scholarly journals Bicentric Evaluation of Six Anti-Toxoplasma Immunoglobulin G (IgG) Automated Immunoassays and Comparison to the Toxo II IgG Western Blot

2009 ◽  
Vol 16 (9) ◽  
pp. 1322-1326 ◽  
Author(s):  
Arnaud Maudry ◽  
Gautier Chene ◽  
Rémi Chatelain ◽  
Hugues Patural ◽  
Bahrie Bellete ◽  
...  
Keyword(s):  
Western Blot ◽  
False Positive ◽  
Relative Sensitivity ◽  
Pharmaceutical Companies ◽  
Serum Samples ◽  
Serological Status ◽  
Roche Diagnostics ◽  
Positive Results ◽  
Very High ◽  
Imperfect Sensitivity

ABSTRACT A comparative study of the Toxoplasma IgGI and IgGII Access (Access I and II, respectively; Beckman Coulter Inc.), AxSYM Toxo IgG (AxSYM; Abbott Diagnostics), Vidas Toxo IgG (Vidas; bioMerieux, Marcy l'Etoile, France), Immulite Toxo IgG (Immulite; Siemens Healthcare Diagnostics Inc.), and Modular Toxo IgG (Modular; Roche Diagnostics, Basel, Switzerland) tests was done with 406 consecutive serum samples. The Toxo II IgG Western blot (LDBio, Lyon, France) was used as a reference technique in the case of intertechnique discordance. Of the 406 serum samples tested, the results for 35 were discordant by the different techniques. Using the 175 serum samples with positive results, we evaluated the standardization of the titrations obtained (in IU/ml); the medians (second quartiles) obtained were 9.1 IU/ml for the AxSYM test, 21 IU/ml for the Access I test, 25.7 IU/ml for the Access II test, 32 IU/ml for the Vidas test, 34.6 IU/ml for the Immulite test, and 248 IU/ml for the Modular test. For all the immunoassays tested, the following relative sensitivity and specificity values were found: 89.7 to 100% for the Access II test, 89.7 to 99.6% for the Immulite test, 90.2 to 99.6% for the AxSYM test, 91.4 to 99.6% for the Vidas test, 94.8 to 99.6% for the Access I test, and 98.3 to 98.7% for the Modular test. Among the 406 serum samples, we did not find any false-positive values by two different tests for the same serum sample. Except for the Modular test, which prioritized sensitivity, it appears that the positive cutoff values suggested by the pharmaceutical companies are very high (either for economical or for safety reasons). This led to imperfect sensitivity, a large number of unnecessary serological follow-ups of pregnant women, and difficulty in determining the serological status of immunosuppressed individuals.

scholarly journals Quantitative Approach for the Serodiagnosis of Canine Lyme Disease by the Immunoblot Procedure

2000 ◽  
Vol 38 (7) ◽  
pp. 2628-2632 ◽  
Author(s):  
Marta A. Guerra ◽  
Edward D. Walker ◽  
Uriel Kitron
Keyword(s):  
Logistic Regression ◽  
Lyme Disease ◽  
Natural Infection ◽  
Enzyme Linked Immunosorbent Assay ◽  
Serum Samples ◽  
Immunoblot Assay ◽  
Serological Status ◽  
Low Probability ◽  
Positive Results ◽  
Logistic Regression Equation

Serum samples obtained from healthy, asymptomatic dogs in areas of Wisconsin and northern Illinois where Lyme disease is endemic or nonendemic were assayed for antibodies to Borrelia burgdorferi by enzyme-linked immunosorbent assay (ELISA), and positive results were confirmed by immunoblot assay. We found that 56.9% (562 of 1,077) of the samples were positive by ELISA and 82.0% (461 of 562) were positive by immunoblotting. A logistic regression model was developed to distinguish between nonvaccinated dogs naturally infected with B. burgdorferi from areas where the disease is endemic and dogs from areas where the disease is nonendemic that were vaccinated against Lyme disease. Of the 18 protein bands analyzed, 8 were found to be significantly different (P < 0.05) between the two groups. p93, p34, p31, and p28 occurred with increased frequency in vaccinated dogs, while p58, p37, p35, and p30 occurred more frequently in naturally infected dogs. The logistic regression equation obtained was used to determine the probability of natural infection among vaccinated dogs residing in areas where the disease is endemic. Of 125 samples, 87.2% had a very low probability of natural infection and only 2.4% were highly likely to be infected. Logistic regression is a useful method for distinguishing between vaccinated and naturally infected dogs and predicting the serological status of vaccinated dogs from areas where Lyme disease is endemic.

