How long can xanthochromia be used to rule out Subarachnoid Hemorrhage (SAH)?

From the Guidelines

Xanthochromia can be used to rule out subarachnoid hemorrhage (SAH) for up to 2 weeks after symptom onset, though it is most reliable when tested between 12 hours and 7 days after the initial headache. The test should not be used before 12 hours as xanthochromia may not have developed yet, potentially leading to false negatives 1. Xanthochromia refers to the yellowish discoloration of cerebrospinal fluid (CSF) that occurs when red blood cells break down and release bilirubin following a SAH. This discoloration is a more specific indicator of true SAH than the presence of red blood cells in CSF, which can occur due to a traumatic lumbar puncture.

Key Considerations

• Spectrophotometry is the preferred method for detecting xanthochromia as it is more sensitive than visual inspection.
• The persistence of xanthochromia for up to two weeks makes it valuable for diagnosing SAH in patients who present days after their initial symptoms, when CT scans may have become negative.
• According to the 2023 guideline for the management of patients with aneurysmal subarachnoid hemorrhage, LP for xanthochromia evaluation should be performed in patients presenting > 6 hours from ictus in whom there is high suspicion for SAH 1.

Diagnostic Approach

• High-quality CT scanners can detect SAH with a high sensitivity, especially when the images are interpreted by fellowship-trained, board-certified neuroradiologists.
• For patients presenting within 6 hours of headache onset who have no new neurological deficits, the lack of SAH on a noncontrast head CT is likely sufficient to exclude aSAH 1.
• The Ottawa SAH Rule serves as a method to screen out individuals with a low likelihood of aSAH, and application of the rule requires that patients who present with a severe headache and meet any of the criteria outlined may need to undergo additional testing, as directed by the treating physician 1.

From the Research

Xanthochromia in Diagnosing Subarachnoid Hemorrhage (SAH)

• Xanthochromia is a test used to diagnose SAH by detecting the presence of bilirubin in the cerebrospinal fluid (CSF) 2, 3, 4, 5.
• The sensitivity and specificity of xanthochromia in diagnosing SAH vary depending on the method used, with spectrophotometry being more sensitive and specific than visual inspection 2, 3, 4, 5.

Time Frame for Xanthochromia to Rule Out SAH

• Xanthochromia can be used to rule out SAH if the CSF is obtained between 12 hours and 2 weeks from the time of headache onset 3.
• For patients with a negative computed tomography (CT) within six hours of symptom onset, spectrophotometry for xanthochromia in the CSF had a diagnostic sensitivity of 100% and a diagnostic specificity of 98.5% 2.
• Incorporating red cell count (RCC) with xanthochromia can improve diagnostic accuracy by reducing false positive tests and inconclusive tests 5.

Limitations of Xanthochromia

• Visual inspection of CSF for xanthochromia lacks the sensitivity necessary to reliably exclude the diagnosis of SAH, with a sensitivity of 47.3% 3.
• Spectrophotometric definitions of xanthochromia have only moderate to low specificity for SAH, which could lead to increased angiography rates and unnecessary complications 4.
• The positive yield of xanthochromia is low, but it can identify a small percentage of SAH cases, highlighting the importance of using it in conjunction with other diagnostic methods 5.