Validation of a competitive ELISA assay for the quantification of human serum hepcidin.

BACKGROUND: Hepcidin-25 is a potential marker for iron disorders with a demand for accessible assays. This study aimed to evaluate a commercial competitive enzyme-linked immunosorbent assay (cELISA) for hepcidin quantitation. METHODS: Serum samples; 95 healthy subjects (HS), six patients with iron deficiency (ID), 84 patients with liver disorders (LD) and 220 hemodialysis patients (HD), were analyzed. Controls were used for imprecision, while accuracy was evaluated by quantitating hepcidin-25 with LC-MS/MS in 149 samples. Cross-reactivity for hepcidin-20 and hepcidin-22 was tested. Hepcidin-mRNA expression in 37 liver biopsies was measured. RESULTS: S-hepcidin ranged from 8-76 and 2-31 µg/L in healthy men and women. Levels in ID, LD and HD significantly differed from HS. Total coefficients of variation (CV) for controls were 24% and 22%. Within-sample CV was 10%. Despite a good correlation with LC-MS/MS (r = 0.89), the cELISA showed higher values and detected hepcidin-20 and hepcidin-22. Hepcidin-mRNA correlated well with S-hepcidin using cELISA and LC-MS/MS (r = 0.69 and 0.64). CONCLUSIONS: The correlation with LC-MS/MS is good and the examined kit can differentiate between patient groups although it is not specific for hepcidin-25. Considering ELISA's capacity to readily be set up, the investigated kit can be applied. Specific reference ranges are required.

The Alzheimer's Association external quality control program for cerebrospinal fluid biomarkers.

BACKGROUND: The cerebrospinal fluid (CSF) biomarkers amyloid ß (Aß)-42, total-tau (T-tau), and phosphorylated-tau (P-tau) demonstrate good diagnostic accuracy for Alzheimer's disease (AD). However, there are large variations in biomarker measurements between studies, and between and within laboratories. The Alzheimer's Association has initiated a global quality control program to estimate and monitor variability of measurements, quantify batch-to-batch assay variations, and identify sources of variability. In this article, we present the results from the first two rounds of the program. METHODS: The program is open for laboratories using commercially available kits for Aß, T-tau, or P-tau. CSF samples (aliquots of pooled CSF) are sent for analysis several times a year from the Clinical Neurochemistry Laboratory at the Mölndal campus of the University of Gothenburg, Sweden. Each round consists of three quality control samples. RESULTS: Forty laboratories participated. Twenty-six used INNOTEST enzyme-linked immunosorbent assay kits, 14 used Luminex xMAP with the INNO-BIA AlzBio3 kit (both measure Aß-(1-42), P-tau(181P), and T-tau), and 5 used Meso Scale Discovery with the Aß triplex (AßN-42, AßN-40, and AßN-38) or T-tau kits. The total coefficients of variation between the laboratories were 13% to 36%. Five laboratories analyzed the samples six times on different occasions. Within-laboratory precisions differed considerably between biomarkers within individual laboratories. CONCLUSIONS: Measurements of CSF AD biomarkers show large between-laboratory variability, likely caused by factors related to analytical procedures and the analytical kits. Standardization of laboratory procedures and efforts by kit vendors to increase kit performance might lower variability, and will likely increase the usefulness of CSF AD biomarkers.

Lateral elements inside synaptonemal complex-like polycomplexes in ndt80 mutants of yeast bind DNA.

The synaptonemal complex (SC) keeps the synapsed homologous chromosomes together during pachytene in meiotic prophase I. Structures that resemble stacks of SCs, polycomplexes, are sometimes found before or after pachytene. We have investigated ndt80 mutants of yeast, which arrest in pachytene. SCs appear normal in spread chromosome preparations, but are only occasionally found in intact nuclei examined in the electron microscope. Instead, large polycomplexes occur in almost every ndt80 mutant nucleus. Immunoelectron microscopy using DNA antibodies show strong preferential labeling to the lateral element parts of the polycomplexes. In situ hybridization using chromosome-specific probes confirms that the chromosomes in ndt80 mutants are paired and attached to the SCs. Our results suggest that polycomplexes can be involved in binding of chromosomes and possibly also in synapsis.