AUR Memorial Award 1991. Immunogenicity of gadolinium-based contrast agents for magnetic resonance imaging. Induction and characterization of antibodies in animals.

To evaluate the immunogenic potential of gadolinium-based magnetic resonance imaging (MRI) contrast agents, Sprague-Dawley rats were sensitized with gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) dimeglumine and with Gd-DTPA covalently linked to either human serum albumin, dextran, or polylysine. IgG antibodies directed against Gd-DTPA were detected in immune sera by an enzyme-linked immunosorbent assay (ELISA), and were confirmed by competitive inhibition of antibody binding using free Gd-DTPA dimeglumine. Antiserum induced by immunization with human serum albumin-(Gd-DTPA) was characterized by a monophasic competition curve with 50% inhibition (IC50) = 5.5 x 10(-4) M when Gd-DTPA dimeglumine was used as both the well-coating and the displacing agent in a competition ELISA. Antiserum induced by Gd-DTPA dimeglumine alone was characterized by a biphasic competition curve with IC50 = 6.5 x 10(-7) M and 7.9 x 10(-4) M. Antisera obtained after exposure to either dextran-(Gd-DTPA) or polylysine-(Gd-DTPA) were of insufficient titer for characterization. The detection of antibodies specific for Gd-DTPA suggests in vivo protein binding with formation of hapten-carrier conjugates. This hypothesis is supported by increased relaxivity values observed when Gd-DTPA dimeglumine is incubated in serum rather than in water. Gd-DTPA dimeglumine and albumin-(Gd-DTPA) are immunogenic in rats under idealized experimental conditions. Additional studies will be necessary to determine the potential for immunologic response in humans to gadolinium chelates under conditions of exposure inherent in clinical use.     

Comparison of antinuclear antibody testing methods: immunofluorescence assay versus enzyme immunoassay.

Performances of anti-nuclear antibody testing by immunofluorescence assay (ANA-IFA) and enzyme immunoassay (ANA-EIA) were compared in relation to patient diagnosis. A total of 467 patient serum samples were tested by ANA-IFA (Kallestad; Sanofi) and ANA-EIA (RADIAS; Bio-Rad), and their age, sex, diagnosis, disease status, and medications were obtained through chart review. Reference ranges were established by testing 98 healthy blood donor samples. Eighty-six samples came from patients with diffuse connective tissue diseases, including systemic lupus erythematosus, discoid lupus erythematosus, or drug-induced lupus (n = 71); systemic sclerosis, CREST syndrome (calcinosis, Raynaud's phenomenon, esophageal motility abnormalities, sclerodactyly, and telangiectasia), or Raynaud's syndrome (n = 8); Sjögren's syndrome (n = 5); mixed connective tissue disease (n = 5); and polymyositis or dermatomyositis (n = 3). The sensitivity, specificity, positive predictive value, and negative predictive value for ANA-IFA were 87.2, 48.0, 29.1, and 93.9%, respectively, for the reference range of < 1:160. For ANA-EIA, they were 90.7, 60.2, 35.8, and 96.4%, respectively, for the reference range of < 0.9. ANA-EIA offers equivalent sensitivity and higher specificity compared to ANA-IFA.     

Solid-phase Clq-binding fluorescence immunoassay for detection of circulating immune complexes.

