Laboratory performance in HTLV-I/II analysis.

BACKGROUND: Since 1989, the CDC's Model Performance Evaluation Program has shipped samples to voluntary participant laboratories that test for HTLV antibodies. Each laboratory tests the well-characterized samples, reports the results, and provides information about its testing practices. The data from 15 performance survey periods are reported here. STUDY DESIGN AND METHODS: Multiple logistic regression was used to analyze all data from 15 survey periods from 1989 through 1996. RESULTS: The mean analytic sensitivity for EIA was 99.2 percent per survey period (range, 96-100%), the mean analytic specificity was 97.8 percent (75.6-100%), and the overall accuracy was 88.8 percent (63.8-100%). The mean analytic sensitivity for Western blot was 88.8 percent (75.6-100%); the mean analytic specificity was 95.7 percent (86.7-100%), and the overall accuracy was 91.1 percent (78.1-100%). CONCLUSIONS: Statistical analyses suggested associations between performance and both the retroviral serologic status of the sample and the analytical testing method. Western blot accuracy was associated with weekly testing volume. In early survey periods, performance problems were noted in the analysis of samples from donors with concomitant HTLV and HIV infections and those from donors who were positive for HTLV-II. Technological developments in test methods, such as the addition of recombinant antigens, appeared to have improved the laboratory performance of specific testing methods.

Impact of quality control on accuracy in enzyme immunoassay testing for human immunodeficiency virus type 1 antibodies.

OBJECTIVE: To assess use of quality control (QC) material, supplemental to internal kit controls (calibrators), as protection against errors in enzyme immunoassay testing for human immunodeficiency virus type 1 antibodies. DESIGN: From August 1994 to January 1996, enzyme immunoassay testing accuracy was assessed for laboratories participating in the Centers for Disease Control and Prevention Model Performance Evaluation Program that provided information regarding their use of QC material. Error rates were examined for human immunodeficiency virus type 1 antibody-negative, strongly positive, and weakly positive samples. RESULTS: The overall error rate with QC (2.20%) was significantly (P = .0023) lower than the error rate without QC (2.90%). With QC use there was a significant reduction in the relative risk of error for negative (P = .014) and weakly positive (P = .0067) samples. After multivariate analysis, use of QC lowered overall error rate by 29% (P = .0009). Laboratories not using QC were at increased risk of systematic error. Following the Clinical Laboratory Improvement Amendments of 1988 guidelines for QC material was relatively more protective against error than lower frequencies/number of levels. CONCLUSIONS: Using QC protected against errors in enzyme immunoassay testing for human immunodeficiency virus type 1 antibodies. Two levels of QC should be used with each run as mandated by the Clinical Laboratory Improvement Amendments of 1988.

Analytic sensitivity and specificity of enzyme immunoassay results in testing for human immunodeficiency virus type 1 antibody.

In 1986, a performance evaluation program at the Centers for Disease Control was implemented to assess the quality of performance of laboratories testing for human immunodeficiency virus type 1 antibody and to identify problems that occur during the testing process. Laboratories participating in the Centers for Disease Control Model Performance Evaluation Program for human immunodeficiency virus type 1 antibody testing furnished enzyme immunoassay results after they tested performance evaluation panels that were sent to them in August and November 1989. The panels consisted of 10 individual samples containing antibody-negative and antibody-positive samples, some of which were duplicates. Not all laboratories received the same panel of samples. Low false-negative and false-positive rates, as well as high intrashipment and intershipment reproducibility, indicate that most laboratories did not experience difficulty in testing performance evaluation samples sent to them in August and November 1989.

Human T-lymphotropic virus type I/II. Status of enzyme immunoassay and western blot testing in the United States in 1989 and 1990.

