An elevated peripheral neutrophil-lymphocyte ratio is an indicator of inflammation. Investigators from a Turkish university hospital hypothesized that this ratio might differ in patients with subarachnoid hemorrhage (SAH) versus those with other headache syndromes. They performed a retrospective study of emergency department patients with headaches.
The retrospective study included 121 patients with SAH, 123 with migraine (only migraineurs with neurology clinic follow-up were included), and 987 with other primary headache syndromes. Median neutrophil-lymphocyte ratio was significantly higher in SAH patients than in the migraine or other headache patients, At a neutrophil-lymphocyte ratio cutoff of 4.0, the sensitivity was 86% and specificity was 97%.
This is only one retrospective study and the results must be replicated in a prospective study, but the results are interesting and can provide another piece of supportive data in patients presenting to the ED with a severe headache. With modern CT scanning, SAH can be ruled out with 100% certainty if a negative CT scan is obtained within 6 hours of headache onset. The utility of a low serum neutrophil-lymphocyte ratio is to reassure clinicians after a negative head CT in patients with a suspicious headache for more than 6 hours. Also, if well validated, this test may be able to supplant the need for a head CT in some cases.