Clinical biochemistry: oligoclonal bands: practice question

A Biochemistry question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Biochemistry · Clinical biochemistry: oligoclonal bands

Sample item

A 29-year-old woman has episodes of optic neuritis and sensory loss disseminated in time and space. CSF electrophoresis shows IgG bands that are absent in the paired serum. What does this indicate?

AIntrathecal synthesis of immunoglobulin, as in multiple sclerosisBA loss of the alpha-1 globulin band from alpha-1 antitrypsin deficiencyCA monoclonal plasma cell proliferation in bloodDIncreased permeability of the blood-brain barrier only

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

A. Intrathecal synthesis of immunoglobulin, as in multiple sclerosis

Oligoclonal bands present in CSF but not in serum show IgG made by B cells inside the CNS. They are found in over 90 percent of patients with multiple sclerosis, and are also seen in some CNS infections. A raised IgG index supports the same conclusion.

Option by option

A. Intrathecal synthesis of immunoglobulin, as in multiple sclerosis (correct)
Correct. Bands unique to CSF reflect local production of IgG within the CNS.
B. A loss of the alpha-1 globulin band from alpha-1 antitrypsin deficiency
Loss of the alpha-1 band is a serum protein electrophoresis finding in alpha-1 antitrypsin deficiency.
C. A monoclonal plasma cell proliferation in blood
A monoclonal proliferation would give a single band in serum, not bands restricted to CSF.
D. Increased permeability of the blood-brain barrier only
Barrier breakdown would produce matching bands in serum and CSF.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is A, Intrathecal synthesis of immunoglobulin, as in multiple sclerosis. Oligoclonal bands present in CSF but not in serum show IgG made by B cells inside the CNS.

Why is "A loss of the alpha-1 globulin band from alpha-1 antitrypsin deficien…" not the answer?

Loss of the alpha-1 band is a serum protein electrophoresis finding in alpha-1 antitrypsin deficiency.

Why is "A monoclonal plasma cell proliferation in blood" not the answer?

A monoclonal proliferation would give a single band in serum, not bands restricted to CSF.

Why is "Increased permeability of the blood-brain barrier only" not the answer?

Barrier breakdown would produce matching bands in serum and CSF.

What concept does this question test?

It tests Clinical biochemistry: oligoclonal bands in Biochemistry. They are found in over 90 percent of patients with multiple sclerosis, and are also seen in some CNS infections. A raised IgG index supports the same conclusion.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Clinical biochemistry: oligoclonal bands?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.