The Reiber diagram is a graphical tool designed to analyze the behavior of immunoglobulins (IgG, IgA or IgM) in the cerebrospinal fluid (CSF) and distinguish whether its presence is due to a intrathecal synthesis (within the central nervous system) or to a blood-brain barrier dysfunction.
It was developed by Helmut Reiber and is based on the quantitative analysis of two ratios:
- QIgG: IgG quotient = [IgG_CSF] / [IgG_serum]
- QAlb: Albumin quotient = [CSF_Albumin] / [Serum_Albumin]
(the latter is an indirect indicator of the integrity of the blood-brain barrier).
🧠What does the graph represent?
The x axis shows QAlb (degree of blood-brain barrier dysfunction), and the Y axis shows QIgG (relative amount of IgG in the CSF). Three zones are drawn on the graph:
- 🔹 Normal Zone:
- QIgG and QAlb values ​​within the physiological range.
- There is no evidence of intrathecal synthesis or barrier dysfunction.
- 🟦 Barrier dysfunction zone:
- Parallel increase in IgG and albumin.
- It is interpreted as passive filtration from the serum due to alteration of the blood-brain barrier.
- 🟥 Intrathecal synthesis zone:
- QIgG is blown out of proportion with respect to QAlb.
- This indicates local production of immunoglobulins within the central nervous system, as occurs in multiple sclerosis, chronic CNS infections, etc.
🧪 What is it used for?
The Reiber Diagram is useful for:
- Diagnose or confirm diseases with intrathecal IgG synthesis (such as multiple sclerosis, neurosyphilis, tuberculous meningitis).
- Distinguish whether a hypergammaglobulinorrachia is due to intrathecal synthesis o to an alteration of the barrier.
- To evaluate whether an IgG alteration in the CSF has its origin systemic or neurological.
It can also be applied to the analysis of IgA e IgM, adjusting the corresponding diagram, which is useful in certain infectious or inflammatory diseases.
