HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Submit an electronic Letter to the Editor about this paper Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (12) Citing Articles via Google Scholar Google Scholar Articles by Arranz, J. A. Articles by Burlina, A. Search for Related Content PubMed PubMed Citation Articles by Arranz, J. A. Articles by Burlina, A. Related Collections Molecular Diagnostics and Genetics Pediatric Clinical Chemistry Evidence Based Laboratory Medicine and Test Utilization Endocrinology and Metabolism

Optimization of Allopurinol Challenge: Sample Purification, Protein Intake Control, and the Use of Orotidine Response as a Discriminative Variable Improve Performance of the Test for Diagnosing Ornithine Carbamoyltransferase Deficiency

¹ Unitat de Metabolopaties, Hospital Materno-Infantil Vall d'Hebron, 08035 Barcelona, Spain.

² Institut de Bioquímica Clínica, C/Mejia Lequerica s/n, Edifici Helios III, Planta Baixa, Corporació Sanitària, 08028 Barcelona, Spain.

³ Instituto de Biomedicina de Valencia (CSIC), C/Jaume Roig 11, 46010 Valencia, Spain.

⁴ Dipartimento di Pediatria, Università di Padova, Via Giustiniani 3, 35128 Padua, Italy.
^a Address correspondence to this author at: Laboratori de Metabolopaties, Hospital Materno-Infantil Vall d'Hebron, Ps. Vall d'Hebron 119-129, 08035 Barcelona, Spain. Fax 34 93 2746837; e-mail msentis.hmi{at}cs.vhebron.es

Background: The diagnosis of heterozygosity for X-linked ornithine carbamoyltransferase (OCT) deficiency has usually been based on measurement of the increase of orotate and orotidine excretion after an allopurinol load. We examined the choices of analyte, cutoff, and test conditions to obtain maximal test accuracy.

Methods: Urine orotate/orotidine responses to allopurinol load in 37 children (13 OCT-deficient and 24 non-OCT-deficient) and 24 women (7 at risk for carrier status and 17 not related to OCT-deficient children) were analyzed by liquid chromatography after sample purification by anion-exchange chromatography. Diagnostic accuracy was evaluated by nonparametric ROC curves.

Results: Sample purification was necessary to prevent interferences. Orotate and orotidine excretion increased with increased protein intake during the test. At a cutoff of 8 mmol orotidine/mol creatinine, sensitivity was 1.0 and specificity was 0.92 in mild forms of OCT deficiency. Results in monoplex carrier women may differ greatly from those expected because of the genetics of this deficiency.

Conclusions: Standardization of protein intake is required in the allopurinol loading test. A negative response in the face of clinical suspicion should be followed with a repeat test during a protein intake not <2.5 g · kg^-1 · day^-1. Measurements of orotidine provide better clinical sensitivity than measurements of orotate.© 1999 American Association for Clinical Chemistry

The following articles in journals at HighWire Press have cited this article:

				E. Riudor, J. A. Arranz, M. Rodes, F. Scaglia, Q. Zheng, W. E. O'Brien, J. Henry, J. Rosenberger, B. Lee, and P. Reeds Partial Ornithine Transcarbamylase Deficiency Pediatrics, May 1, 2003; 111(5): 1123 - 1124. [Full Text] [PDF]