Novel Recombinant-Antigen Enzyme Immunoassay for Serological Diagnosis of Syphilis

Enzyme immunoassay (EIA) is an ideal method for screening large numbers of patients for syphilis. We evaluated a novel immune-capture EIA (ICE Syphilis; Murex Diagnostics) that uses three recombinant Treponema pallidum antigens (TpN15, TpN17, and TpN47) and compared the results with those obtained by the native T. pallidum antigen EIA (Captia SelectSyph-G; Centocor) that we currently use for the serodiagnosis of syphilis. Specificity was evaluated by screening 1,184 unselected serum specimens in parallel by the ICE Syphilis and SelectSyph-G assays, while sensitivity was tested with a panel of 101 serum specimens containing antitreponemal antibodies (treated and untreated) from patients with various stages of infection. The specificity of the ICE Syphilis EIA (99.8%) on screening was significantly higher (P < 0.02) than that of the SelectSyph-G EIA (99.2%). The sensitivity of the ICE Syphilis EIA was significantly higher (P < 0.01) than that of the SelectSyph-G EIA on both initial (99 versus 91.4%) and repeat (100 versus 92.4%) testing. The ICE Syphilis EIA was also significantly more sensitive (P < 0.01) than the fluorescent treponemal antibody-abs (92.4%) but not the T. pallidum hemagglutination assay (97.1%). Sera containing antitreponemal antibodies gave a much higher antibody index (absorbance of test serum/kit cutoff) by the ICE Syphilis EIA than by the SelectSyph-G EIA. This combined with the overall high sensitivity makes the ICE Syphilis EIA an ideal test for excluding or detecting treponemal infection in human immunodeficiency virus (HIV)-infected patients. The ICE Syphilis EIA was positive with sera from all 15 HIV-infected patients in the study, whereas sera from 3 HIV-infected patients were negative by the SelectSyph-G EIA. We conclude that the high sensitivity and specificity of the ICE Syphilis EIA and its suitability for automation make it an ideal screening test.     

Comparison of two rapid human immunodeficiency virus (HIV) assays, Determine HIV-1/2 and OraQuick Advance Rapid HIV-1/2, for detection of recent HIV seroconversion

Modified protocols of two rapid tests were compared with a less sensitive (LS) (detuned) enzyme immunoassay (EIA) for their abilities to distinguish recent human immunodeficiency virus (HIV) seroconversion from long-term infections. The results for samples from 100 HIV-positive patient that had previously been tested by the Vironostika LS EIA had a 97% concordance with the results of the Determine HIV 1/2 assay and 93% concordance with those of the OraQuick HIV 1/2 assay.     

Comparison of the human immunodeficiency virus (HIV) type 1-specific immunoglobulin G capture enzyme-linked immunosorbent assay and the avidity index method for identification of recent HIV infections

The sensitivity and specificity of the human immunodeficiency virus (HIV) type 1-specific immunoglobulin G capture enzyme-linked immunosorbent assay (BED-CEIA) were compared with those of the avidity index method to identify recent HIV infection using a panel of 148 samples (81 patients) representing durations of infection ranging from 0 to 222 weeks. The results from the two tests were similar (sensitivity of 80% versus 74% [P = 0.53]; specificity of 86% versus 82% [P = 0.67]).     

Evaluation of a Rapid Immunochromatographic Test for Detection of Antibodies to Human Immunodeficiency Virus

A new immunochromatographic rapid test, Determine HIV-1/2, for the detection of antibodies to human immunodeficiency virus type 1 (HIV-1) and HIV-2 in human whole blood, serum, and plasma was evaluated. Determine HIV-1/2 is a sandwich immunoassay and uses a nitrocellulose strip with a capture site for the patient’s results and a procedural control site to confirm the validity of the assay. The results can be read visually, and a positive result is indicated by the formation of a red line within 15 min after sample application. The test showed 100% sensitivity for HIV-1 with 102 whole-blood, 152 serum, and 144 plasma samples obtained from Ramathibodi Hospital, Bangkok, Thailand. The sensitivity of the test for HIV-2 was 100% with 100 serum or plasma samples obtained from Ivory Coast. The sensitivity of the test with 4 anti-HIV-1 seroconversion panels from Boston Biomedica Inc. was equivalent to or better than those of another agglutination assay with serum or plasma and the enzyme immunoassay licensed by the U.S. Food and Drug Administration. The specificity was 100% with 367 sets of whole-blood, serum, and plasma samples from Ramathibodi Hospital. This method had an analytical sensitivity for the detection of HIV-1 equivalent to or better than that of another agglutination assay with serum or plasma. This test had an analytical sensitivity for the detection of HIV-1 better than that of another immunochromatographic test with whole blood. This evaluation demonstrated the excellent performance of this immunochromatographic test with EDTA-anticoagulated whole-blood, serum, and plasma samples. We conclude that this test is suitable for use in emerging countries and is an excellent alternative to HIV antibody testing at remote sites, as well as in traditional laboratories.     