A fluorescence immunoassay for detection of immune complexes bound to solid-phase C1q was developed. The method was standardized by using human aggregated immunoglobulin G (IgG) to simulate immune complexes. A linear relationship existed between the concentrations of the aggregated IgG standards and the resulting fluorescent intensity. The method was found to be reproducible and capable of detecting as little as 10 micrograms of aggregated IgG per ml of heat-inactivated human serum. Antigen-antibody complexes prepared in vitro were detectable from equivalence to moderate antigen excess. Endogenous serum C1q inhibited the binding of aggregated IgG to solid-phase C1q. Pretreatment of test sera with EDTA was ineffective in eliminating this competitive effect. Heating the sera at 56 degrees C alleviated, but did not abolish, interference of endogenous C1q. Elevated levels of immune complexes were detectable in sera fro seven of nine patients wit systemic lupus erythematosus, provided the samples were heat inactivated before testing. Heparin and DNA were also found to interfere with the detection of aggregated IgG added to human serum. Assay values were falsely decreased due to competitive inhibition by these anions. Lipopolysaccharides from a variety of bacterial preparations produced no detectable interference. A comparative study was conducted on samples that had previously been tested by fluid-phase C1q-binding radioimmunoassay. The two methods were concordant in assigning normal or elevated levels of immune complexes in 70% of the samples tested. This solid-phase fluorescence immunoassay is proposed as a possible alternative to radioimmunoassay for the detection of circulating immune complexes.     

A comparison of students from main and alternate admission lists at one school: the potential impact on student performance of increasing enrollment.

PURPOSE: If medical schools increase enrollment to meet anticipated physician shortages, more students from alternate lists will likely be accepted. This study compared the performance of alternate- and main-list students during and one year after medical school. METHOD: The authors assessed admission and performance measures for 1,188 students matriculating from 1997-2003 at the University of Kansas School of Medicine. Measures included Medical College Admission Test scores, basic and clinical science grade point averages, United States Medical Licensing Examination Step 1 and Step 2 scores, residency match information, and residency director ratings. Chi-square analyses, proportional analyses, and independent t-tests were performed. RESULTS: The results indicated that both the admission measures and performance of alternate-list students were generally lower than main-list students, but the differences were small and probably not meaningful. CONCLUSIONS: As long as the applicant pool does not substantially change from its current makeup, increasing enrollment by accepting more students from alternate lists may not adversely affect overall student performance.     

Simultaneous detection of antibodies to cytomegalovirus and herpes simplex virus by using flow cytometry and a microsphere-based fluorescence immunoassay.

A sensitive assay for the simultaneous detection of anti-cytomegalovirus and anti-herpes simplex virus antibodies was developed. Two different sizes of polystyrene microspheres were coated with purified viral antigens. Human antiviral antibodies were detected with a biotin-streptavidin amplification procedure with phycoerythrin as the fluorescent label. Microsphere-associated fluorescence was quantitated with a flow cytometer. Sixteen percent of samples initially scored as seronegative for cytomegalovirus and 35% of samples initially scored as seronegative for herpes simplex virus by conventional assays were clearly found positive by the microsphere technique. This flow cytometric assay can simultaneously detect several specific antibodies at levels which are below the sensitivity of standard assays. The dynamic range of this assay is at least sixfold greater than that of enzyme immunoassays. This technique is amenable to numerous serologic assays and could greatly expand the clinical laboratory applications of flow cytometry.     

Aligning compensation with education: design and implementation of the Educational Value Unit (EVU) system in an academic internal medicine department.

The authors report the development of a new metric for distributing university funds to support faculty efforts in education in the department of internal medicine at the University of Kansas School of Medicine. In 2003, a committee defined the educational value unit (EVU), which describes and measures the specific types of educational work done by faculty members, such as core education, clinical teaching, and administration of educational programs. The specific work profile of each faculty member was delineated. A dollar value was calculated for each 0.1 EVU. The metric was prospectively applied and a faculty survey was performed to evaluate the faculty's perception of the metric. Application of the metric resulted in a decrease in university support for 34 faculty and an increase in funding for 23 faculty. Total realignment of funding was US$1.6 million, or an absolute value of US$29,072 +/- 38,320.00 in average shift of university salary support per faculty member. Survey results showed that understanding of the purpose of university funding was enhanced, and that faculty members perceived a more equitable alignment of teaching effort with funding. The EVU metric resulted in a dramatic realignment of university funding for educational efforts in the department of internal medicine. The metric was easily understood, quickly implemented, and perceived to be fair by the faculty. By aligning specific salary support with faculty's educational responsibilities, a foundation was created for applying mission-based incentive programs.