Selected performance characteristics of the Roche Elecsys testosterone II assay on the Modular analytics E 170 analyzer.

Background: Serum testosterone measurements have utility in diagnosis of clinical conditions characterized by both increased and decreased testosterone concentrations. Studies have indicated that testosterone immunoassays may give inaccurate results for women and children. We evaluated the performance of a second generation testosterone immunoassay from Roche Diagnostics.

Performance characteristics of an immunoturbidimetric assay for lipoprotein-associated phospholipase A2.

Background: Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) is an inflammatory biomarker for coronary heart disease and ischemic stroke risk assessment.

Methods: The Plac turbidimetric immunoassay (TIA) for measurement of Lp-PLA(2) was evaluated for limit of blank, functional sensitivity, dilution linearity, imprecision, interferences, and comparison to an ELISA assay for Lp-PLA(2).

Results: The assay was linear from 100 to 500 microg/l.

Performance characteristics of six homocysteine assays.

Elevated concentrations of homocysteine (Hcy) are associated with a range of disorders. Linearity, imprecision, interference, method comparison, and accuracy were evaluated on the ADVIA Centaur (Siemens Healthcare Diagnostics, Deerfield, IL), ARCHITECT i2000SR (Abbott Diagnostics, Abbott Park, IL), AxSYM (Abbott Diagnostics), and IMMULITE 2000 (Siemens Healthcare Diagnostics) methods and analyzers and the Catch (Equal Diagnostics, Exton, PA) and Diazyme (Diazyme Laboratories, San Diego, CA) methods, both on the Modular P analyzer (Roche Diagnostics, Indianapolis, IN). All methods were linear with maximum deviations from target recoveries of less than 10%.

Performance characteristics of the Access Inhibin A assay.

Background: Second trimester maternal screening using AFP, uE3, hCG, and inhibin A has shown a detection rate for Down's syndrome of 81% with a 5% false positive rate. Inhibin A may also have utility as a serum tumor marker in postmenopausal women with ovarian cancer and men with testicular stromal tumors.

Methods: The Beckman Coulter Access Inhibin A assay was evaluated for limit of blank, dilution linearity, imprecision, interferences, reference intervals, and comparison to an inhibin A ELISA.

Characterization of an immunogenic outer membrane autotransporter protein, Arp, of Bartonella henselae.

Bartonella henselae is a recently recognized pathogenic bacterium associated with cat scratch disease, bacillary angiomatosis, and bacillary peliosis. This study describes the cloning, sequencing, and characterization of an antigenic autotransporter gene from B. henselae.

Evaluation of an enzyme immunoassay for detection of immunoglobulin M antibodies to West Nile virus and the importance of background subtraction in detecting nonspecific reactivity.

Since the introduction of West Nile virus (WNV) in the United States in 1999, several assays have become commercially available to detect antibodies against WNV. Capture enzyme-linked immunosorbent assays (ELISAs) for the detection of WNV-specific immunoglobulin M (IgM) have been approved by the Food and Drug Administration for clinical testing and are available from Focus Diagnostics and PanBio, Inc. The Focus Diagnostics IgM capture ELISA utilizes a background subtraction protocol in order to detect nonspecific reactivity due to rheumatoid factor, heterophile antibodies, or other interfering substances.

Comparison of immunofluorescence antibody testing and two enzyme immunoassays in the serologic diagnosis of malaria.

Background: Serologic testing in malaria has traditionally been done by immunofluorescence antibody testing (IFA), but the use of commercially available enzyme immunoassays (EIAs) has become more widespread.

Methods: We compared IFA with two commercial EIA kits, the Cellabs Pan Malaria CELISA and the Newmarket Malaria EIA. Seventy-five samples from 74 patients with clinically suspected malaria were examined by both EIA kits.

Performance characteristics of seven automated CA 15-3 assays.

Measurements of serum cancer antigen (CA) 15-3 are used to monitor tumor recurrence and treatment of advanced disease. We evaluated the performance characteristics, including limit of detection, linearity, method comparison, and reference intervals, of 7 automated methods for CA 15-3, including the Access 2 (Beckman Coulter, Brea, CA), ADVIA Centaur (Bayer Diagnostics, Tarrytown, NY), ARCHITECT i2000 and AxSYM (Abbott Diagnostics, Abbott Park, IL), Elecsys 2010 (Roche Diagnostics, Indianapolis, IN), IMMULITE 2000 (Diagnostic Products, Los Angeles, CA), and VITROS ECi (Ortho Clinical Diagnostics, Raritan, NJ) assays. The limit of detection for each assay was less than 1.

Performance characteristics of seven automated CA 125 assays.

Cancer antigen 125 (CA 125) is a high-molecular-mass glycoprotein that is used as a tumor marker to monitor disease progression and response to therapy and in early detection of recurrence after treatment for ovarian cancer. The Access 2 (Beckman Coulter, Brea, CA), ADVIA Centaur (Bayer Diagnostics, Tarrytown, NY), ARCHITECT i2000 (Abbott Diagnostics, Abbott Park, IL), AxSYM (Abbott Diagnostics), Elecsys 2010 (Roche Diagnostics, Indianapolis, IN), IMMULITE 2000 (Diagnostic Products, Los Angeles, CA), and VITROS ECi (Ortho Clinical Diagnostics, Raritan, NJ) assays for CA 125 were evaluated for detection limit, dilution linearity, imprecision, correlation, and reference intervals. The maximum average deviation from target recoveries for dilution linearity studies ranged from 3.

Evaluation of a western blot method for the detection of Yersinia antibodies: evidence of serological cross-reactivity between Yersinia outer membrane proteins and Borrelia burgdorferi.

Yersinia enterocolitica and Yersinia pseudotuberculosis have been identified as causative organisms of reactive arthritis in humans. We evaluated a Western blot assay which uses Yersinia outer membrane proteins as antigens for the detection of Yersinia antibodies as a replacement for the complement fixation (CF) assay. Clinical agreement, sensitivity, and specificity were determined by testing 19 positive and 21 negative serum samples by the CF assay, Western blot assay, and enzyme-linked immunosorbent assay (ELISA).

Performance characteristics of four automated natriuretic peptide assays.

Measurement of circulating B-type natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP) can identify patients with heart failure and guide therapy. The limit of detection, linearity, imprecision, method comparison, analytic concordance, and reference intervals of the Access 2 BNP (Biosite, San Diego, CA), ADVIA Centaur BNP (Bayer Diagnostics, Tarrytown, NY), AxSYM BNP (Abbott Diagnostics, Abbott Park, IL), and E170 NT-proBNP (Roche Diagnostics, Indianapolis, IN) methods were evaluated. The Triage meter BNP assay (Biosite) was the comparison method.

Performance characteristics of six third-generation assays for thyroid-stimulating hormone.

Background: Thyroid-stimulating hormone (TSH) is used to detect primary hypo- and hyperthyroidism. Current guidelines for TSH assays recommend a functional sensitivity of < or =0.02 mIU/L.

Oxygen and iron regulation of iron regulatory protein 2.

Iron regulatory protein 2 (IRP2) is a central regulator of cellular iron homeostasis due to its regulation of specific mRNAs encoding proteins of iron uptake and storage. Iron regulates IRP2 by mediating its rapid proteasomal degradation, where hypoxia and the hypoxia mimetics CoCl2 and desferrioxamine (DFO) stabilize it. Previous studies showed that iron-mediated degradation of IRP2 requires the presence of critical cysteines that reside within a 73-amino acid unique region.