Validation, performance under field conditions, and cost-effectiveness of Capillus HIV-1/HIV-2 and determine HIV-1/2 rapid human immunodeficiency virus antibody assays using sequential and parallel testing algorithms in Tanzania

Rapid human immunodeficiency virus (HIV) antibody tests support the effort to expand access to HIV testing and counseling services in remote, rural, and poor parts of the world. We validated the Capillus HIV-1/HIV-2 (Trinity Biotech PLC, Bray, County Wicklow, Ireland) and Determine HIV-1/2 (Abbott Laboratories, Abbott Park, IL) rapid tests in a reference laboratory using patient samples from Tanzania and evaluated the performance of the tests under field conditions in northern Tanzania. We used the resulting data to study sequential and parallel testing algorithms. In the validation study, sensitivity, specificity, the predictive value of a positive test (PV⁺), and the predictive value of a negative test (PV⁻) were all 100% for Capillus and Determine. In the field evaluation among 12,737 clients, sensitivity, specificity, PV⁺, and PV⁻ were 99.7%, 99.8%, 98.7%, and 99.9%, respectively, for Capillus and 99.6%, 99.9%, 99.5%, and 99.9%, respectively, for Determine. A sequential testing algorithm that did not confirm a negative initial Capillus result with a Determine result cost $7.77 per HIV diagnosis but missed 0.3% of HIV infections. A sequential testing algorithm that did not confirm a negative initial Determine result with a Capillus result cost $7.64 per HIV diagnosis but missed 0.4% of HIV infections. A parallel testing algorithm cost $13.46 per HIV diagnosis but detected more HIV-infected clients.     

Comparison of Performance and Cost-Effectiveness of Direct Fluorescent-Antibody, Ligase Chain Reaction, and PCR Assays for Verification of Chlamydial Enzyme Immunoassay Results for Populations with a Low to Moderate Prevalence of Chlamydia trachomatis Infection

Many laboratories use a commercial enzyme immunoassay (EIA) with verification testing to diagnose Chlamydia trachomatis infections in an effort to contain costs. This study was designed to compare the performance and cost-effectiveness of direct fluorescent-antibody assay (DFA), commercial PCR, and ligase chain reaction (LCR) for the verification of EIA results. Cervical specimens were screened by EIA. DFA, PCR, and LCR were compared as verification tests for EIA-reactive specimens and negative greyzone (NGZ) specimens at 50% below the cutoff value. These samples were also tested by in-house PCR, which was used in the analysis of verification results. A total of 477 (7%) of 6,571 samples were reactive or within the NGZ. EIA results with verification by DFA testing (EIA/DFA results) agreed with 93% of the true results compared with 97% for EIA/PCR results for one set of 242 samples; there was 97% agreement with true results for EIA/DFA results versus 95% for EIA/LCR results for another set of 235 samples. Ten samples were false positive by LCR. Time and costs were equivalent for EIA with the DFA, PCR, or LCR as the verification test but were two- to threefold greater for PCR or LCR alone than for EIA with verification. Since it is important to balance cost containment with public health objectives, DFA, PCR, and LCR as EIA verification tests for cervical samples offer acceptable sensitivities and specificities at reasonable cost for low- to moderate-risk populations and therefore can be extended to a broader spectrum of at-risk populations.     

