Identification of performance problems in a commercial human immunodeficiency virus type 1 enzyme immunoassay by multiuser external quality control monitoring and real-time data analysis.

In June 2005, a pilot program was implemented in Canadian laboratories to monitor the performance of the Abbott human immunodeficiency virus types 1 and 2 (HIV-1/2) gO enzyme immunoassay (EIA). Two different external quality control (QC) reagents and a "real-time" software analysis program were evaluated. In November 2005, higher-than-expected calibrator rate values in these kits were first reported at the Ontario Ministry of Health (Etobicoke), followed by the Alberta Provincial Public Health Laboratory (Edmonton and Calgary) and others. These aberrations were easily and readily tracked in "real time" using the external QC reagents and the software program. These high calibrator values were confirmed in Delkenheim, Germany, by Abbott, and a manufacturing change was initiated beginning with lot 38299LU00, which was distributed to laboratories in Canada in April 2006. However, widespread reports of calibrator failure by laboratories outside Canada were made in March 2006. In April 2006, Abbott Diagnostics initiated a level III investigation to identify the root cause, which was prolonged storage, under uncontrolled storage conditions, of the raw material used in the manufacture of the matrix cells. To the best of our knowledge, this is the first example of a program in Canada for serological testing that combines a common external QC reagent and a "real-time" software program to allow laboratories to monitor kit performance. In this case, external QC monitoring helped identify and confirm performance problems in the Abbott HIV-1/2 gO EIA kit, further highlighting the benefit of implementing such a program in a national or multilaboratory setting for laboratories performing diagnostic and clinical monitoring testing.

Use of immunoglobulin G avidity assays for differentiation of primary from previous infections with West Nile virus.

Since its introduction in 1999, West Nile virus (WNV) infections have spread rapidly across the North American continent. Diagnosis of acute WNV infection by detection of WNV-specific immunoglobulin M (IgM) is complicated by the persistence of detectable IgM for more than 1 year in some patients. IgG antibody avidity testing was assessed as a supplemental assay in the diagnosis of current infections. Three groups of serum samples were assayed in parallel by two different IgG avidity test systems (indirect immunofluorescence test [IIFT] and prototype enzyme-linked immunosorbent assay [ELISA]; EUROIMMUN, Luebeck, Germany). Group I (40 sera taken between 2 and 9 days after the onset of influenza-like symptoms) and group II (40 sera taken between 10 and 43 days after onset) were acute and convalescent specimens from patients with a positive anti-WNV IgM test (ELISA; Focus Diagnostics, Cypress, CA). Group III consisted of 43 patient sera collected between 6 and 12 months after infection. IgG antibodies specific for WNV were detected in 38% (ELISA) and 50% (IIFT) of group I sera, in 90% (ELISA and IIFT) of group II sera, and in 100% (ELISA and IIFT) of group III sera. Low-avidity IgG antibodies were demonstrated in 86% (ELISA) and 95% (IIFT) of IgG-positive patient samples taken between 2 and 43 days after the onset of symptoms (groups I and II). High-avidity IgG antibodies were detected in 100% of group III sera obtained 6 months or more after the onset of symptoms (ELISA and IIFT). IgG avidity tests for WNV infections are rapid and simple to perform. The determination of IgG avidity provides additional diagnostic certainty in differentiating between recently acquired and previous infections with WNV.

A comparison of the Genie and western blot assays in confirmatory testing for HIV-1 antibody.

The Genie HIV-1/2 kit (Sanofi Diagnostics Pasteur, Montreal, Quebec), a synthetic-peptide solid-phase enzyme immunoassay, was evaluated as a confirmatory assay for HIV-1 antibodies in comparison with Western blot (BioRad, Hercules, CA, USA) on 50 stored HIV-1 antibody-positive sera and the 137 sera yielding repeated positive results in the conventional EIA screen out of 13405 fresh patient sera from Saskatchewan in 1993. The stored HIV-1-positive sera were uniformly positive in the Genie test. Of the 137 EIA screen-positive sera, 33 were uniformly positive and 64 were uniformly negative in Genie and Western blot; 36 were Genie-negative and indeterminate by Western blot; and four were Genie indeterminate, of which one was negative and three were indeterminate by Western blot. All HIV-1 Western blot-indeterminate and Genie-interdeterminate sera were negative in radio-immunoprecipitation assay (RIPA) and Western blot for HIV-1 and HIV-2 antibodies performed by a reference laboratory. Genie gave an accurate definitive result for 97% of EIA positive sera compared with 71% for Western blot. There was excellent correlation between Genie, Western blot and RIPA results. However, the Genie assay was faster, less costly and yielded fewer indeterminate results than Western blot in confirmatory testing for HIV-1 antibodies.