Four rapid serum-urine combination assays of choriogonadotropin (hCG) compared and assessed for their utility in quantitative determinations of hCG

1994 ◽  
Vol 40 (10) ◽  
pp. 1944-1949 ◽  
Author(s):  
S H Mishalani ◽  
J Seliktar ◽  
G D Braunstein
Keyword(s):  
False Positive ◽  
The Other ◽  
Urine Samples ◽  
Serum Samples ◽  
Positive Urine ◽  
Sample Application ◽  
Positive Results ◽  
Hcg Test ◽  
In Pregnancy

Abstract We evaluated the performance of four visually read pregnancy tests (TestPack Plus hCG Combo, ICON II hCG, SureCell hCG-Serum/Urine and PregnaGen 1-Step) designed to detect increased concentrations of choriogonadotropin (hCG) in either serum or urine samples. The biochemical sensitivities and specificity in both serum and urine samples were similar for each kit. All kits correctly identified pregnancy serum samples: The TestPack Plus hCG Combo and SureCell hCG-Serum/Urine were 100% specific; the other two kits exhibited a few false-positive results. For urine samples the ICON II hCG test was 100% sensitive, and the other three were 99.5% sensitive, with false-positive urine results occasionally reported by the PregnaGen 1-Step and ICON II hCG tests. Quantitative hCG concentrations could be estimated in pregnancy serum samples, but not urine samples, through determination of the time elapsed from the sample application or addition of the final reagent to the first appearance of a positive result.

scholarly journals ‘False positive’ complement fixation with psittacosis—trachoma antigens due to antibodies in complement preparations

1964 ◽  
Vol 62 (2) ◽  
pp. 179-184 ◽  
Author(s):  
Alexander L. Terzin
Keyword(s):  
Guinea Pig ◽  
False Positive ◽  
Guinea Pigs ◽  
Technical Assistance ◽  
Complement Fixation ◽  
Experimental Studies ◽  
Serum Samples ◽  
Positive Serum ◽  
Set Up ◽  
Positive Results

Complement-fixation tests with psittacosis-trachoma group antigens, if set up with complement prepared from guinea-pigs cross-infected with any of the Bedsonia agents, may give completely false positive results. The use of C.F. positive or C.F. inhibition positive samples of guinea-pig sera as a source of complement can induce also a significant increase or decrease, respectively, of the actual C.F. titres in Bedsonia-positive serum samples tested. Observations made both in routine serology and in experimental studies show the necessity of testing carefully, for possible presence of Bedsonia titres, individual sera of guinea-pigs intended for use as source of complement in C.F. tests performed with Bedsonia group antigens.I have pleasure in thanking Dr F. B. Gordon and Dr E. Weiss for the valuable suggestions made and HM3 C.O. Wiese for the technical assistance.

Diagnostic pitfall of carryover: in automatic urine analyzers

2016 ◽  
Vol 41 (6) ◽  
Author(s):  
Eren Vurgun ◽  
Osman Evliyaoğlu ◽  
Sembol Yıldırmak ◽  
İbrahim Akarsubaşı
Keyword(s):  
Red Blood Cells ◽  
Microscopic Examination ◽  
False Positive ◽  
Blood Cells ◽  
Gross Hematuria ◽  
Urine Sediment ◽  
Carryover Effect ◽  
Diagnostic Pitfall ◽  
Positive Results ◽  
Very High

AbstractObjective:We aimed to find out whether there is significant carryover effect which causes false-positive hematuria on red blood cells (RBCs) in automatic urine chemistry (DIRUI H-800) and sediment (DIRUI FUS-200) analyzers.Methods:Twenty-four samples with gross hematuria selected as containing high RBC concentration and forty-eight samples which had both negative result in dipstick and 0/hpf in microscopic examination selected as containing low RBC concentration. Carryover% was calculated via the formula [carryover%=100×(bResults:Carryover% was very high (67%) in urine chemistry analyzer. Carryover% of urine sediment analyzer was found 0.4% whilst false-positive hematuria percentage was 87.5% for the first samples came after gross hematuria and 6.6% for the second samples. The first samples analyzed after gross hematuria had significantly higher (p<0.001) results than the second samples in both analyzers.Conclusion:In urine sediment analyzer, carryover% calculated by formula was found analytically sufficient, but it causes highly false-positive results due to diagnostic limit of hematuria (RBC>3/hpf) is low. To prevent carryover in both urine analyzers; washing procedures should be revised and the diagnostic effect of carryover should also be taken into account by biochemists.

scholarly journals Dengue antibodies can cross-react with SARS-CoV-2 and vice versa-Antibody detection kits can give false-positive results for both viruses in regions where both COVID-19 and Dengue co-exist

