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Falsely raised plasma theophylline concentrations in renal failure
1Department of Pathology, University of Ottawa, School of Medicine, Ontario, Canada.
European Journal of Clinical Pharmacology
|January 1, 1988
Summary
Plasma theophylline measurements in patients with renal failure require careful interpretation. Four different assay methods showed significant variability, particularly the dipstick immunoassay, impacting clinical decisions.
Area of Science:
- Clinical Chemistry
- Pharmacokinetics
- Renal Medicine
Background:
- Theophylline is a critical medication for respiratory conditions.
- Accurate plasma theophylline levels are essential for therapeutic drug monitoring.
- Renal impairment can alter theophylline pharmacokinetics, potentially affecting drug levels.
Observation:
- This study evaluated four analytical methods for plasma theophylline quantification in patients with renal impairment.
- Methods included high-performance liquid chromatography (HPLC), fluorescence polarization immunoassay (FPIA), enzyme immunoassay (EIA), and dipstick immunoassay (DI).
- Eighteen patients with renal impairment undergoing theophylline therapy were included.
Findings:
- Plasma theophylline levels varied significantly across the four methods.
- HPLC, FPIA, and EIA yielded comparable results (mean 63.4-70 mumol/l).
- The dipstick immunoassay (DI) showed substantially higher values (mean 122 mumol/l).
- A strong correlation (r=0.94, p<0.01) was observed between serum creatinine levels and the discrepancy between HPLC and DI results.
Implications:
- The dipstick immunoassay may overestimate theophylline concentrations in patients with renal failure.
- Clinicians must exercise caution when interpreting plasma theophylline results in renally impaired patients.
- Assay method selection is critical for accurate therapeutic drug monitoring in this population.