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Herd sensitivity in relation to test sensitivity in swine vesicular disease serological tests.

After the swine vesicular disease (SVD) outbreaks in 1992 in the Netherlands a national monitoring programme was initiated, testing 12 samples from every pig farm three times per year. In this monitoring a slightly higher cut-off was used than the cut-off agreed on within the European community. The author has analysed the effect of this higher cut-off on the percentage of false positive and false negative results, using information on SVD antibody titres in sera obtained from the monitoring programme and the outbreaks in 1992 and 1994. The number of false positive results was reduced by 63% when using the higher cut-off. On average the test sensitivity was reduced from 100% to 88%, resulting in a change of the average herd sensitivity from 91.7% to 91.5%, when testing 12 samples per farm. When three samples per farm were tested, the average herd sensitivity changed from 64.9% to 62.9%. The results further indicate that, in contrast to what is generally presumed, there is a relationship between test sensitivity and the prevalence of infection. The results clearly show that sample size is far more important in obtaining a high herd sensitivity than achieving a high test sensitivity.

Animals↗

The diagnostic efficiency of some serological tests for bovine brucellosis.

Results obtained from 1887 sera using three serological tests for bovine brucellosis were compared with a serological classification of sera described as the 'probable infection status'. Sera showing apparent false positive and apparent false negative reactions were identified, and were subjected to supplementary testing as appropriate. The serum agglutination test (SAT) gave 35% apparent false negative reactions and 5% apparent false positives. The complement fixation test (CFT) gave 12% apparent false negative reactions using warm fixation (CFTW) and at least 5% using cold fixation (CFTC). The routine diagnostic system used in Victoria, in which the CFTW is supplemented by the CFTC and the SAT, gave 9% apparent false negative reactions and 2% apparent false positive reactions. The radioimmunoassay gave 1% or 6% apparent false negative reactions, depending on the minimum diagnostic value used. Atypical reactions in the CFT sometimes caused difficulties in diagnosis.

Agglutination Tests↗

Performance of indirect immunoglobulin M (IgM) serology tests and IgM capture assays for laboratory diagnosis of measles.

As progress is made toward elimination of measles, the laboratory confirmation of measles becomes increasingly important. However, both false-positive and false-negative results can occur with the routinely used indirect measles immunoglobulin M (IgM) serology tests. The measles IgM capture assay is considered to be more specific, and therefore, its use is indicated for confirmatory testing, but its relative performance has not been fully assessed. Four commercial indirect measles IgM serology test kits (the Behring, Clark, Gull, and PanBio assays) and a commercial IgM capture assay (the Light Diagnostics assay) were evaluated for their abilities to detect measles virus-specific IgM antibody with a total of 308 serum samples from patients involved in a measles outbreak and with confirmed cases of measles and 454 samples from subjects without measles. The Centers for Disease Control and Prevention (CDC) IgM capture assay was also used in a part of the evaluation. Among the indirect assays, the overall sensitivities ranged from 82.8% (Clark assay) to 88.6% (Behring assay) and specificity ranged from 86.6% (PanBio assay) to 99.6% (Gull assay). These rates were 92.2 and 86. 6%, respectively, for the Light Diagnostics capture assay and 87.0 and 94.8%, respectively, for the CDC capture assay. While the Light Diagnostics capture assay had the best detection rate (80%) with the acute-phase samples compared with those for the rest of the tests (CDC capture assay, 77%; Behring assay, 70%; Gull assay, 69%; PanBio assay, 58%; and Clark assay, 57%), all tests showed a significantly improved sensitivity in the range of 92% (Clark and PanBio assays) to 97% (Light Diagnostics and CDC capture assays) with the convalescent-phase samples, as expected. The best seropositivity rates (in the range of 92 to 100%) were observed with samples collected 6 to 14 days after the onset of symptoms. The Gull assay showed the highest positive predictive value (99.6%), followed by the Behring assay (97.8%) and the CDC capture assay (96.1%). Overall, the Gull and Behring assays were found to be as good as or better than the capture assays. In conclusion, laboratory diagnosis of measles based on IgM serology varies depending on the timing of specimen collection and the test used, and the case for the use of the IgM capture assay as the confirmatory test appears to be uncertain.

