A cerebrospinal fluid specimen is sent to the lab at 9:00 P.M. for glucose analysis. The specimen is cloudy and appears to contain red blood cells. Which of the following statements is true?

A cerebrospinal fluid specimen is sent to the lab at 9:00 P.M. for glucose analysis. The specimen is cloudy and appears to contain red blood cells. Which of the following statements is true?

• A. Glucose testing cannot be performed on the specimen.
• B. Specimen should be centrifuged and glucose assayed immediately.
• C. Specimen can be refrigerated as received and glucose assayed the next day.
• D. Specimen can be frozen as received and glucose assayed the next day.

Answer: (B)

Glucose in CSF can be consumed by cells present in the sample after collection, so cellular contamination makes the measured value unreliable if the sample isn’t processed promptly. When CSF is cloudy and contains red blood cells, there are many cells that can metabolize glucose, leading to a falsely low result if you wait to test. Centrifugation removes these cells, giving a cell-free supernatant that can be accurately assayed. Testing immediately after centrifugation stops the glycolytic process from changing the glucose level further, preserving an accurate value. Refrigeration slows glycolysis but doesn’t stop it completely, so waiting until the next day can still yield a lower-than-true result. Freezing isn’t appropriate for routine CSF glucose measurement because it can cause changes that affect the assay. So, centrifuge to remove cells and assay immediately to ensure an accurate glucose reading.

Glucose in CSF can be consumed by cells present in the sample after collection, so cellular contamination makes the measured value unreliable if the sample isn’t processed promptly. When CSF is cloudy and contains red blood cells, there are many cells that can metabolize glucose, leading to a falsely low result if you wait to test.

Centrifugation removes these cells, giving a cell-free supernatant that can be accurately assayed. Testing immediately after centrifugation stops the glycolytic process from changing the glucose level further, preserving an accurate value. Refrigeration slows glycolysis but doesn’t stop it completely, so waiting until the next day can still yield a lower-than-true result. Freezing isn’t appropriate for routine CSF glucose measurement because it can cause changes that affect the assay.

So, centrifuge to remove cells and assay immediately to ensure an accurate glucose reading.