Utility of Galactomannan Enzyme Immunoassay and (1,3) β-d-Glucan in Diagnosis of Invasive Fungal Infections: Low Sensitivity for Aspergillus fumigatus Infection in Hematologic Malignancy Patients

Previous studies have reported that galactomannan (GM) enzyme immunoassay and 1,3 beta-glucan (BG) assay may be useful diagnostic tools, but their sensitivities are variable. We compared the performances of both tests. Between October 2002 and May 2005, 82 patients were prospectively monitored for 12 weeks. A total of 414 samples were tested by GM assay and 409 samples were tested by BG assay for the following four groups of patients: those with invasive aspergillosis (IA), those with other mold infections (Fusarium, scedosporium, zygomycosis, etc.), those with candidemia, and control patients. Blood samples were obtained twice on week 1 and once every other week for a total of 12 weeks. Patients in the invasive fungal infection groups had comparable risk factors. The sensitivity of the GM test was significantly higher for patients with IA due to non-fumigatus Aspergillus species than for patients with IA due to Aspergillus fumigatus (49% versus 13%; P < 0.0001) or with other mold infections (49% versus 6%; P < 0.0001). However, the sensitivity range (47% to 64%) and specificity (88%) of the BG assay were comparable among all patients tested, regardless of the infecting pathogen. The performance of GM-based diagnosis appears to be better for detecting non-fumigatus Aspergillus species. The diagnostic marker BG was shown to have a higher sensitivity than that of GM in detecting IA and other mold infections in hematologic malignancy patients.     

Direct Susceptibility Testing with Positive BacT/Alert Blood Cultures by Using MicroScan Overnight and Rapid Panels

Studies were conducted on a method of direct inoculation of MicroScan dried overnight and of rapid panels with positive aerobic blood cultures obtained from the BacT/Alert to determine antimicrobial susceptibilities. Inocula were limited to specimens that appeared unimicrobic on Gram stain. Results were compared to those obtained from panels inoculated following subculture. For 133 gram-negative bacilli, there were 94.7 and 93.5% categorical agreements between direct and standard methods for all drugs tested with overnight and rapid panels, respectively. For 104 gram-positive cocci, there were 93.2 and 93.1% categorical agreements for overnight and rapid panels, respectively. The major error (false resistance) rate for gram negatives was 1.4% for overnight versus 0.7% for rapid panels. The very major error (false susceptibility) rate was 2.7% for overnight versus 8.1% for rapid panels. The total error rates were 1.6% for overnight panels and 1.5% for rapid panels. The major error rates for gram-positive direct susceptibility tests were 2.6% for overnight and 2.5% for rapid panels. The very major error rates were 8.8 and 7.2% for overnight and rapid panels, respectively. Total error rates were 3.6% for overnight and rapid gram-positive panels. These findings suggest that susceptibility results obtained from directly inoculated gram-negative overnight panels have the greatest correlation to those obtained by standard methods. When discrepant results occur with direct-susceptibility testing, they are more likely to show false susceptibility than false resistance.     

Evaluation of Rapid Prenatal Human Immunodeficiency Virus Testing in Rural Cameroon

Pregnant women (n = 859) in rural Cameroonian prenatal clinics were screened by two rapid human immunodeficiency virus (HIV) antibody tests (rapid tests [RT]) (Determine and Hema-Strip) using either whole blood or plasma. One additional RT (Capillus, HIV-CHEK, or Sero-Card) was used to resolve discordant results. RT results were compared with HIV-1 enzyme immunoassay (EIA) and Western blot (WB) results of matched dried blood spots (DBS) to assess the accuracy of HIV RTs. DBS EIA/WB identified 83 HIV antibody-reactive, 763 HIV antibody-nonreactive, and 13 indeterminate specimens. RT results were evaluated in serial (two consecutive tests) or parallel (two simultaneous tests) testing algorithms. A serial algorithm using Determine and Hema-Strip yielded sensitivity and specificity results of 97.6% and 99.7%, respectively, whereas a parallel RT algorithm using Determine plus a second RT produced a sensitivity and specificity of 100% and 99.7%, respectively. HIV RTs provide excellent alternatives for identifying HIV infection, and their field performance could be monitored using DBS testing strategies.     

