TY - JOUR
T1 - Phenylalanine loading as a diagnostic test for DRD
T2 - Interpreting the utility of the test
AU - Saunders-Pullman, R.
AU - Blau, N.
AU - Hyland, K.
AU - Zschocke, J.
AU - Nygaard, T.
AU - Raymond, D.
AU - Shanker, V.
AU - Mohrmann, K.
AU - Arnold, L.
AU - Tabbal, S.
AU - Deleon, D.
AU - Ford, B.
AU - Brin, M.
AU - Chouinard, S.
AU - Ozelius, L.
AU - Klein, C.
AU - Bressman, S. B.
N1 - Funding Information:
The authors thank the families who have graciously participated in this study. This study was supported in part by the Dystonia Medical Research Foundation (RSP, SBB), the Nell and Herbert Singer Fund (RSP), by the Swiss National Science Foundation, Grant No. 31-66953.01 (NB), by the Medical University of Luebeck, Grant No. J-15 (CK), and the Fritz Thyssen Stiftung (CK).
PY - 2004/11
Y1 - 2004/11
N2 - Phenylalanine loading has been proposed as a diagnostic test for autosomal dominant DRD (dopa-responsive dystonia), and recently, a phenylalanine/tyrosine (phe/tyr) ratio of 7.5 after 4 h was reported as diagnostic of DRD. To test the utility of this test in another sample with DRD, we administered an oral challenge of phenylalanine (100 mg/kg) to 11 individuals with DRD and one non-manifesting gene carrier. Only 6/12 had a 4 h phe/tyr ratio of greater than 7.5, suggesting that additional parameters must be set to avoid missing the diagnosis of DRD, including the need for the plasma phenylalanine to reach a minimum level 600 in order for the test to be valid. We propose that in cases where this minimum plasma phenylalanine level is not reached, plasma tetrahydrobiopterin should be measured or alternatively other symptomatic family members should be screened.
AB - Phenylalanine loading has been proposed as a diagnostic test for autosomal dominant DRD (dopa-responsive dystonia), and recently, a phenylalanine/tyrosine (phe/tyr) ratio of 7.5 after 4 h was reported as diagnostic of DRD. To test the utility of this test in another sample with DRD, we administered an oral challenge of phenylalanine (100 mg/kg) to 11 individuals with DRD and one non-manifesting gene carrier. Only 6/12 had a 4 h phe/tyr ratio of greater than 7.5, suggesting that additional parameters must be set to avoid missing the diagnosis of DRD, including the need for the plasma phenylalanine to reach a minimum level 600 in order for the test to be valid. We propose that in cases where this minimum plasma phenylalanine level is not reached, plasma tetrahydrobiopterin should be measured or alternatively other symptomatic family members should be screened.
KW - Dopa-responsive-dystonia
KW - Dystonia diagnosis
KW - GTPCH-1 mutations
KW - Phenylalanine loading
UR - http://www.scopus.com/inward/record.url?scp=8144220153&partnerID=8YFLogxK
U2 - 10.1016/j.ymgme.2004.07.010
DO - 10.1016/j.ymgme.2004.07.010
M3 - Article
C2 - 15542391
AN - SCOPUS:8144220153
SN - 1096-7192
VL - 83
SP - 207
EP - 212
JO - Molecular Genetics and Metabolism
JF - Molecular Genetics and Metabolism
IS - 3
ER -