Instability of standard calibrators may be involved in overestimating vancomycin concentrations determined by fluorescence polarization immunoassay

Hiroko Morishige, Hideki Shuto, Ichiro Ieiri, Kenji Otsubo, Ryozo Oishi

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)

Abstract

Fluorescence polarization immunoassay (FPIA) is widely used to determine serum vancomycin concentrations, and it has been shown to overestimate vancomycin concentrations in sera from renally impaired patients. This phenomenon has generally been thought to result from interference by vancomycin crystalline degradation products (CDP-1). In this study, we confirmed that serum vancomycin concentrations in various patients determined by FPIA were higher than those determined by high-performance liquid chromatography (HPLC) or enzyme multiplied immunoassay (EMIT). However, the quantitative differences in the serum vancomycin concentrations determined by FPIA versus HPLC were higher than the CDP-1 concentrations, even when the cross-reactivity of FPIA to CDP-1 is assumed to be 100%. When the vancomycin calibrators for FPIA were stored at 4°C for 30 days, their concentrations determined by FPIA and HPLC decreased by 14 and 20%, respectively, and CDP-1 corresponding to 20% of primary vancomycin was formed. When stored at 25°C, the degradation of vancomycin was more marked. We concluded that not only the cross-reactivity of FPIA to CDP-1 but also the instability of calibrators may cause the overestimation of serum vancomycin concentrations determined by FPIA.

Original languageEnglish
Pages (from-to)80-85
Number of pages6
JournalTherapeutic drug monitoring
Volume18
Issue number1
DOIs
Publication statusPublished - Feb 6 1996

All Science Journal Classification (ASJC) codes

  • Pharmacology
  • Pharmacology (medical)

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