Hepcidin-25 vs. conventional clinical biomarkers in the diagnosis of functional iron deficiency.

OBJECTIVES: As hepcidin-25 is considered as a key regulator of human iron homoeostasis, this study aimed to compare this parameter with conventional biomarkers and diagnostic tools of iron deficiency (ID). METHODS: In total, 233 hospitalised adult patients, who underwent routine blood testing for ID, were included. All subjects were investigated for hepcidin-25, reticulocyte haemoglobin content (CHr), soluble transferrin receptor (sTfR)/log ferritin ratio (i.e. Thomas plot), sTfR, ferritin, transferrin saturation (TSAT), C-reactive protein (CRP) and for complete blood cell count. Functional ID was defined as a CHr < 28 pg. Separate logistic regression models were calculated with all potential biomarkers to evaluate and compare the predictive performance with respect to functional ID in patients without (CRP ≤ 0.5 mg/dL) and with (CRP > 0.5 mg/dL) acute-phase reaction, respectively. RESULTS: One hundred seventeen patients with CRP > 0.5 mg/dL showed a distinctly higher hepcidin-25 median value [35.60 (range: 4.27-80.03) ng/mL] as compared to 116 patients with CRP ≤ 0.5 mg/dL [18.55 (range: 3.77-73.01) ng/mL]. With respect to functional ID, sTfR/log ferritin ratio and sTfR were of better positive predictive value (PPV) (sTfR/log ferritin ratio: 58.33% and 70.83%; sTfR: 60.00% and 60.00%) than when compared to hepcidin-25 (PPV: 37.74% and 42.86%) and ferritin (PPV: 27.54% and 46.15%) in both subgroups. CONCLUSIONS: The sTfR/log ferritin ratio, as well as sTfR, were better predictors of functional ID in patients with and without acute-phase reaction as compared to hepcidin-25 and ferritin.

Method evaluation study of a new generation of vitamin D assays.

INTRODUCTION: Recently several diagnostic manufacturers have launched new 25-hydroxy-vitamin D (25[OH]D) assays, which are aligned to the National Institute of Standards and Technology (NIST) Standard Reference Materials (SRM) (NIST, Gaithersburg, Maryland). The aim of this study was to compare the performance of one liquid chromatography-tandem mass spectrometry (LC-MS/MS) method, one enzyme linked immunosorbent assay (ELISA), and one recalibrated and previous version of a chemiluminescence immunoassay (CLIA). MATERIAL AND METHODS: Serum-aliquots of 198 patient samples from routine 25(OH)D analysis were measured by the ClinMass® LC-MS/MS Complete Kit (RECIPE Chemicals+Instruments GmbH, Munich, Germany), the ORGENTEC 25(OH)D3/D2 ELISA (ORGENTEC Diagnostika GmbH, Mainz, Germany), the recalibrated Immunodiagnostic Systems (IDS)-iSYS 25(OH)DS and the previous used IDS-iSYS 25(OH)D CLIA (Immunodiagnostic Systems Ltd, Boldon, United Kingdom). Bland-Altman and Deming regression analyses were calculated for methods comparison of all tested 25(OH)D assays. The LC-MS/MS method was defined as the reference method. Within-run and between-run precision measurements were performed for all methods with three different concentration levels. RESULTS: Compared to the LC-MS/MS method, the new IDS-iSYS 25(OH)DS and ORGENTEC 25(OH)D3/D2 assay demonstrated mean relative biases of 16.3% and 17.8%. The IDS-iSYS 25(OH)D assay showed the lowest mean bias of 1.5%. Deming regression analyses of the recalibrated IDS-iSYS 25(OH)DS and the ORGENTEC 25(OH)D3/D2 assay showed proportional differences, when compared to the reference method. All assays showed a within-run and between-run imprecision of ≤20% at each of the evaluated concentration levels. CONCLUSIONS: The evaluated standardized immunoassays and LC-MS/MS are useful methods for measuring 25(OH)D serum-levels in clinical laboratories.