Antibodies, Viral↗

Serological testing for campylobacteriosis with sera forwarded for Salmonella and Yersinia serology.

Single serum specimens forwarded for Salmonella and Yersinia serology, from a total of 250 patients, were tested for anti-C. jejuni antibodies of the IgG class. Anti-Salmonella and anti-Y. enterocolitica O3 antibodies were examined by a microagglutination test and anti-C. jejuni antibodies by ELISA against a C. jejuni ultrasonicate before (ELISA) and after neutralization of antibodies which cross-reacted with Helicobacter pylori antigens (ELISA-Abs). Blood donor sera (n = 50) and sera (n = 40) from patients with various infectious diseases served as controls. A positive test for anti-Salmonella antibodies was recorded in 4/250 (1.6%) of the patients, for anti-Yersinia antibodies in 7/250 (2.8%), and for anti-C. jejuni antibodies in 7/250 (2.8%) in the ELISA; in 25/250 (10%) in the ELISA-Abs. No mixed infection was recorded by the serological testing. The ELISA-Abs showed a diagnostic specificity of 97.7%. Our results support the inference that diagnostic serology for enteropathogenic bacteria should include serology for C. jejuni, preferably by tests which exclude participation by antibodies which cross-react with H. pylori antigens.

Antibodies, Bacterial↗

Detection of Helicobacter pylori antibodies in a pediatric population: comparison of three commercially available serological tests and one in-house enzyme immunoassay.

A serum immunoglobulin G enzyme immunoassay (EIA) for Helicobacter pylori antibodies already in use in adults was evaluated with 99 pediatric serum samples to determine its usefulness for the study of H. pylori disease in children. The reference method used was either the (13)C-urea breath test or a biopsy culture of gastric mucosa. In children, an EIA cutoff of 0.35 absorbancy unit yielded sensitivity, specificity, and positive and negative predictive values of 93, 97, 93, and 97%, respectively. The cutoff recommended when this EIA was published for use in adults was 0.70 absorbancy unit (H. Gnarpe, P. Unge, C. Blomqvist, and S. Mäkitalo, APMIS 96:128-132, 1988). Another subset of 169 serum samples taken from children was analyzed by four serological tests in order to compare the performance of the in-house EIA with the Pyloriset, HM-CAP, and Helico-G kits. For the 169 samples, 10 (5.9%) false-positives and no false-negatives occurred with the Helico-G, 3 (1.8%) false-positives and no false-negatives occurred with the Pyloriset, and 3 (1.8%) false-positives and 1 (0.6%) false-negative occurred with the HM-CAP. For the 169 samples, 1 (0.6%) false-positive and no false-negatives occurred with the in-house EIA. Serological detection of H. pylori antibodies with our EIA seems to be valuable in diagnosing H. pylori infection in children, but only if a lowered, specific pediatric cutoff is established. The commercial kits, particularly the Helico-G, seem to overdiagnose pediatric H. pylori infection. A positive serological test for H. pylori infection, particularly for children, needs to be confirmed by a reference method because of the possibility of spontaneous eradication of infection, with a lingering serological response.

Adolescent↗

Comparative sensitivity of different serological tests for seromonitoring and surveillance of Edwardsiella tarda infection of Indian major carps.

Different serological tests viz. indirect ELISA, indirect blocking ELISA, competitive ELISA and serum agglutination tests were evaluated to detect antibodies against Edwardsiella tarda in naturally infected fish sera for seromonitoring and epizootiological studies. Approximately 66.6, 62.5, 57.6 and 16.6% of the field sera samples were found to be positive by indirect ELISA, competitive ELISA, indirect blocking ELISA and serum agglutination test, respectively. The percentage of serum samples positive for E. tarda antibodies in serum agglutination, competitive ELISA and indirect blocking ELISA, when compared with indirect ELISA, were 33.3, 83.6 and 66.6%, respectively, but its use was restricted due to the requirement of several conjugates against different fish species and the difficulty in assaying large numbers of serum samples from different fish species in a limited time to enable seromonitoring of the disease prevalence. No significant difference (P<0.05) in the mean optical density value was found in indirect and competitive ELISA. Although the competitive ELISA was slightly less sensitive than the indirect ELISA, it could accommodate a large number of serum samples with one anti-rabbit conjugate, and the need for different fish conjugates as required in indirect ELISA was eliminated. As in medical and veterinary practices, these tests can now be used in aquaculture practices for seromonitoring and study of pre-exposure of Indian major carps to pathogens in enzootic areas.

