Ability of TESTPACK ROTAVIRUS enzyme immunoassay to diagnose rotavirus gastroenteritis

A new immune complex dot assay for detection of rotavirus antigen in faeces

A new immune complex dot assay (ICDA) using immune gold/silver staining is described for the sensitive and rapid detection of rotavirus in cell culture and stool specimens. The method involves spotting preformed antigen-antibody complexes onto nitrocellulose paper, followed by incubation with colloidal gold-labelled secondary antibody and silver enhancement. ICDA was sensitive and specific and detected rotavirus antigens over a wide range of concentrations. It was more sensitive than a conventional immunodot assay (CIDA) and two commercial enzyme immunoassays (EIA) based on testing serial dilutions of a positive stool specimen. Of 26 stool specimens tested ICDA detected rotavirus antigen in 17; 14 were positive by Pathfinder Rotavirus EIA, 16 by Testpack Rotavirus EIA, and direct electron microscopy (DEM) detected only 12. The ICDA offers improved sensitivity over commercial EIAs and DEM.

Occurrence of nonspecific reactions among stool specimens tested by the Abbott TestPack rotavirus enzyme immunoassay

Sixty-five stool specimens obtained from children suffering from gastroenteritis were tested for the presence of antigen to rotavirus by the Abbott TestPack Rotavirus (TestPack) enzyme immunoassay kit. The Kallestad Pathfinder enzyme immunoassay, polyacrylamide gel electrophoresis, immune electron microscopy, and virus isolation were utilized as reference assays. Fifty-four specimens were in accord by TestPack and Kallestad Pathfinder. Among 11 discordant specimens positive with TestPack but negative by Kallestad Pathfinder, rotavirus was not identified by polyacrylamide gel electrophoresis, immune electron microscopy, or isolation in primary African green monkey kidney cell cultures. TestPack displayed a performance specificity of 83%. The inordinately high number of stool specimens reported as false-positive by TestPack precludes the incorporation of this antigen detection kit into our routine regimen of diagnostic virologic testing.

Choice of reference assay for the detection of rotavirus in fecal specimens: electron microscopy versus enzyme immunoassay

Two previously demonstrated sensitive and specific enzyme immunoassays (EIAs) for rotavirus, one using polyclonal and monoclonal antisera (TestPack Rotavirus [TPK]; Abbott Laboratories) and the other using only monoclonal anti-rotavirus antibodies (Rotaclone [RTC]; Cambridge BioScience Corporation), were evaluated as potential reference assays for rotavirus testing in comparison with direct negative-staining electron microscopy (EM), the current laboratory standard. Two hundred and seven stool samples collected consecutively during the winter of 1989 from children with acute diarrhea admitted to a ward for infants from 0 to 2 years of age were tested by the EIAs and by EM. TPK specimens were read visually; RTC results were read spectrophotometrically. Specimens with discordant EIA and EM results were further evaluated by a fluorescent focus assay. Specimens positive by EM and those negative by EM but positive by fluorescent focus assay were considered to be positive for rotavirus. Of the 207 stools tested, 35 (17%) were positive for rotavirus by these criteria. EM had a sensitivity of only 80%. Specificities were 100% for RTC and EM and 89% for TPK. These findings indicate that EM, although very specific, is relatively insensitive compared with a highly sensitive monoclonal antibody-based EIA. An EIA with high sensitivity and specificity, such as RTC, is a more appropriate reference standard for rotavirus testing.

Sensitive solid-phase immune electron microscopy double-antibody technique with gold-immunoglobulin G complexes for detecting rotavirus in cell culture and feces

A new solid-phase immune electron microscopy double-antibody colloidal-gold technique (SPIEMDAGT) was developed and compared with direct electron microscopy, direct immune electron microscopy, and enzyme immunoassay for detecting rotavirus. Guinea pig and rabbit antirotavirus antisera were used as capture and detector antibodies, respectively, and goat anti-rabbit immunoglobulin G-gold complexes were employed as a label. Animal rotavirus in cell culture media and human virus in stool specimens were detected by this method. On average, SPIEMDAGT detected 800 times more virus particles than direct electron microscopy and 45 times more particles than direct immune electron microscopy and yielded 20% more positives than enzyme immunoassay. SPIEMDAGT could detect not only viral antigen associated with morphologically recognizable particles but also antigen present when whole virus particles were not visible.

Comparison of three protein A-gold immune electron microscopy methods for detecting rotaviruses

Three immune electron microscopic (IEM) methods employing protein A-colloidal gold (PAG) were compared with direct electron microscopy (DEM) and direct IEM (DIEM) techniques for their abilities to detect simian rotavirus (SA11) and human rotavirus. Using PAG IEM the number of rotavirus particles per grid square was 10 to 50 times and 2 to 5 times higher than observed with DEM and DIEM, respectively. A comparison of sensitivities among the three PAG IEM methods showed that the trapping efficiency for SA11 and human rotavirus was significantly enhanced by a serum-in-agar (SIA) method. The SIA method appeared to be a more reliable and sensitive alternative for detection and quantitation of viral particles.

Comparison of a new rapid test (TestPack Rotavirus) with standard enzyme immunoassay and electron microscopy for the detection of rotavirus in symptomatic hospitalized children

We compared a new, rapid, qualitative test for rotavirus (TestPack Rotavirus; Abbott Laboratories, North Chicago, Ill.) with another enzyme immunoassay (Pathfinder Rotavirus; Kallestad Laboratories, Inc., Austin, Tex.) and electron microscopy to determine its clinical utility in a population of symptomatic hospitalized children. In the first part of the study, 100 frozen stool samples were tested. The results after resolution with a blocking reagent showed a sensitivity of only 50% and a specificity of 88% for TestPack Rotavirus. In the second part of the study, we tested TestPack Rotavirus on 100 fresh, unfrozen samples. The results (sensitivity/specificity) were as follows: TestPack Rotavirus, 95/90%; Pathfinder Rotavirus, 84/98%; direct electron microscopy, 63/100%. Although it was not as sensitive or specific as immune electron microscopy, TestPack Rotavirus was more sensitive than direct electron microscopy or Kallestad Pathfinder Rotavirus. TestPack Rotavirus represents a rapid, qualitative method for the detection of rotavirus in stools of symptomatic children.

Evaluation of Abbott TESTPACK ROTAVIRUS with clinical specimens

TESTPACK ROTAVIRUS was compared with the Pathfinder Rotavirus assay for the detection of rotaviral antigens in feces from 137 patients. The symptomatology and ages of the patients varied from no symptoms to watery diarrhea and from less than 3 months to greater than 60 years of age. The sensitivity and specificity, before resolution, were 89.2 and 90.0%, respectively. After resolution with a blocking reagent, the results were 100% sensitivity and 98.9% specificity. The performance was similar for all age groups and in both symptomatic and asymptomatic patients. Abbott TESTPACK ROTAVIRUS is a rapid (10-min), easy-to-perform assay for the detection of rotaviral antigens and has the sensitivity and specificity of enzyme-linked immunosorbent assays that require several hours to perform.