Comparison of the Binax Legionella Urinary Antigen Enzyme Immunoassay (EIA) with the Biotest Legionella Urin Antigen EIA for Detection of Legionella Antigen in both Concentrated and Nonconcentrated Urine Samples

We evaluated a newly commercial enzyme immunoassay (EIA) (Biotest Legionella Urin Antigen EIA; Biotest AG, Dreieich, Germany) for detection of antigens of all Legionella pneumophila serogroups with a relatively wide spectrum of cross-reactivity as well as antigens of other Legionella spp. by comparing its sensitivity and specificity with those of an EIA for detection of L. pneumophila serogroup 1 antigen (Legionella urinary antigen EIA; Binax, Portland, Maine). Both tests were performed with both concentrated and nonconcentrated urine samples. We also evaluated the capabilities of both EIAs to detect extracted soluble antigens of American Type Culture Collection (ATCC) Legionella strains (L. pneumophila serogroups 1 to 14, L. bozemanii, and L. longbeachae). The sensitivity of the Biotest EIA was 66.66% in nonconcentrated urine and 86.66% in concentrated urine. The sensitivity of the Binax EIA was 63.76% and 88.88% in nonconcentrated and concentrated urine, respectively. The specificity was 100% in nonconcentrated and concentrated urine for both assays. The Binax EIA and Biotest EIA detected extracted soluble antigens of L. pneumophila serogroups 1 to 14 and L. bozemanii ATCC strains. The cross-reactions observed with the Binax EIA were probably due to common epitopes directly related to lipopolysaccharide. Further studies are required to determine the usefulness of the Binax EIA for detection of urinary antigens from Legionella species and serogroups other than L. pneumophila serogroup 1. The Biotest EIA proved to be as rapid, sensitive, and specific as the Binax EIA for the diagnosis of legionellosis. Concentration of antigen present in urine increased the sensitivities of both techniques with no reduction in specificity.     

Rapid Assay for Simultaneous Detection and Differentiation of Immunoglobulin G Antibodies to Human Immunodeficiency Virus Type 1 (HIV-1) Group M, HIV-1 Group O, and HIV-2

A rapid immunodiagnostic test that detects and discriminates human immunodeficiency virus (HIV) infections on the basis of viral type, HIV type 1 (HIV-1) group M, HIV-1 group O, or HIV-2, was developed. The rapid assay for the detection of HIV (HIV rapid assay) was designed as an instrument-free chromatographic immunoassay that detects immunoglobulin G (IgG) antibodies to HIV. To assess the performance of the HIV rapid assay, 470 HIV-positive plasma samples were tested by PCR and/or Western blotting to confirm the genotype of the infecting virus. These samples were infected with strains that represented a wide variety of HIV strains including HIV-1 group M (subtypes A through G), HIV-1 group O, and HIV-2 (subtypes A and B). The results showed that the HIV genotype identity established by the rapid assay reliably (469 of 470 samples) correlates with the HIV genotype identity established by PCR or Western blotting. A total of 879 plasma samples were tested for IgG to HIV by a licensed enzyme immunoassay (EIA) (470 HIV-positive samples and 409 HIV-negative samples). When they were tested by the rapid assay, 469 samples were positive and 410 were negative (99.88% agreement). Twelve seroconversion panels were tested by both the rapid assay and a licensed EIA. For nine panels identical results were obtained by the two assays. For the remaining three panels, the rapid assay was positive one bleed later in comparison to the bleed at which the EIA was positive. One hundred three urine samples, including 93 urine samples from HIV-seropositive individuals and 10 urine samples from seronegative individuals, were tested by the rapid assay. Ninety-one of the ninety-three urine samples from HIV-seropositive individuals were found to be positive by the rapid assay. There were no false-positive results (98.05% agreement). Virus in all urine samples tested were typed as HIV-1 group M. These results suggest that a rapid assay based on the detection of IgG specific for selected transmembrane HIV antigens provides a simple and reliable test that is capable of distinguishing HIV infections on the basis of viral type.     

Evaluation of a Rapid Immunochromatographic Test for Diagnosis of Dengue Virus Infection

