Nurse Judith obtains a specimen of clear nasal drainage from a client with a head injury. Which of the following tests differentiates mucus from cerebrospinal fluid (CSF)?
A. Protein
B. Specific gravity
C. Glucose
D. Microorganism
Correct Answer: C. Glucose
The constituents of CSF are similar to those of blood plasma. An examination for glucose content is done to determine whether a body fluid is a mucus or a CSF. A CSF normally contains glucose. A true normal range cannot be given for CSF glucose. As a general rule, CSF glucose is about two thirds of the serum glucose measured during the preceding two to four hours in a normal adult. This ratio decreases with increasing serum glucose levels. CSF glucose levels generally do not go above 300 mg per dL (16.7 mmol per L) regardless of serum levels.
Option A: Testing for protein would not differentiate mucus from CSF because CSF does not contain protein. CSF protein concentration is one of the most sensitive indicators of pathology within the CNS. Newborn patients have up to 150 mg per dL (1.5 g per L) of protein. The adult range of 18 to 58 mg per dL (0.18 to 0.58 g per L) is reached between six and 12 months of age.
Option B: The specific gravity of CSF at normal body temperature remains between 1.004 and 1.003. Cerebrospinal fluid is alleged to have markedly varied readings: extravagant differences are quoted-1.004 to 1.012, and even greater diversities. If such estimates were arrived at by some form of small hydrometer, or there was delay in testing, or no account was taken of the temperature of the fluid at the moment, then such computed answers were inevitable.
Option D: If microorganisms are found in CSF, this might suggest an infection. Normal CSF may contain up to 5 WBCs per mm3 in adults and 20 WBCs per mm3 in newborns. Eighty-seven percent of patients with bacterial meningitis will have a WBC count higher than 1,000 per mm,3 while 99 percent will have more than 100 per mm3. Having less than 100 WBCs per mm3 is more common in patients with viral meningitis.