Cerebrospinal fluid CD4 + /CD8 + ratio in diagnosing neurosarcoidosis

Objective 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. Materials and Methods 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. Results 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. Conclusion 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.