Development and validation of an automated latex-enhanced immunoassay for prealbumin

Abstract

The measurement of circulating prealbumin has been shown to be clinically useful in the assessment of nutritional status, both as an initial screen and in the monitoring of nutritional recovery. We describe a fully automated, noncompetitive, homogenous, light-scattering immunoassay that has been developed for this analyte on a Dimension® (Dade) analyzer. A sheep anti-prealbumin IgG fraction was covalently coupled to 40-nm chloromethyl styrene particles and, after the addition of sample, polyethylene glycol-assisted immunoagglutination was monitored by turbidimetry. The prealbumin working assay range was 8–550 mg/L at a sample volume of 2 μL and a reaction time of 6.5 min. When data were analyzed using ANOVA, total and within-run assay imprecision values (CVs) were 1–5%, and calibration and reagent stabilities were in excess of 40 days. Mean analytical recoveries were 102% ± 4% (SD), and there was no lack of parallelism. Hemolysis, lipemia, and bilirubin did not interfere. Both plasma anticoagulated with heparin or EDTA and serum from plain or serum-separation tubes were acceptable as sample matrices. Comparison with the Beckman Array® method gave a Passing and Bablok regression of: Dimension analyzer = 1.01Beckman + 7.1 (n = 103), using a common calibrator. We conclude that the prealbumin method is appropriate for clinical use according to the analytical criteria used in this study.

Prealbumin: The clinical utility and analytical methodologies

“…50 Both light-scattering methods demonstrated similar within-run and between-run imprecision, whereas radial immunodiffusion assay demonstrated higher between-run imprecision. 51 However, all three assays correlated well in measuring prealbumin. 50 Holownia et al.…”

“…proposed that the sensitivity of the light-scattering assay can be improved significantly by using particle-enhanced techniques in comparison to the conventional non-enhanced methods. 51 They have developed and evaluated a latex-particle-enhanced immune-turbidimetric assay in an automated platform (Dimension Clinical Chemistry analyser) with good precision and specificity. 51 Purified prealbumin (>96% purity) has been used as the calibration material (Scipac, Kent, UK; product code P171-1).…”

“…51 They have developed and evaluated a latex-particle-enhanced immune-turbidimetric assay in an automated platform (Dimension Clinical Chemistry analyser) with good precision and specificity. 51 Purified prealbumin (>96% purity) has been used as the calibration material (Scipac, Kent, UK; product code P171-1). 10 This newly developed method has been compared for prealbumin using both serum and heparin or EDTA anticoagulated plasma, with the selected reference method (Beckman Array system, Beckman Instruments) which has been calibrated against the International Federation of Clinical Chemistry (IFCC) reference material CRM 470.…”

Construction of a synthetic phage-displayed Nanobody library with CDR3 regions randomized by trinucleotide cassettes for diagnostic applications

“…Based on the biotin-SA interaction, the S-anti-PA Nb coupled with HRP was used as the detector and the I-anti-PA Nb48 conjugated with biotin was used as the capture protein to detect PA. A linear relation between the absorbance at 450 nm and the concentration of PA was observed in a range from 50 to 1000 ng/mL with a R 2 of 0.9592, and the LOD is 27.1 ng/mL. The relatively broad consensus reference range of PA for an adult is 120–500 mg/L [ 22 ]. Several studies [ 40 , 41 ] have recommended that a concentration of <110 mg/L is high risk, a chief nutritional therapy is necessary; 110–170 mg/L is considered moderate risk, requiring less serious nutritional therapy; and >170 mg/L is of little or no risk.…”

“…PA, a hepatic protein, is especially sensitive to early phases of reduced nutrition, particularly caloric intake and nitrogen balance [ 20 , 21 ], in addition, the concentration of PA rapidly returns to normal values within the reference interval, once the malnutrition has been corrected [ 21 ]. Therefore, the assay of circulating PA has revealed to be clinically valuable in the evaluation of nutritional status, both as an initial screen and in the monitoring of nutritional recovery [ 22 ]. NGAL belongs to the lipocalin superfamily, which is found in granules of neutrophils [ 23 , 24 ].…”