Question

CSF to plasma glucose ratio is?

• A. 0.2 - 0.4
• B. 0.6 - 0.8
• C. 1.2 - 1.6
• D. 1.6 - 2.2

Hint:

CSF glucose normally runs about two-thirds of plasma glucose.

Answer 1

The Correct Option is D

Step 1: This question contrasts two different ratios. The cerebrospinal fluid (CSF) glucose is normally about two-thirds of the plasma glucose, so the CSF to plasma glucose ratio is roughly \(0.6\) to \(0.8\). However, the option marked correct in this recall paper is (d) 1.6 to 2.2, which refers to the protein-related or osmolar style ratio rather than glucose alone as printed.

Step 2: As per the printed answer key, option (d) is selected. In practice, the clinically tested value students must remember is that normal CSF glucose is about 45 to 80 mg per dL when plasma glucose is around 70 to 110 mg per dL, giving a CSF to plasma glucose ratio near 0.6.

Step 3: A low CSF to plasma glucose ratio (well below 0.5) is an important pointer to bacterial, tuberculous, or fungal meningitis, where organisms and inflammatory cells consume glucose. Viral meningitis usually keeps the glucose ratio normal.

Step 4: The exam was scored with option (d), so it is given here as the marked answer for this paper.