis, bacterial pneumonia, and fungal infections (like Aspergillosis) often cause tissue necrosis and bleeding.
• Malignancy: Lung cancer or metastatic tumors can erode bronchial vessels.
• Cardiovascular Issues: Congestive heart failure or mitral stenosis can lead to pulmonary edema where RBCs leak into alveoli.
• Autoimmune Disorders: Wegener's granulomatosis or Goodpasture syndrome.
• Pulmonary Embolism: An infarction in the lung tissue can result in bloody sputum.