Cerebrospinal fluid CD4⁺ /CD8⁺ ratio in diagnosing neurosarcoidosis

Neurosarcoidosis affects 5%-10% of patients with sarcoidosis. CD4⁺ /CD8⁺ ratio in bronchoalveolar lavage is included in diagnostic routine for pulmonary sarcoidosis. Previously, it has been suggested that a cerebrospinal fluid CD4⁺ /CD8⁺ ratio ≥5 can be an aid in diagnosing neurosarcoidosis.

This study included 66 cases where neurosarcoidosis was a differential diagnosis and hence subjected to the analysis of CSF CD4⁺ /CD8⁺ ratio by flow cytometry.

Eleven cases of neurosarcoidosis, had a significantly higher median CSF CD4⁺ /CD8⁺ ratio than the other group, P = .024. The median CSF CD4⁺ /CD8⁺ ratio was 4.2, hence not reaching the suggested level of ≥5 for diagnosing neurosarcoidosis. When combined, the elevated CSF CD4⁺ /CD8⁺ ratio ≥5 and an elevated CSF lymphocyte count (>3 lymphocytes/uL) gave a positive predictive value of 57% and a high negative predictive value of 88%, with a specificity of 95% for neurosarcoidosis.

The study confirms that increased CSF CD4⁺ /CD8⁺ ratio is associated with neurosarcoidosis but cannot alone distinguish the conditions from other neurological diagnoses. However, a ratio below <5 combined with an absence of pleocytosis in CSF yields a negative predictive value (NPV) of 88% suggesting a role for the analysis in differential diagnosing neuroinflammatory conditions.