2020 ◽  
Author(s):  
Himadri Nath ◽  
Abinash Mallick ◽  
Subrata Roy ◽  
Soumi Sukla ◽  
Keya Basu ◽  
...  
Keyword(s):  
False Positive ◽  
Virus Antigen ◽  
Definitive Diagnosis ◽  
Antibody Detection ◽  
Serum Samples ◽  
Positive Serum ◽  
Antigen Tests ◽  
Positive Results

AbstractFive of thirteen Dengue antibody-positive serum samples, dated 2017 (pre-dating the COVID-19 outbreak) produced false-positive results in SARS-CoV-2 IgG/IgM rapid strip tests. Our results emphasize the importance of NAT and/or virus antigen tests to complement sero-surveillance for definitive diagnosis of COVID-19/Dengue in regions where both viruses are co-endemic.

scholarly journals Archived dengue serum samples produced false-positive results in SARS-CoV-2 lateral flow-based rapid antibody tests

2021 ◽  
Vol 70 (6) ◽  
Author(s):  
Himadri Nath ◽  
Abinash Mallick ◽  
Subrata Roy ◽  
Soumi Sukla ◽  
Keya Basu ◽  
...  
Keyword(s):  
Dengue Virus ◽  
False Positive ◽  
Lateral Flow ◽  
Accurate Estimation ◽  
Serum Samples ◽  
Positive Serum ◽  
Rapid Tests ◽  
Antibody Tests ◽  
Positive Results ◽  
Rapid Antibody

Co-endemicity of SARS-CoV-2 and dengue virus (DV) infection is becoming a matter of serious concern as it has been already reported that antibodies (Ab) elicited by SARS-CoV-2 infection can produce false-positive results in dengue IgG and IgM rapid tests and vice versa. Here we communicate that five of thirteen DV antibody-positive serum samples from Kolkata, archived in 2017 (predating the COVID-19 outbreak), produced false-positive results in SARS-CoV-2 IgG/IgM lateral flow-based rapid tests. Our results emphasize the importance of implementing tests with higher specificity to conduct sero-surveillance for accurate estimation of SARS-CoV-2/DV prevalence in regions where both viruses now co-exist.

Removal of thymoglobulin from post-renal transplant serum samples eliminates false positive results by flow cytometry crossmatch

2002 ◽  
Vol 63 (10) ◽  
pp. S102
Author(s):  
Jeremy Goodman ◽  
Martin D Jendrisak ◽  
Surendra Shenoy ◽  
Jeffrey A Lowell ◽  
T Mohanakumar
Keyword(s):  
Flow Cytometry ◽  
Renal Transplant ◽  
False Positive ◽  
Serum Samples ◽  
Positive Results

scholarly journals Evaluation of Serum Cryptococcal Antigen Testing Using Two Novel Semiquantitative Lateral Flow Assays in Persons with Cryptococcal Antigenemia

2020 ◽  
Vol 58 (4) ◽  
Author(s):  
Caleb Skipper ◽  
Kiiza Tadeo ◽  
Emily Martyn ◽  
Elizabeth Nalintya ◽  
Radha Rajasingham ◽  
...  
Keyword(s):  
False Positive ◽  
Diagnostic Performance ◽  
False Negative ◽  
Lateral Flow ◽  
Reference Standard ◽  
Serum Samples ◽  
Cryptococcal Antigen ◽  
Negative Results ◽  
Lateral Flow Assays ◽  
Positive Results

ABSTRACT Early cryptococcal disease can be detected via circulating antigen in blood before fulminant meningitis develops, when early antifungal therapy improves survival. Two semiquantitative cryptococcal antigen (CrAg) lateral flow assays (LFAs) have been developed, but their diagnostic performance has not been defined. Cryopreserved serum samples from HIV-infected Ugandans obtained as part of a prospective CrAg-screening cohort were tested in duplicate for CrAg by the CrAgSQ (IMMY) and CryptoPS (Biosynex) lateral flow assays. Case-controlled diagnostic performance was measured using the FDA-approved CrAg LFA (IMMY) as a reference standard via McNemar’s test. Of 99 serum samples tested, 57 were CrAg positive (CrAg+) by the CrAg LFA reference standard. By CrAgSQ, 57 were read as positive, with 98% sensitivity (56/57; 95% confidence interval [CI], 0.91 to 0.99) and 98% specificity (41/42; 95% CI, 0.88 to 0.99) (McNemar’s, P = 0.99). The sample with a false-negative result by CrAgSQ (n = 1) had a titer of <1:5, while the sample with a false-positive result (n = 1) yielded a 1+ result. By CryptoPS, 52 samples were read as positive, with 88% sensitivity (50/57; 95% CI, 0.76 to 0.95) and 95% specificity (40/42; 95% CI, 0.84 to 0.99) (McNemar’s, P = 0.18). The CryptoPS false-negative results included samples with titers of <1:5 (n = 1), 1:5 (n = 5), and 1:20 (n = 1), while samples with false-positive results by CryptoPS (n = 2) yielded Positive results. The CryptoPS assay missed 35% (7/20) of samples with CrAg LFA titers of ≤1:20. The new semiquantitative CrAg LFAs allow rapid estimation of titer levels in easy-to-perform platforms. The CrAgSQ demonstrated better qualitative sensitivity and specificity than the CryptoPS compared to the reference standard. The exact grading of the CrAgSQ results has some subjectivity, with interreader variability; however, qualitative reads were generally concordant for both assays.

