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Urinary creatinine instability falsely increases the deoxypyridinoline/creatinine quotient
Ulrich Schneider1, Edward A Schober, Nikolaus A Streich
1Orthopädische Universitätklinik, Klinikum der RWTH Aachen, Pauwelsstr 30, 52074 Aachen, Germany. U.Schneider@post.rwth-aachen.de
Clinica Chimica Acta; International Journal of Clinical Chemistry
|September 3, 2002
Summary
Urinary deoxypyridinoline crosslinks (Dpd) normalized by creatinine are a bone resorption marker. Storing urine samples at -20°C for over 14 days is recommended to prevent falsely elevated Dpd/creatinine ratios due to creatinine degradation.
Area of Science:
- Biochemistry
- Orthopedics
- Clinical Chemistry
Background:
- Urinary deoxypyridinoline crosslinks (Dpd) normalized by creatinine serve as a key biochemical marker for pathological bone resorption.
- Assessing Dpd/creatinine stability under various storage conditions is crucial for accurate clinical interpretation.
Purpose of the Study:
- To investigate the impact of different storage conditions on the stability of the Dpd/creatinine ratio in urine.
- To determine optimal storage protocols for preserving the integrity of this bone resorption biomarker.
Main Methods:
- Urine samples from 14 healthy individuals (control) and 14 patients with aseptic endoprosthetic loosening (AEL) were analyzed.
- The Dpd/creatinine ratio was measured in fresh samples and after storage under various conditions, including -20°C.
Main Results:
- Storage at -20°C for 1 day significantly increased Dpd/creatinine in controls due to creatinine degradation.
- While less pronounced in AEL patients, increases in Dpd/creatinine were observed, primarily driven by decreased urinary creatinine concentration over time.
- Urinary creatinine concentration decreased to a plateau (75-80% of original) after approximately 10 days of storage.
Conclusions:
- Falsely elevated Dpd/creatinine quotients can occur due to sample storage.
- To ensure accurate measurement of bone resorption markers, urine samples should be analyzed fresh or stored consistently at -20°C or -80°C for at least 14 days.