In three performance evaluation surveys, panels that consisted of human T-lymphotropic virus type I or type II (HTLV-I/II) antibody-positive and -negative plasma samples were mailed to laboratories that voluntarily participated in the Centers for Disease Control Model Performance Evaluation Program. Donor samples were identical among surveys. In each survey, more than 98% of the laboratories reported enzyme immunoassay (EIA) test results; about 11% also reported results of Western blot (WB) testing. Variation in analytic sensitivity (96.7% to 99.4%) and specificity (98.3% to 99.5%) of EIA tests was noted in the three surveys. For WB testing, no nonreactive interpretations were reported for HTLV-I/II antibody-positive samples in any survey; however, indeterminate interpretations were reported for 35.2% to 40.7% of the WB tests that were performed on HTLV-I/II antibody-positive samples. More than 95% of these indeterminate WB test interpretations were reported for HTLV-II antibody-positive samples. Although HTLV-I/II antibody tests are generally sensitive and specific, their accuracy could be further improved by increasing the specificity of EIA tests and the sensitivity of WB tests.

Relationship between performance in three of the Centers for Disease Control microbiology proficiency testing programs and the number of actual patient specimens tested by participating laboratories.

The performance of laboratories enrolled in three of the Centers for Disease Control microbiology performance evaluation programs was studied in relation to the number of actual patient specimens tested by the laboratories. Laboratories were grouped according to the number of specimens tested weekly to compare performance among the groups. Results of the study showed that laboratories, as a group, that tested large numbers of specimens performed better than laboratories that tested small numbers. The infrequency of performing certain tests or identifying certain microbial species can be an important factor in laboratory error. One strategy for laboratories that cannot resolve internal problems associated with low testing volumes would be to limit their testing to procedures that are done well.

Rapid and reliable method for production of a specific Paracoccidioides brasiliensis immunodiffusion test antigen.

Previously published methods to produce Paracoccidioides brasiliensis antigens for serological tests have yielded antigens of inconsistent quality and have involved the use of special semisynthetic media and growth periods of 1 to 3 months to yield suitable reagents. A simple procedure that uses commercially available potato glucose agar and either SABHI broth (Difco Laboratories) or Trypticase soy broth (BBL Microbiology Systems) inoculated with the mycelial form of P. brasiliensis consistently yielded high-titer antigens in 2 weeks or less. This new method permits the almost exclusive production of an antigen identical to the specific E antigen described by Yarzabal (Yarzabal et al., Sabouradia 14:275-280, 1976) and the apparently equivalent specific antigen 1 described by Restrepo and Moncada (A. Restrepo and L. H. Moncada, Appl. Microbiol. 28:138-144, 1974). In the immunodiffusion test, the rapidly produced antigen demonstrated a sensitivity of 90% by detecting antibody in sera from 103 of 114 proven cases of paracoccidioidomycosis. The specificity of this antigen was 100% because none of 139 sera from patients with heterologous mycotic diseases demonstrated diagnostic precipitins against the P. brasiliensis antigen. In the complement fixation tests, the rapidly produced antigen was not as suitable as the one prepared by the method of Restrepo-Moreno and Schneidau (A. Restrepo-Moreno and J. D. Schneidau, Jr., J. Bacteriol. 93:1741-1748, 1967).

Microimmunodiffusion test for nocardiosis.

Sera from 71 patients with culturally proven nocardiosis were tested for precipitins against a pool of Nocardia asteroides and N. brasiliensis culture filtrates and against antigens from the supernatant of homogenized N. asteroides cells. A human nocardiosis case serum was used as a reference. Sera from 56 of the 71 cases were reactive with either the culture filtrate antigen, the homogenate antigen, or both antigens, resulting in an overall sensitivity of 79%. Sera from 35 of the patients (49%) were positive with the homogenate antigens, and 28 (39%) showed bands of identity with the reference serum. Sera from 50 nocardiosis cases (70%) were positive with the pooled culture filtrate antigens, and 29 (41%) produced bands of identity with the reference serum. Of 89 sera from patients with various systemic mycotic diseases, tuberculosis, or actinomycosis, 24 (27%) were positive with the nocardial homogenate antigens and 4 (4.5%) showed precipitin bands of identity. Thirty-five of the 89 sera (42%) were positive with the nocardial culture filtrate antigens, and 6 (6.7%) showed bands of identity. The majority of sera demonstrating false-positive reactions were from tuberculosis and actinomycosis cases. One of seven sera from well individuals produced a precipitin band with the culture filtrate antigen, but this was not a band of identity with reference serum. These antigens did not distinguish antibodies from patients with N. asteroides, N. brasiliensis, or N. cavia infections.

