ABSTRACT
BACKGROUND: Several unautomated anti-HEV diagnostic tests are presently available. OBJECTIVE: We have evaluated the performance of the new automated VIDAS® ANTI-HEV IgM and IgG assays. STUDY DESIGN: We assessed the reproducibility and cross-reactivity of both VIDAS assays and the analytical sensitivity and linearity of the VIDAS IgG assay. We also tested the VIDAS and comparator assays Wantai IgG and IgM on immunocompetent and immunocompromised patients. Data were analysed according to the infectious profile, with samples from viremic phase (HEV RNA/IgM positive) and post-viremic phase (HEV RNA negative, IgM positive) infections, and uninfected patients (HEV RNA/IgM negative). RESULTS: Within-run reproducibility was <10% and between-run reproducibility was <12% for both assays. We found no cross-reactivity, except for the VIDAS IgG assay in some patients with HBV (1/10) or malaria (3/23) infections and for the VIDAS IgM assay in some HIV-infected patients (1/10). The VIDAS IgG assay was linear over 0.10-10.0 U/mL. Analytical sensitivity of the IgG assay was 0.71 IU/ml (probit analysis). The clinical sensitivity of the VIDAS IgM assay was 97.65% for viremic samples (83/85) and 59.15% (42/71) for post-viremic samples from immunocompetent patients. It was 78.95% (45/57) for acute phase samples and 77.78% (28/36) for post-viremic samples from immunocompromised patients. Specificity was excellent (>99%) in both populations. CONCLUSION: The analytical and clinical performance of the new VIDAS® ANTI-HEV assays was excellent. These rapid, automated assays for detecting HEV antibodies will strengthen the arsenal for diagnosing HEV infections.
Subject(s)
Automation, Laboratory/standards , Hepatitis Antibodies/blood , Hepatitis E/diagnosis , Immunoglobulin G/blood , Immunoglobulin M/blood , Reagent Kits, Diagnostic/standards , Adolescent , Adult , Aged , Aged, 80 and over , Child , Child, Preschool , Cross Reactions , Female , Hepatitis E virus/immunology , Humans , Infant , Male , Middle Aged , Reproducibility of Results , Sensitivity and Specificity , Serologic Tests/standards , Young AdultABSTRACT
Prostate-specific antigen (PSA) is an important marker for the diagnosis and management of prostate cancer. Free PSA has been shown to be more extensively cleaved in sera from benign prostatic hyperplasia patients than in sera from prostate cancer patients. Moreover, the presence of enzymatically activatable PSA was characterized previously in sera from patients with prostate cancer by the use of the specific anti-free PSA monoclonal antibody (mAb) 5D3D11. As an attempt to obtain ligands for the specific recognition of different PSA forms including active PSA, phage-displayed linear and cyclic peptide libraries were screened with PSA coated directly into microplate wells or presented by two different anti-total PSA mAbs. Four different phage clones were selected for their ability to recognize PSA and the inserted peptides were produced as synthetic peptides. These peptides were found to capture and to detect specifically free PSA, even in complex biological media such as sera or tumour cell culture supernatants. Alanine scanning of peptide sequences showed the involvement of aromatic and hydrophobic residues in the interaction of the peptides with PSA whereas Spotscan analysis of overlapping peptides covering the PSA sequence identified a peptide binding to the kallikrein loop at residues 82-87, suggesting that the peptides could recognize a non-clipped form of PSA. Moreover, the PSA-specific peptides enhance the enzymatic activity of PSA immobilized into microplate wells whereas the capture of PSA by the peptides inhibited totally its enzymatic activity while the peptide binding to PSA had no effect in solution. These PSA-specific peptides could be potential tools for the recognition of PSA forms more specifically associated to prostate cancer.
