title: Cerebrospinal fluid analysis in the workup of GLUT1 deficiency syndrome: a systematic review.
abstract: OBJECTIVE
  GLUT1 deficiency syndrome is a treatable neurometabolic disorder, characterized by a low concentration of glucose in cerebrospinal fluid (CSF) and a decreased CSF to blood glucose ratio. Reports of patients with apparently normal CSF glucose levels, however, have raised the question whether CSF analysis is a reliable screening tool for GLUT1 deficiency syndrome.
  
  
  OBJECTIVE
  To determine the value of CSF analysis in the workup of GLUT1 deficiency syndrome.
  
  
  METHODS
  PubMed was searched until July 2012 by using the terms glucose transporter 1 (GLUT-1) deficiency syndrome, glucose transporter defect, and SLC2A1-gene. Relevant references mentioned in the articles were also included. The CSF results of all patients with genetically proven GLUT1 deficiency syndrome described in literature were reevaluated.
  
  
  RESULTS
  The levels of glucose in CSF, the CSF to blood glucose ratios, and the levels of lactate in CSF were reported for 147 (94%), 152 (97%), and 73 (46%) of 157 patients, respectively. The CSF glucose levels ranged from 16.2 to 50.5 mg/dL and were at or below the 10th percentile for all 147 patients. The CSF to blood glucose ratios ranged from 0.19 to 0.59 and were at or below the 10th percentile for 139 of 152 patients (91%), but they could be within the normal range as well. The CSF lactate levels ranged from 5.4 to 13.5 mg/dL and were at or below the 10th percentile for 59 of 73 patients (81%). A typical CSF profile for GLUT1 deficiency syndrome, which is defined as a CSF glucose level at or below the 10th percentile, a CSF to blood glucose ratio at or below the 25th percentile, and a CSF lactate level at or below the 10th percentile, was found in only 35 of 4099 CSF samples (0.9%) present in our CSF database of patients who received a diagnosis other than GLUT1 deficiency syndrome.
  
  
  CONCLUSIONS
  We conclude that if age-specific reference values are applied, CSF glucose and lactate levels are adequate biomarkers in the diagnostic workup of GLUT1 deficiency syndrome. Future availability of whole-exome sequencing in clinical practice will make the existence of a reliable biomarker for GLUT1 deficiency syndrome even more important, in order to interpret genetic results and, even more importantly, not to miss SLC2A1-negative patients with GLUT1 deficiency syndrome.
authors.affiliation: Department of Neurology, Radboud University Medical Centre, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, the Netherlands.
authors.forename: Wilhelmina G
authors.initials: WG
authors.lastname: Leen
authors.forename: Ron A
authors.initials: RA
authors.lastname: Wevers
authors.forename: Erik-Jan
authors.initials: EJ
authors.lastname: Kamsteeg
authors.forename: Hans
authors.initials: H
authors.lastname: Scheffer
authors.forename: Marcel M
authors.initials: MM
authors.lastname: Verbeek
authors.forename: Michèl A
authors.initials: MA
authors.lastname: Willemsen
mesh_terms: D000367:Age Factors; D001786:Blood Glucose; D002239:Carbohydrate Metabolism, Inborn Errors / Q000097:blood / Q000134:cerebrospinal fluid*; D005947:Glucose / Q000134:cerebrospinal fluid*; D006801:Humans; D009004:Monosaccharide Transport Proteins / Q000097:blood / Q000134:cerebrospinal fluid / Q000172:deficiency*; D039781:PubMed / Q000706:statistics & numerical data
chemical_list: D001786:Blood Glucose; D009004:Monosaccharide Transport Proteins; D005947:Glucose