Characterization of immunoglobulin classes of human antibodies to cryptococcus neoformans.

Immunoglobulin G (IgG), immunoglobulin M (IgM) and immunoglobulin A (IgA) levels were determined by radial immunodiffusion techniques in sera from 11 patients with cryptococcosis. Most specimens showed increased levels of IgM. Studies with fluorescein-labeled monospecific antihuman IgG and IgM, however, indicated that IgG was the immunoglobulin reactive in the indirect fluorescent antibody (IFA) test. In addition, cross-reacting sera from mycotic infections other than cryptococcosis were also shown to contain IFA antibodies of the IgG class. Sera treated with 2-mercaptoethanol continued to react in both the IFA test and the tube agglutination test. No correlation could be established between IgG AND IgM concentrations and serological reactivity in the sera evaluated in this study.

Comparative evaluation of five serological methods for the diagnosis of sporotrichosis.

The diagnosis of sporotrichosis can be time consuming. Serological procedures could facilitate the rapid and accurate diagnosis of this disease. A slide latex agglutination (SLA) test for sporotrichosis was developed and compared with the tube agglutination (TA), complement fixation (CF), and immunodiffusion (ID) tests in the serological study of 80 proven human cases of sporotrichosis representing the cutaneous, subcutaneous, and extracutaneous forms of the disease. In addition, the indirect fluorescent antibody (IFA) technique was applied to 61 case sera. In the SLA test, latex particles sensitized with culture filtrate antigens from the yeast form of Sporothrix schenckii (B 959) detected 94% of the cases, as compared to 96% of the cases detected by the TA test, 68% by the CF test, and 56% by the ID test. The IFA test detected 90% of the 61 cases. The SLA and ID tests were specific, showing no reactions with sera from 86 persons with no disease or with diseases other than sporotrichosis. Because of its sensitivity, specificity, ease of performance, and ability to provide results in 5 min, the SLA test is highly recommended for routine use in the clinical laboratory.

Comparison of a newly developed latex agglutination test and an immunodiffusion test in the diagnosis of systemic candidiasis.

A newly developed latex agglutination (LA) test and a modified immunodiffusion (ID) test were evaluated. The antigen used was a homogenate of Candida albicans. A total of 167 antisera were employed in the evaluation. They included 36 sera from clinically well persons; 78 from patients with various clinical forms of candidiasis; 52 from patients with proven cases of aspergillosis, blastomycosis, coccidioidomycosis, cryptococcosis, histoplasmosis, nocardiosis, paracoccidioidomycosis, sporotrichosis, and tuberculosis; and one serum from a patient with toruloposis. Use of the LA test in conjunction with the ID test permitted the detection of more than 90% of 43 proven candidiasis cases. Of all the heterologous cases and normal human sera tested, LA reactions were noted with 3 of 10 cryptococcosis case specimens, 1 of 9 tuberculosis case specimens, and with the torulopsemia case serum. In contrast, the only heterologous serum reactive in the ID test was that from the patient with torulopsemia. Torulopsis glabrata and C. albicans antisera gave identical reactions in LA and ID tests with T. glabrata or C. albicans antigens. ID tests with selected antigens, however, permitted differentiation of rabbit and human T. glabrata antibody from that of C. albicans antibody. Six different precipitins were recognized with the C. albicans antigens. The occurrence of multiple precipitin lines and high LA titers was suggestive of severe candidiasis. The LA test, in contrast to the ID test, appeared to have prognostic value. Together, the LA and ID tests provided a simple, rapid, and accurate means of detecting and monitoring infections by species of Candida.