Animals↗

Toxoplasma lymphadenitis. Analysis of cytologic and histopathologic criteria and correlation with serologic tests.

OBJECTIVE: To identify cases of Toxoplasma lymphadenitis by light microscopic examination of fine needle aspiration cytology (FNAC) smears and paraffin sections and to correlate the result with those of serologic tests. STUDY DESIGN: The study group consisted of 19 cases of Toxoplasma lymphadenitis, 7 of which were diagnosed by FNAC, 9 on excision biopsy and 3 on FNAC followed by biopsy. Nineteen cases of reactive lymphadenitis, tuberculosis and infectious mononucleosus composed the control group. Sera from all 38 patients were screened for antibodies to Toxoplasma. RESULTS: Eleven of 19 cases (58%) of Toxoplasma adenitis had very high titers of antibody (> 300 ELISA units/ml), and 6 cases (31%) had antibody titers in a range suggestive of active infection (210-300 ELISA units/mL) and required demonstration of rising titers. Overall, 89% of patients with Toxoplasma lymphadenitis showed significant levels of antibody. All patients from the control group showed consistently low levels of antibody to Toxoplasma. CONCLUSION: Though serologic tests are mandatory for the diagnosis of Toxoplasma lymphadenitis, a high index of suspicion can be obtained by means of light microscopy alone.

Adolescent↗

Serologic testing for human immunodeficiency virus antibodies.

Familiarity with available serologic tests for antibodies to human immunodeficiency virus (HIV) has become increasingly important in a wide variety of clinical settings. Enzyme-linked immunosorbent assay (ELISA) commercial kits are most often used as Enzyme-linked immunosorbent assay (ELISA) commercial kits are most often used as screening tests, and Western blot techniques are used for confirmation of positive results. ELISA specificity and sensitivity exceed 98%; the predictive value of a positive test varies from 2% for a weakly positive test in a low-prevalence population to 99% for a strongly positive test in a high-risk group. Confirmatory Western blot testing identifies antibodies with affinity for specific HIV antigens. Indeterminate Western blot antibody patterns necessitate subsequent testing or alternative methods for interpretation. A "window" period of up to 3 or more months follows acute HIV infection before seropositivity occurs.

Antibodies, Viral↗

Psychological responses to serological testing for HIV.

To determine the emotional impact of serological testing for HIV, 218 physically asymptomatic adults were evaluated in a confidential clinical setting 2 weeks before HIV test notification, immediately before and after notification, and 2 and 10 weeks later. All received extensive pre- and post-test counseling. The 179 seronegatives reported one or more HIV risk behaviors: homosexual intercourse (n = 111), heterosexual intercourse with possibly infected partners (n = 62), intravenous drug use (n = 20). Immediately after notification, seronegatives had significant decreases in visual analogue scale (VAS) measures of anxiety, depression, fear of getting AIDS, and fear of having infected others. Reductions were sustained at both follow-up assessments and were complemented by significant reductions on standardized self-reported measures of anxiety (Spielberger State Anxiety Inventory, SAI), depression (Beck Depression Inventory, BDI), and psychiatric symptoms (Brief Symptom Inventory, BSI) as well as by clinical ratings of depression (Hamilton Depression Rating Scale, HDRS). Of 39 seropositives, 35 had homosexual risk behaviors, seven had been intravenous drug users (IVDUs; four of whom were homosexual men), and one was a female partner of an IVDU. Immediately after notification, VAS measures of their anxiety were not significantly increased, and at 10 weeks after notification, their VAS measures of distress and mean scores on BDI, SAI and BSI were significantly lower than at entry. Their HDRS ratings were not significantly increased.

