EVALUATION OF THE UNITED KINGDOM NATIONAL EXTERNAL QUALITY ASSESSMENT SERVICE 2008 (UK NEQAS 2008) GUIDELINES FOR THE DIAGNOSIS OF SUBARACHNOID HEMORRHAGE USING SPECTROPHOTOMETRIC XANTHOCHROMIA: A RETROSPECTIVE STUDY

Abstract

Objective: Evaluation of the UK NEQAS 2008 guidelines for the interpretation of spectrophotometric xanthochromia. Method: A search of the laboratory database for all the xanthochromia test results between May 1st 2008 and May 1st 2009 was performed. Medical charts were reviewed for patients of Hôpital de l’Enfant-Jésus (HEJ) that had at least one detectable pigment (bilirubin, oxyhemoglobin, or methemoglobin). Xanthochromia results obtained with 4 different criteria (Chalmers original, Modified Chalmers, Duiser and UK NEQAS 2008) were compared. Results: We reviewed 41 medical charts (2 patients with duplicate lumbar punctures (LP) for a total of 43 LP). For these 41 patients there were 11 positive xanthochromia results, 5 of which were in concordance with a final diagnosis of subarachnoid hemorrhage (SAH). The diagnosis of the 6 other positive xanthochromia results were as follow: meningeal spread of a lymphoma, cerebral amyloid angiopathy, exertional headache, viral encephalitis with a possibility of petechiaes on the cerebral CT and second LP. Interpretation (negative/positive) of 40/43 LP was identical for the 4 methods. 2 LP were positive with Duiser and UK NEQAS 2008 but negative with Chalmers approaches (final diagnosis: SAH and cerebral amyloid angiopathy). 1 LP was positive only by the Duiser method (viral encephalitis). Conclusions: UK NEQAS 2008 guidelines identified all SAH but are sensitive to traumatic and pathologic meningeal lesions. Except for a case of viral encephalitis with a suspicion of cerebral petechiaes on CT, UK NEQAS 2008 gave xanthochromia results similar to the one in use at HEJ (Duiser). Chalmers original and Modified Chalmers methods missed one of the five SAH.