A rapid (<7-min) immunochromatographic test for immunoglobulin M (IgM) and IgG antibodies to dengue viruses was evaluated by using hospital admission and discharge sera from 124 patients. The reference laboratory diagnosis was based on the results of virus isolation, hemagglutination-inhibition assay (HAI), and enzyme immunoassay (EIA). By the standard assays, patients experienced primary dengue virus infection (n = 30), secondary dengue virus infection (n = 48), Japanese encephalitis (JE) virus infection (n = 20), or no flavivirus infection (n = 26). The rapid test demonstrated 100% sensitivity in the diagnosis of dengue virus infection and was able to distinguish between primary and secondary dengue virus infections through the separate determinations of IgM and IgG. For all patients with primary dengue virus infection a positive test for IgM to dengue virus and a negative test for IgG to dengue virus were obtained, whereas for 46 of 48 patients (96%) with secondary dengue virus infection, a positive test for IgG to dengue virus with or without a positive test for IgM to dengue virus was obtained. The remaining two patients with secondary dengue virus infection had positive IgM test results and negative IgG test results. Furthermore, the rapid test was positive for patients confirmed to be infected with different dengue virus serotypes (12 infected with dengue virus serotype 1, 4 infected with dengue virus serotype 2, 3 infected with dengue virus serotype 3, and 2 infected with dengue virus serotype 4). The specificity of the test for nonflavivirus infections was 88% (3 of 26 positive), while for JE virus infections the specificity of the test was only 50% (10 of 20). However, most patients with secondary dengue virus infection were positive for both IgM and IgG antibodies to dengue virus, while no patients with JE virus infection had this profile, so cross-reactivity was only a concern for a small proportion of patients with secondary dengue infections. The rapid test demonstrated a good correlation with the reference EIA and HAI and should be useful for the rapid diagnosis of dengue virus infections.     

Evaluation of Pyloriset Screen, a Rapid Whole-Blood Diagnostic Test for Helicobacter pylori Infection

Helicobacter pylori infection can be detected by several invasive tests based on gastroscopy and by noninvasive methods such as serologic assays. Noninvasive tests can be used not only in addition to invasive tests but also by themselves to screen for H. pylori infection in patients who are not in urgent need of endoscopy. Lately, rapid qualitative serologic tests have been developed. In the present study, the accuracy of a novel rapid whole-blood test, Pyloriset Screen, detecting immunoglobulin G (IgG) and IgA antibodies against H. pylori was evaluated. A total of 207 consecutive adult outpatients referred for upper endoscopy were enrolled. Gastric biopsy specimens were taken from the antrum and corpus for histologic examination and rapid urease testing. Cultures were available for 113 patients. Serum samples collected from all patients were tested for H. pylori antibodies by two enzyme immunoassays (EIAs) (Pyloriset EIA and an in-house EIA), a rapid latex agglutination test (Pyloriset Dry), and Pyloriset Screen. Patients were considered H. pylori positive if helicobacters were seen on histologic examination (77 patients) or, if in combination with histologically verified (although helicobacter-negative) gastritis, their IgG antibody titers were elevated in the two EIAs (five patients). The Pyloriset Screen test had a sensitivity of 95%, a specificity of 94%, a positive predictive value of 91%, and a negative predictive value of 97%. Among 63 patients under the age of 45 years, the Pyloriset Screen test did not miss a single H. pylori diagnosis, and only 1 patient had a false-positive result. Pyloriset Screen could be used reliably to screen for H. pylori infection.     

Evaluation of the recombinant VlsE-based liaison chemiluminescence immunoassay for detection of Borrelia burgdorferi and diagnosis of Lyme disease

Recent efforts to improve the serologic diagnosis of Lyme disease have included the use of a synthetic peptide (C6) that reproduces the sequence of invariable region 6 of VlsE, the variable surface antigen of Borrelia burgdorferi. In the present study, the diagnostic performance of DiaSorin's recombinant VlsE-based chemiluminescence immunoassay in 1,947 human serum samples was evaluated. Sensitivity was determined using two serum panels from the CDC. For panel I, we observed sensitivities of 68.4% and 75.6% for subjects with early, localized (n = 19) or disseminated (n = 41) disease, respectively. For panel II, we observed sensitivities of 61.5% and 100% for subjects with early (n = 26) or late-stage (n = 11) disease, respectively. We observed a specificity of 99.5% for healthy donors (n = 600) living either in regions of the United States where the disease is endemic or in regions where it is not endemic. Overall, specificity among 207 potentially cross-reactive sera from subjects who had other spirochetal infections, nonspirochetal infections including bacterial and viral infections, or autoimmune or neurologic disease; who were positive for rheumatoid factor or anti-mouse antibodies; or who had been previously vaccinated for Lyme disease was 93.7%. In a direct comparison of 1,038 prospectively collected samples for Lyme disease testing we observed a relative sensitivity of 70%, a relative specificity of 99.1%, and an overall agreement of 97.1% between the DiaSorin recombinant VlsE chemiluminescence immunoassay and the Immunetics peptide-based C6 enzyme-linked immunosorbent assay.     

