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Plasma creatinine assessment in creatine deficiency: A diagnostic pitfall
N M Verhoeven1, W S Guérand, E A Struys
1Department of Clinical Chemistry, University Hospital Vrije Universiteit, Amsterdlam, The Netherlands. verhoeven@azvu.nl
Journal of Inherited Metabolic Disease
|February 24, 2001
Summary
Guanidinoacetate methyltransferase (GAMT) deficiency causes low plasma creatinine. The common Jaffé method may falsely show normal creatinine levels in affected patients, hindering diagnosis.
Area of Science:
- Biochemistry
- Genetics
- Metabolic Disorders
Background:
- Guanidinoacetate methyltransferase (GAMT) deficiency is an inborn error of creatine biosynthesis.
- Patients exhibit elevated guanidinoacetate and decreased creatinine levels in biological fluids.
- Accurate plasma creatinine quantification is crucial for diagnosing GAMT deficiency.
Purpose of the Study:
- To evaluate different quantification techniques for plasma creatinine in GAMT deficiency.
- To assess the reliability of the Jaffé method for detecting decreased creatinine in GAMT deficiency.
Main Methods:
- Comparison of creatinine measurements in plasma from GAMT-deficient patients using the Jaffé method, enzymatic methods, and HPLC.
- Analysis of potential interference in creatinine measurements.
Main Results:
- Plasma creatinine in GAMT-deficient patients appeared normal with the Jaffé method but decreased with enzymatic and HPLC methods.
- The Jaffé method's inaccuracy was not due to guanidinoacetate interference.
- Urine creatinine measurements by Jaffé and enzymatic methods showed similar results, indicating reliability in urine analysis.
Conclusions:
- The widely used Jaffé method is unreliable for measuring plasma creatinine in GAMT deficiency.
- Routine plasma creatinine measurements using the Jaffé method may fail to exclude GAMT deficiency.
- Enzymatic or HPLC methods are recommended for accurate plasma creatinine quantification in suspected GAMT deficiency cases.