AIDS Serodiagnosis↗

A comparison of antibodies to tissue transglutaminase with conventional serological tests in the diagnosis of coeliac disease.

BACKGROUND: Tissue transglutaminase is now recognized as the autoantigen for antiendomysial antibodies. Antibodies to tissue transglutaminase have been proposed as a valuable test for coeliac disease. OBJECTIVE: To determine the value of antibodies to tissue transglutaminase in the diagnosis of coeliac disease in our outpatient population. METHODS: Patients who underwent serological tests for coeliac disease during the first 18 months of the tissue transglutaminase antibody assay were retrospectively identified from the regional serology laboratory database. Patients' symptoms were noted, along with serological results and duodenal histology in those patients who underwent duodenal biopsy. RESULTS In total, 586 patients were identified as having been serologically tested for coeliac disease, of whom 92 patients (33 men; mean age 51.7 years) had been followed up with duodenal biopsies. Of these 92 patients, 29 (31%; 14 men; mean age 52.5 years) had histological features of coeliac disease. The 63 patients with normal histology (19 men; mean age 51.8 years) acted as controls. Weight loss was more frequent in coeliac disease patients compared to controls (7 vs 5; P = 0.04) whereas the frequency of anaemia (P = 0.85) and diarrhoea (P = 0.74) did not differ significantly between the two groups. The sensitivity and specificity of tissue transglutaminase antibodies (86%; 84%) were compared to those for antiendomysial antibodies (90%; 98%) and antigliadin antibodies (76%; 79%). CONCLUSIONS: The diagnostic value of tissue transglutaminase antibodies was intermediate between that of antiendomysial antibodies and antigliadin antibodies. However, duodenal biopsy remains the gold standard diagnostic test for coeliac disease.

Adult↗

Serologic testing of badgers to monitor plague in southwestern Idaho.

Serologic testing of badgers (Taxidea taxus) was used to monitor plague (Yersinia pestis) in a Townsend ground squirrel (Spermophilus townsendi) population in 10,000 ha of the Snake River Birds of Prey Study Area, Idaho. Eighty-six percent of the 294 sera tested in 1975 and in 1976 were positive. Significantly fewer (72%) seropositives occurred in 1977. Seasonal changes in the percentage of seropositives and the decline in 1977 were probably due to the phenology of the Townsend ground squirrel and the proportion of that species in the badger's diet. Eight Townsend ground squirrels found dead had positive bacteriologic tests for plague; however, a high mortality in the ground squirrel population was not observed. Food habits and movement patterns of badgers made them ideal for documenting the geographical and temporal characteristics of the plague focus.

Animals↗

[Results of serological tests for syphilis used in preventive examinations].

Results of serological tests for syphilis performed on donors and patients at the Institute of Haematology over the last two years are summarized. The results of tests performed by cardiolipins ++ USR and VDRL antigens, and later confirmed using FTA-ABS and TPHA methods were evaluated. They indicate that the recently produced USR antigen is more sensitive and more specific than VDRL antigen. Similarly, TPHA proves to be more sensitive than FTA-ABS test in these prophylactic assays.

Blood Donors↗

Evaluation of five serologic tests for antibody to Neisseria gonorrhoeae.

Sera from 1,167 individuals were tested for antibody to Neisseria gonorrhoeae by use of five different serologic tests. These were complement fixation, the indirect fluorescent antibody test, Gonosticon Dri-Dot, fluorescent gonorrhea test-heated, and gonorrhea screen test. Parallel cultures of material from the throat, urethra, cervix, and rectum were also done. The results were analyzed by a technique intended to separate test effects from population effects. Test specificities ranged from 81.3% for the Dri-Dot test to 96.1% for the indirect fluorescent antibody test. Sensitivities ranged from 55.6% for the Dri-Dot test to 81.5% for the fluorescent gonorrhea test-heated.

Adolescent↗

Seroreversion of the serological tests for syphilis in the newborns born to treated syphilitic mothers.

