Abstract
The total analytical error of a photonic crystal (PC) biosensor in the determination of ferritin and soluble transferrin receptor (sTfR) as biomarkers of iron deficiency anemia in chronic kidney disease (CKD) patients was evaluated against certified ELISAs. Antigens were extracted from sera of CKD patients using functionalized iron-oxide nanoparticles (fAb-IONs) followed by magnetic separation. Immuno-complexes were recognized by complementary detection Ab affixed to the PC biosensor surface, and their signals were followed using the BIND instrument. Quantification was conducted against actual protein standards. Total calculated error (TEcalc) was estimated based on systematic (SE) and random error (RE) and compared against total allowed error (TEa) based on established quality specifications. Both detection platforms showed adequate linearity, specificity, and sensitivity for biomarkers. Means, SD, and CV were similar between biomarkers for both detection platforms. Compared to ELISA, inherent imprecision was higher on the PC biosensor for ferritin, but not for sTfR. High SE or RE in the PC biosensor when measuring either biomarker resulted in TEcalc higher than the TEa. This did not influence the diagnostic ability of the PC biosensor to discriminate CKD patients with low iron stores. The performance of the PC biosensor is similar to certified ELISAs; however, optimization is required to reduce TEcalc.
Highlights
Anemia is suspected in all chronic kidney disease (CKD) patients who are undergoing hemodialysis [1]
For soluble transferrin receptor (sTfR), the TEa has been estimated as a percentage of a clinically relevant concentration, and for ferritin as data agreed upon average
Was 9.8%, which is lower than the TEa at the clinical cutoff of 5.3 μg/mL. This demonstrated that the performance of the photonic crystal (PC) compared to enzyme-linked immunosorbent assay (ELISA) resulted in less error than would be observed in biological variation within and between individuals
Summary
Anemia is suspected in all chronic kidney disease (CKD) patients who are undergoing hemodialysis [1]. Ferritin is a large spherical protein that stores iron atoms within a cage-like structure [11], while TSAT is a non-protein biomarker that reflects the iron available for erythropoiesis These biomarkers do not always deliver dependable results when working with CKD patients undergoing hemodialysis due to its inflammatory nature [10]. As POC biosensors become available for clinical diagnostic applications, method validation studies are required to estimate their total analytical error. This variation helped reduce interference signals caused by non-specific binding of proteins in a serum matrix—a common problem shared by all diagnostic platforms This variation of the PC biosensor protocol might be useful to evaluate sera from CKD patients known to contain high levels of interference molecules due to the inability of the kidneys to effectively excrete endogenous [31,32] and exogenous compounds [33]. The total analytical error of the PC biosensor in quantifying IDA biomarkers was determined using FDA-certified ELISAs as the reference methods
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