The specific gravity of CSF is

Appeared in: UPPSC 2022

Explanation

Cerebrospinal fluid (CSF) is an ultrafiltrate of plasma, and its specific gravity measures its density relative to water.
The normal specific gravity of CSF is slightly denser than water, with a typical range cited as 1.003 to 1.008.
Textbook sources specify the range as 1.006–1.008 (SRC_22834).
Among the given options, 1.005 is the most representative average value within the commonly accepted physiological range, making it the best answer.

Option A: This value is too low and falls outside the normal physiological range for CSF specific gravity. It is closer to the specific gravity of very dilute solutions.
Option B: This value is at the upper limit or slightly above the normal range for CSF specific gravity.
Option D: This value is incorrect as it is less than the specific gravity of pure water (1.000). CSF is denser than water due to dissolved solutes like proteins, glucose, and electrolytes.

Clinical Relevance

Nursing practice connection: Knowing Normal physiological values of Cerebrospinal Fluid (CSF) helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Understanding normal CSF values is crucial for nurses when assisting with lumbar punctures and interpreting lab results, which is essential for diagnosing neurological conditions like meningitis, subarachnoid hemorrhage, and multiple sclerosis.
A nurse observing a CSF lab report with a specific gravity of 1.015, along with other symptoms like fever and nuchal rigidity, should recognize these as potential signs of bacterial meningitis and escalate care promptly.
What if? If the question asked for the normal specific gravity of urine, the answer would be different. Normal urine specific gravity has a much wider range (typically 1.005 to 1.030), reflecting the kidney's ability to concentrate or dilute urine based on the body's hydration status.

How to Approach the Question

This is a factual recall question that tests knowledge of normal physiological values.
First, identify the specific parameter being asked: the specific gravity of cerebrospinal fluid (CSF).
Recall the normal range for this value. The specific gravity of CSF is slightly higher than that of water (1.000).
Evaluate the given options against the known normal range (typically 1.003-1.008).
Eliminate options that are clearly incorrect. 0.98 is less than water, so it can be immediately discarded. 1.001 is too low, and 1.009 is too high for a normal value.
Select the option that best fits within the normal range or represents the accepted average value, which is 1.005.

Concept Tested & Keywords

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E6 Biochemistry U Satyanarayana— Part 2 (pp 421-820 of 840) p. 121-123

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