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Accuracy of serum ferritin determinations in tissue preparations and human serum
J D van Suijlen1, P C van Noord, B Leijnse
1Academic Hospital Dijkzigt Rotterdam, Department of Clinical Chemistry (CKCL), The Netherlands.
Insights
Standardizing ferritin immunoassays is crucial. While a reference preparation reduced variability, current kits lack accuracy due to method and antibody differences, underestimating total ferritin levels.
Area of Science:
- Clinical Chemistry
- Immunology
- Biotechnology
Background:
- Immunoassays for ferritin are widely used but suffer from inter-assay variability.
- The introduction of the NBSB 80/602 reference preparation was a step towards standardization.
- Significant discrepancies persist, hindering accurate comparison of ferritin assay results.
Purpose of the Study:
- To evaluate the effectiveness of the NBSB 80/602 reference preparation in standardizing ferritin immunoassays.
- To identify reasons for persistent inter-assay variability and inaccuracy.
- To propose requirements for an accurate reference method for serum ferritin determination.
Main Methods:
- Comparative analysis of different ferritin immunoassay kits.
- Investigation of antibody and antigen specificities.
- Assessment of interfering substances and isoferritin detection.
Main Results:
- The NBSB 80/602 preparation reduced inter-assay variability but did not enable result comparison.
- Assay methodology, antibody/antigen specificity, and interfering substances contribute to discrepancies.
- Current kits primarily detect basic isoferritins, underestimating acidic and intermediate forms.
- Immunological differences exist between standards and serum ferritin, indicating poor accuracy.
Conclusions:
- Accurate standardization of ferritin immunoassays requires addressing methodological and immunological differences.
- A comprehensive reference method is needed to detect all isoferritin forms (acidic, intermediate, basic).
- Such a method, combined with a reference preparation, is essential for accurate serum ferritin measurement and evaluation of routine methods.
Abstract:
Introduction of the NBSB 80/602 reference preparation for the calibration of ferritin immunoassays has reduced the inter-assay variability, and represents the first important step towards standardisation of ferritin immunoassays. However, our investigations show that comparison between assay results is still impossible, owing to differences in assay methodology and performance, differences in the specificities of the antibodies and antigens used and other possible interfering substances. We conclude that all kits detect mainly the more basic isoferritins in serum, and that all isoferritins (acidic, intermediate and basic) are systematically underestimated. Since we also showed possible immunological differences between reference or kit standards and serum ferritin, we conclude that the present kits have poor accuracy. To diminish inter-assay variability and to increase the accuracy of serum ferritin determinations, a method is needed that detects all basic, intermediate and acidic isoferritins and measures the true ferritin concentration in serum under normal and pathological circumstances. This reference method can be used to evaluate interference and systematic errors in routine methods. The introduction of a reference method, in combination with the NBSB 80/602 human liver reference preparation, is the second important step towards the accurate standardisation of ferritin immunoassays.
