title: Diagnostic utility of a modified forearm ischemic exercise test and technical issues relevant to exercise testing.
abstract: The sensitivity and specificity of a modified forearm ischemic test (FIT) are described in the diagnosis of glycogen storage disease, myoadenylate deaminase deficiency, and mitochondrial disease. FIT and muscle biopsy results were reviewed from 99 patients (glycogen storage disease [GSD], myoadenylate deaminase deficiency [AMPD], mitochondrial disease [MITO], miscellaneous neuromuscular disorders, and controls). The influence of catheter placement and an antecedent sugar bolus were also assessed in healthy young men. The FIT had a sensitivity of 1.00 and a specificity of 1.00 for a diagnosis of GSD, whereas the corresponding values were 1.00 and 0.37 for AMPD deficiency. A baseline lactate of >2.5 mmol/L provided the highest sensitivity (0.62) and specificity (1.00) for MITO disease. A baseline and +1 min sample provided optimal sensitivity and specificity for GSD and AMPD deficiency. Catheter placement in any vein other than the ipsilateral antecubital resulted in attenuated lactate responses (P < 0.0001). A pre-FIT sugar bolus did not alter the postexercise lactate or ammonia response. Thus, a modified FIT was helpful in the diagnosis of GSD and excluding AMPD deficiency, but not in the diagnosis of MITO disease. Catheter placement is critical to the interpretation of a FIT, whereas pretesting diet is less important.
authors.affiliation: Department of Neurology, McMaster University Medical Center, Room 4U4, 1200 Main Street W, Hamilton, Ontario L8N 3Z5, Canada. tarnopol@mcmaster.ca
authors.forename: Mark
authors.initials: M
authors.lastname: Tarnopolsky
authors.forename: Leslie
authors.initials: L
authors.lastname: Stevens
authors.forename: Jay R
authors.initials: JR
authors.lastname: MacDonald
authors.forename: Christine
authors.initials: C
authors.lastname: Rodriguez
authors.forename: Douglas
authors.initials: D
authors.lastname: Mahoney
authors.forename: Jim
authors.initials: J
authors.lastname: Rush
authors.forename: John
authors.initials: J
authors.lastname: Maguire
mesh_terms: D000328:Adult; D000641:Ammonia / Q000097:blood; D002406:Catheterization, Peripheral; D004435:Eating; D005080:Exercise Test; D005542:Forearm / Q000098:blood supply; D006008:Glycogen Storage Disease / Q000175:diagnosis* / Q000503:physiopathology*; D006801:Humans; D007511:Ischemia / Q000175:diagnosis* / Q000503:physiopathology*; D019344:Lactic Acid / Q000097:blood; D008297:Male; D028361:Mitochondrial Diseases / Q000175:diagnosis / Q000503:physiopathology; D009468:Neuromuscular Diseases / Q000175:diagnosis / Q000503:physiopathology; D012680:Sensitivity and Specificity
chemical_list: D019344:Lactic Acid; D000641:Ammonia