Abstract
The measurement of serum netilmicin (NTL) by substrate labeled fluoroimmunoassay (SLFIA) was evaluated with the purpose to apply to the clinical pharmacokinetic dosing regimen service. Three serum dilution methods including 51-, 16-, and 6-fold dilution factors were used for the measurement based on the method recommended by the manufacture of the assay apparatus and slightly modified by the authors. The maximum within-assay variance (CVw%), between-assay variance (CVb%) and the range of analytical recovery (%) measured by 51-fold dilution method were 4.2%, 11.9% and 102-104%(minimum-maximum values) respectively in NTL concentration ranging from 2 to 10 mcg/ml, but low precision (14.7%), very low reproducibility (30. 2%) and large negative bias (68.5%) were observed in 1 mcg/ml. CVw%, CVb% and the range of recovery (%) by 16-fold dilution method were 6.5%, 12.6% and 104.1-115.6% respectively in NTL concentration ranging from 0.7 to 2mcg/ml, but very low reproducibility (29.3%) was observed in 0.3 mcg/ml. CVw%, CVb% and the range of recovery (%) by 6-fold dilution method were 3.2%, 12.2% and 100.6-119.3% respectively in NTL concentration ranging from 0.3 to 1 mcg/ml. It may be a rational and practical idea with the purpose to apply to NTL dosing regimen that SLFIA-NTL assay of serum NTL concentration should be concomitantly used by 51-fold and 16-fold dilution method. This combination procedure may give accuracy through value and patient pharmacokinetic parameters, therefore, a safe and effective manner of dosing of NTL can be decided.
