Final answer:
A pleural to serum protein ratio of 0.7 indicates an exudate, which is an abnormal fluid accumulation due to conditions causing increased permeability of pleural membranes or decreased lymphatic clearance.
Step-by-step explanation:
In the context of pleural fluid analysis, the ratio of pleural to serum protein is an important diagnostic indicator. A ratio of 0.7 suggests that the pleural fluid has a higher protein content compared to that in the serum, indicating that the fluid is likely an exudate. Exudative effusions are typically associated with conditions that cause increased permeability of pleural membranes or decreased lymphatic clearance, leading to the accumulation of protein-rich fluid in the pleural space. By contrast, a transudate is generally characterized by a lower protein content, reflecting a systemic disorder that affects the hydrostatic or oncotic pressure gradients, without an increase in capillary permeability or decreased lymphatic clearance. Common causes of transudative effusions include congestive heart failure and cirrhosis. Therefore, a pleural to serum protein ratio of 0.7 is indicative of an exudate, which is an abnormal finding and points to a potential underlying disease process that requires further investigation.