Use of Molecular and Reference Susceptibility Testing Methods in a Multicenter Evaluation of MicroScan Dried Overnight Gram-Positive MIC Panels for Detection of Vancomycin and High-Level Aminoglycoside Resistances in Enterococci

Modified MicroScan gram-positive MIC no. 8 panels (PM-8) were analyzed for their improved ability to detect vancomycin resistance (VR) and high-level aminoglycoside resistance (HLAR) in enterococci. A validation study design that utilized selected challenge strains, recent clinical isolates, and reproducibility experiments in a multicenter format was selected. Three independent medical centers compared the commercial panels to reference broth microdilution panels (RBM) and Synergy Quad Agar (QA). Resistance was verified by demonstration of VR and HLAR genes by PCR tests. The study was conducted in three phases. (i) In the challenge phase (CP), two well-characterized sets of enterococci were obtained from the Centers for Disease Control and Prevention; one set contained 50 isolates for VR testing and one contained 48 isolates for HLAR testing. In addition, a set of 47 well-characterized isolates representing diverse geographic areas, obtained from earlier national surveillance studies, was tested at the University of Iowa College of Medicine (UICM). (ii) In the efficacy phase (EP), each laboratory tested 50 recent, unique clinical isolates by all methods. (iii) In the reproducibility Phase (RP), each laboratory tested the same 10 strains by all methods in triplicate on three separate days. All isolates from the EP were sent to the UICM for molecular characterization of vanA, -B, -C₁, -C_2–3, and HLAR genes. In the CP, the ranking of test methods by error rates (in parentheses; very major and major errors combined, versus PCR results) were as follows: for high-level streptomycin resistance (HLSR), QA (12.0%) > PM-8 (5.2%) > RBM (1.6%); for high-level gentamicin resistance (HLGR), RBM (3.7%) > PM-8 (3.1%) > QA (2.6%); and for VR, RBM = QA (3.0%) > PM-8 (1.2%). In the EP, agreement between all methods and the reference PCR result was 98.0% for HLSR, 99.3% for HLGR, and 98.6% for VR. In the RP, the percentages of results ± 1 log₂ dilution of the all-participant mode were as follows: for VR, 100% (PM-8), 98.9% (QA), and 90.0% (RBM); for HLSR, 99.6% (RBM), 98.5% (PM-8), and 82.2% (QA); and for HLGR, 99.6% (RBM), 99.3% (PM-8), and 98.1% (QA). The ability of the PM-8 to detect VR and HLAR in enterococci was comparable to those for reference susceptibility and molecular PCR methods and was considered acceptable for routine clinical laboratory use.     

Usefulness of Leifson Staining Method in Diagnosis of Helicobacter pylori Infection

The Leifson staining method was used to diagnose Helicobacter pylori infection and was compared to histology, culture, and the rapid urease test (RUT). Histology gave the best sensitivity (98%), compared to Leifson staining (97%), culture (92%), and RUT (85%) (P < 0.005). Leifson staining is a sensitive, rapid, economical method for diagnosis of H. pylori infection in dyspeptic patients.     

Utility of real-time PCR for diagnosis of Legionnaires' disease in routine clinical practice

The main aim of our study was to determine the added value of PCR for the diagnosis of Legionnaires’ disease (LD) in routine clinical practice. The specimens were samples submitted for routine diagnosis of pneumonia from December 2002 to November 2005. Patients were evaluated if, in addition to PCR, the results of at least one of the following diagnostic tests were available: (i) culture for Legionella spp. on buffered charcoal yeast extract agar or (ii) detection of Legionella pneumophila antigen in urine specimens. Of the 151 evaluated patients, 37 (25%) fulfilled the European Working Group on Legionella Infections criteria for a confirmed case of LD (the “gold standard”). An estimated sensitivity, specificity, and overall percent agreement of 86% (32 of 37; 95% confidence interval [CI] = 72 to 95%), 95% (107 of 112; 95% CI = 90 to 98%), and 93% (139 of 149), respectively, were found for 16S rRNA-based PCR, and corresponding values of 92% (34 of 37; 95% CI = 78 to 98%), 98% (110 of 112; 95% CI = 93 to 100%), and 97% (144 of 149), respectively, were found for the mip gene-based PCR. A total of 35 patients were diagnosed by using the urinary antigen test, and 34 were diagnosed by the 16S rRNA-based PCR. With the mip gene PCR one more case of LD (n = 36; not significant) was detected. By combining urinary antigen test and the mip gene PCR, LD was diagnosed in an additional 4 (11%) patients versus the use of the urinary antigen test alone. The addition of a L. pneumophila-specific mip gene PCR to a urinary antigen test is useful in patients with suspected LD who produce sputum and might allow the early detection of a significant number of additional patients.     