BACKGROUND: IgG antibodies from mothers adequately treated for syphilis can cross the placenta and appear in the sera of healthy newborns without infection. In such infants, a false diagnosis of congenital syphilis is often made. We have designed a retrospective survey to determine the time of seroreversion of the serological tests for syphilis (STS) in uninfected newborns born to mothers who were adequately treated for syphilis. MATERIALS AND METHODS: Fifty two seropositive, untreated newborns born to 51 mothers treated for syphilis were studied. The newborns were followed at 1, 3, 6, 9, and 12 months of age until seroreversion was detected. The VDRL test was followed until 12 months in 12 of the 22 newborns who were positive at birth, the TPHA in 21 of the 46 newborns, and the FTA-ABS test in 22 of the 48 newborns. RESULTS: In the first serological tests done within 1 month after birth, the VDRL was positive in 22 newborns (42%), the TPHA in 46 (88%), and FTA-ABS in 48 (92%). The VDRL seroreverted within 6 months after birth in 84%, and within 1 year in 100%. The TPHA test seroreverted in 95% within 1 year after birth. The FTA-ABS test seroreverted in 100% within 1 year after birth. CONCLUSIONS: In most seropositive, untreated newborns born to treated mothers the VDRL became negative within 6 months after birth and the TPHA and FTA-ABS within 1 year. This result is consistent with current Centers for Disease Control (CDC) guidelines. However, although the CDC guidelines are adequate in general, we think that some revision is desirable concerning the IgM test and combination of the test results in order to rule out congenital syphilis in seropositive, nonsymptomatic newborns born to the treated mothers.

Female↗

The significance of serologic test for EB-virus antibody in occult type nasopharyngeal carcinoma.

Since antibody titers against Epstein-Barr virus (EBV) antigens are often elevated in sera of patient with active undifferentiated and nonkeratinizing nasopharyngeal carcinoma, anti-EBV serologic tests have been applied for diagnosis of metastatic lymphadenopathy in the neck without an obvious source and/or suspicious tumor of the nasopharynx. In this study it is emphasized that the serologic test procedure was helpful in diagnosing a patient with nasopharyngeal carcinoma that was initially occult but eventually confirmed by biopsy.

Antibodies, Viral↗

Evaluation of four serological tests for bovine paratuberculosis.

The standard complement fixation (CF) test, a commercial agarose gel immunodiffusion (AGID) test (ImmuCell Corporation, Portland, Maine), and two commercial enzyme-linked immunosorbent assays (ELISAs; Allied Laboratories, Glenwood Springs, Colo. [Allied ELISA], and the CSL, Limited, [Parkville, Victoria, Australia] enzyme immunoassay [CSL ELISA]) were evaluated by using sera from the Repository for Paratuberculosis Specimens. The case definition of subclinical bovine paratuberculosis was isolation of Mycobacterium paratuberculosis from fecal samples or internal organs of dairy cattle without diarrhea or weight loss. Animals designated as free of the disease originated exclusively from certified paratuberculosis-free herds in Wisconsin. None of the cattle evaluated had been vaccinated for paratuberculosis. Among 177 M. paratuberculosis-infected cattle, the CF test, the AGID test, the Allied ELISA, and the CSL ELISA had test sensitivities of 38.4, 26.6, 58.8, and 43.4%, respectively, and specificities of 99.0, 100.0, 95.4, and 99.0%, respectively. Only 108 of the infected cattle were confirmed by culture or by a commercial DNA probe (IDEXX Corporation, Portland, Maine) to be shedding the organism in fecal samples at the time of serological testing. Among the 108 M. paratuberculosis fecal shedders, the CF test, the AGID test, the Allied ELISA, and the CSL ELISA were positive for 54.6, 40.7, 65.7, and 56.5% of the cows, respectively; and among the 69 cows that were nonshedders, the tests were positive for 14.5, 4.3, 47.8, and 24.6% of the cows, respectively. There was a significant difference (P < 0.05) in the rate of positive test results for all four tests between these two groups of animals. The CF test performed well when it was compared with the other serological tests if a titer of >/- 1.8 was classified as a positive test result.

Animals↗