Effect of Variability of Plasma Interferences on the Accuracy of Drug Immunoassays

Abstract

Most immunoassays applied to drugs in human plasma do not use an extraction of analyte. To compensate for interferences due to plasma proteins or salts, standards are prepared in drug-free plasma. Because the concentration of plasma components varies from one subject to another, it is likely that the drug-free plasma is not representative of the potential interference in each plasma. Using two immunoassays, for a steroid (nomegestrol acetate) and a heptapeptide (BN 52080), the authors have shown that tracer binding to the antibody may vary significantly between plasma from different subjects. Intersubject variability of tracer-antibody binding was 21.6% (coefficient of variation for 25 subjects) for nomegestrol acetate. When the same plasma were spiked with the steroid at a concentration corresponding to the central part of the standard curve, the recovery was between 39 and 215%. Intersubject variability in tracer binding was lower (7.7%) for the peptide immunoassay, but still affected accuracy. The authors show that this problem is common to direct immunoassays for other drugs and must be solved in assay development.

Mass spectrometric quantification of AcSDKP‐NH2 in human plasma and urine and comparison with an immunoassay

“…It is known that the blank matrix used to construct standard curves in immunoassay may not reflect the variability in an individual matrix, which might lead to inaccuracy exceeding 30%. [16] A typical illustration appears from the comparative analysis of a fifth subject who was not included in the previous comparisons of EIA and LC/MS/MS. In this particular subject, AcSDPK-NH 2 immunoreactivity was detected by EIA before injection of the peptide, and the plasma concentrations measured by EIA during infusion were~10 times higher than those recorded for the other subjects ( Fig.…”

“…However, they may be plagued by poor specificity and interindividual matrix effects leading to reduced accuracy which may compromise the validation of candidate biomarkers for the diagnosis of disease states. [13][14][15][16] As an alternative to immunoassays, quantitative mass spectrometry (MS) has advantages in terms of robustness and specificity through the use of internal standards, adapted sample preparations and chromatographic separations. [13,[17][18][19] Mass spectrometry has already proved its applicability in the field of absolute quantitation of proteins and peptides in complex matrices such as plasma and urine, with sensitivity sometimes greater than that of enzyme immunoassay (EIA).…”

A Review of Therapeutic Drug Monitoring and Model-Informed Precision Dosing in Personalized Medicine

“…Bilirubin (171 µmol/L) có thể ảnh hưởng tới định lượng acetaminophen và vancomycin. Lipid máu tạo ra độ đục gây chênh lệch kết quả đo phổ và sắc kí, vì vậy cần bị loại bỏ thông qua li tâm siêu tốc; protein niệu có thể ảnh hưởng tới sự gắn của chất phân tích với kháng thể trong quy trình định lượng miễn dịch [16,24,25].…”

Gentamicin assay in human serum by solid-phase extraction and capillary electrophoresis

“…In this method absolute recovery was not reached, and the results indicated that differences of up to 32% between the reactivities of the antibodies to the gentamicin components existed [14]. Remarkable intersubject variability has been reported for immunoassays in general, and the accuracy of the results has been questioned, especially at low concentrations [15]. Isoherranen and Soback [12] developed a chromatographic method for reliable detection, identification, and quantification of three major gentamicin components in body fluids in the concentration range 0.1-20 mg/L.…”