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Published on: May 10, 2013
Plasma creatinine results derived from an endpoint modification of the Jaffé method
S J Schurman1, S A Perlman, W Chamizo
1Department of Pediatrics, University of South Florida College of Medicine and All Children's Hospital, St Petersburg 33701, USA.
Insights
The Olympus AU5000 endpoint method for plasma creatinine (PCr) overestimates results in children compared to kinetic methods. This can complicate PCr interpretation, especially in younger pediatric patients.
Area of Science:
- Clinical Chemistry
- Pediatric Nephrology
- Laboratory Medicine
Background:
- Plasma creatinine (PCr) measurement is crucial for assessing kidney function in children.
- The Jaffé method is a common technique for PCr analysis, with variations in endpoint and kinetic approaches.
- Discrepancies between different PCr assay methods can impact clinical interpretation.
Purpose of the Study:
- To evaluate the Olympus AU5000 endpoint PCr method against a kinetic Jaffé technique.
- To assess the clinical implications of PCr measurement differences in pediatric populations.
Main Methods:
- Paired plasma samples were analyzed using the Olympus AU5000 endpoint method and a kinetic Jaffé method.
- Results were compared, focusing on PCr values within the normal pediatric range.
Main Results:
- The Olympus AU5000 endpoint method yielded significantly higher PCr results than the kinetic method (P<0.0001).
- Higher PCr values (0.1-0.3 mg/dl) were observed in 100% of samples analyzed by the endpoint method.
- The discrepancy was particularly notable when compared against established pediatric age- and sex-adjusted normal ranges.
Conclusions:
- The Olympus AU5000 endpoint method may lead to overestimation of plasma creatinine in pediatric patients.
- Difficulty in interpreting results arises from method-specific biases and non-specific reference ranges.
- Laboratories must provide comprehensive, age- and sex-adjusted normal PCr ranges for accurate clinical decision-making.
Abstract:
For values in the normal pediatric range, endpoint modifications of the Jaffé method for measuring plasma creatinine (PCr) yield higher results than other commonly used techniques. In an effort to evaluate the Olympus AU5000 endpoint method used by the large reference laboratory to which many of our patients are directed by their third-party payor, we compared results with a kinetic Jaffé technique using paired samples from the same specimens. In 46 samples, the kinetic method measured Pcr at < or =0.8 mg/dl, whereas the endpoint technique PCr was higher by 0.1 mg/dl in 6 (13%), 0.2 mg/dl in 23 (50%), and 0.3 mg/dl in 16 (35%) samples (P<0.0001). The combination of these higher values and the same reported normal range for all children ages 2-12 years (0.3-1.0 mg/dl) and 13-17 years (0.7-1.4 mg/dl) makes interpretation of Olympus AU5000 endpoint method results difficult, particularly for younger children. The results reinforce the need for each laboratory to provide comprehensive age- and sex-adjusted normal PCr ranges.
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