Medical Laboratory Scientist ASCP Practice Exam 2025 – Complete Study Guide

The IgG index is a diagnostic tool used to assess the production of immunoglobulin G (IgG) within the central nervous system (CNS). When there is an increase in IgG levels in cerebrospinal fluid (CSF), the IgG index helps to differentiate whether this increase is due to normal production within the CNS or if it results from a pathological process such as contamination from blood (indicative of a blood-brain barrier breach).

Increased production of IgG within the CNS suggests an inflammatory or immune response occurring within the central nervous system, which may be associated with various neurological disorders such as multiple sclerosis, infections, or other inflammatory conditions. By establishing the IgG index, one can distinguish between an increase due to local synthesis in the CNS versus an elevation that might be due to contamination from peripheral blood, thus providing valuable insights into the underlying pathology.

The other options, while related to the evaluation of IgG in CSF, do not encompass the dual possibilities of increased production in the CNS or contamination as effectively as the correct choice. Observing both aspects is crucial for accurate diagnosis and understanding the immunological activity within the CNS.