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 11 cases of neurosarcoidosis, had a significantly higher median CSF CD4+/CD8+ ratio than the other group, p=0.024. 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.