Fluid Glucose

Function

Fluid Glucose testing measures the level of sugar in body fluids other than blood, most commonly Cerebrospinal Fluid (CSF), pleural fluid (around the lungs), or peritoneal fluid (in the abdomen). Glucose enters these fluids by diffusion from the blood. In healthy states, fluid glucose levels are typically proportional to blood glucose levels. However, certain pathological processes, particularly infections and cancers, can rapidly consume this glucose, leading to abnormally low levels in the fluid.

Why it is Ordered

This test is vital for differential diagnosis in several scenarios:

• Meningitis Differentiation: In CSF, low glucose (hypoglycorrhachia) strongly suggests bacterial or fungal meningitis, whereas viral meningitis usually presents with normal glucose.
• Pleural Effusion Analysis: Helps distinguish between transudates and exudates. Very low glucose in pleural fluid can indicate rheumatoid arthritis or empyema.
• Peritonitis: Used to assess for bacterial infection in the abdominal cavity.

Associated Conditions

• Bacterial Meningitis: Massive consumption of glucose by bacteria and white blood cells.
• Empyema: A collection of pus in the pleural space.
• Rheumatoid Pleurisy: Characterized by extremely low glucose (often < 30 mg/dL).
• Malignant Effusions: Cancer cells consuming glucose for rapid growth.