Multicenter Evaluation of the Amplicor Enterovirus PCR Test with Cerebrospinal Fluid from Patients with Aseptic Meningitis

The Amplicor Enterovirus PCR test was compared with viral culture for the detection of enteroviruses in cerebrospinal fluid (CSF) specimens. In a multicenter study in which nine laboratories participated, a total of 476 CSF specimens were collected from patients with suspected aseptic meningitis. Sixty-eight samples were positive by PCR (14.4%), whereas 49 samples were positive by culture (10.4%), demonstrating that the Amplicor Enterovirus PCR test was significantly more sensitive than culture (P < 0.001). After discrepancy analysis the sensitivity and specificity of the Amplicor Enterovirus PCR test obtained by using viral culture as the “gold standard” were 85.7 and 93.9%, respectively. Our results with the CSF specimens collected in different countries demonstrate that the Amplicor test is capable of detecting a large variety of enterovirus serotypes and epidemiologically unrelated isolates in CSF specimens from patients with aseptic meningitis. The Amplicor Enterovirus PCR test is a rapid assay which can be routinely performed with CSF samples and is an important improvement for the rapid diagnosis of enteroviral meningitis.     

Evaluation of a New Competitive Immunoassay (BioElisa Syphilis) for Screening for Treponema pallidum Antibodies at Various Stages of Syphilis

The BioElisa Syphilis, a new competitive enzyme immunoassay (EIA) for Treponema pallidum whole antigen that uses specific human immunoglobulin G (IgG) antibodies as the competitor, was evaluated for potential use in screening for syphilis at various stages. The results obtained by this competitive EIA were compared with those obtained by the fluorescent treponemal antibody absorption (FTA-abs) test and the T. pallidum hemagglutination assay (TPHA). Serum samples from 434 patients with positive TPHA and FTA-abs test results, including patients with primary, latent, secondary, and tertiary syphilis and neurosyphilis, were investigated. Two samples tested negative by competitive EIA but were weakly reactive by the TPHA and the FTA-abs test. Sixteen serum samples from patients with clinically documented active syphilis, including several patients infected with human immunodeficiency virus, tested positive by the competitive EIA. There was a direct inverse correlation between EIA indices and titers in the TPHA and the FTA-abs test for all samples that tested positive. Specificity was assessed by testing 358 serum samples which tested negative for syphilis by TPHA and the FTA-abs test, including 100 serum samples from patients with documented infectious or autoimmune diseases. Only two serum samples gave a weakly positive EIA result. Thus, competitive EIA had a sensitivity of 99.5% and a specificity of 99.4% relative to the results of the FTA-abs test and TPHA. Our evaluation shows that BioElisa Syphilis is a sensitive, specific, and simple assay for screening for syphilis.     

Validation of a Modified Commercial Enzyme-Linked Immunoassay for Detection of Human Immunodeficiency Virus Type 1 Immunoglobulin G Antibodies in Saliva

This study was performed to evaluate the performance of a saliva collection device (OmniSal) and an enzyme-linked immunoassay (EIA) designed for use on serum samples (Detect HIV1/2) to detect human immunodeficiency virus type 1 (HIV-1) antibodies in the saliva of high-risk women in Mombasa, Kenya. The results of the saliva assay were compared to a “gold standard” of a double-EIA testing algorithm performed on serum. Individuals were considered HIV-1 seropositive if their serum tested positive for antibodies to HIV-1 by two different EIAs. The commercial serum-based EIA was modified to test the saliva samples by altering the dilution and lowering the cutoff point of the assay. Using the saliva sample, the EIA correctly identified 102 of the 103 seropositive individuals, yielding a sensitivity of 99% (95% confidence interval [CI], 94 to 100%), and 96 of the 96 seronegative individuals, yielding a specificity of 100% (95% CI, 95 to 100%). In this high-risk population, the positive predictive value of the assay was 100% and the negative predictive value was 99%. We conclude that HIV-1 antibody testing of saliva samples collected with this device and tested by this EIA is of sufficient sensitivity and specificity to make this protocol useful in epidemiological studies.