scholarly journals False-Positive Results in a Recombinant Severe Acute Respiratory Syndrome-Associated Coronavirus (SARS-CoV) Nucleocapsid-Based Western Blot Assay Were Rectified by the Use of Two Subunits (S1 and S2) of Spike for Detection of Antibody to SARS-CoV

2006 ◽  
Vol 13 (3) ◽  
pp. 409-414 ◽  
Author(s):  
Mimoun Maache ◽  
Florence Komurian-Pradel ◽  
Alain Rajoharison ◽  
Magali Perret ◽  
Jean-Luc Berland ◽  
...  
Keyword(s):  
Severe Acute Respiratory Syndrome ◽  
Western Blot ◽  
False Positive ◽  
High Sensitivity ◽  
Cross Reactivity ◽  
Serum Samples ◽  
Western Blot Assay ◽  
N Protein ◽  
False Positive Diagnosis ◽  
Healthy Donors

ABSTRACT To evaluate the reactivity of the recombinant proteins expressed in Escherichia coli strain BL21(DE3), a Western blot assay was performed by using a panel of 78 serum samples obtained, respectively, from convalescent-phase patients infected with severe acute respiratory syndrome-associated coronavirus (SARS-CoV) (30 samples) and from healthy donors (48 samples). As antigen for detection of SARS-CoV, the nucleocapsid protein (N) showed high sensitivity and strong reactivity with all samples from SARS-CoV patients and cross-reacted with all serum samples from healthy subjects, with either those obtained from China (10 samples) or those obtained from France (38 serum samples), giving then a significant rate of false positives. Specifically, our data indicated that the two subunits, S1 (residues 14 to 760) and S2 (residues 761 to 1190), resulted from the divided spike reacted with all samples from SARS-CoV patients and without any cross-reactivity with any of the healthy serum samples. Consequently, these data revealed the nonspecific nature of N protein in serodiagnosis of SARS-CoV compared with the S1 and S2, where the specificity is of 100%. Moreover, the reported results indicated that the use of one single protein as a detection antigen of SARS-CoV infection may lead to false-positive diagnosis. These may be rectified by using more than one protein for the serodiagnosis of SARS-CoV.

scholarly journals Utility of Commonly Used Commercial Human Chorionic Gonadotropin Immunoassays in the Diagnosis and Management of Trophoblastic Diseases

2001 ◽  
Vol 47 (2) ◽  
pp. 308-315 ◽  
Author(s):  
Laurence A Cole ◽  
Shohreh Shahabi ◽  
Stephen A Butler ◽  
Hugh Mitchell ◽  
Edward S Newlands ◽  
...  
Keyword(s):  
Chorionic Gonadotropin ◽  
Human Chorionic Gonadotropin ◽  
False Positive ◽  
False Negative ◽  
Β Subunit ◽  
Serum Samples ◽  
Diagnosis And Management ◽  
Trophoblastic Diseases ◽  
Positive Results ◽  
Hcg Test

Abstract Background: Patients with trophoblastic diseases produce ordinary and irregular forms of human chorionic gonadotropin (hCG; e.g., nicked hCG, hCG missing the β-subunit C-terminal segment, hyperglycosylated hCG, and free β subunit) that are recognized to differing extents by automated immunometric hCG (or hCGβ) assays. This has led to low or false-negative results and misdiagnosis of persistent disease. False-positive hCG immunoreactivity has also been detected, leading to needless therapy for trophoblastic diseases. Here we compare seven commonly used hCG assays. Methods: Standards for five irregular forms hCG produced in trophoblastic diseases, serum samples from 59 patients with confirmed trophoblastic diseases, and serum samples from 12 women with previous false-positive hCG results (primarily in the Abbott AxSYM assay) were blindly tested by commercial laboratories in the Beckman Access hCGβ, the Abbott AxSYM hCGβ, the Chiron ACS:180 hCGβ, the Baxter Stratus hCG test, the DPC Immulite hCG test, the Serono MAIAclone hCGβ tests, and in the hCGβ RIA. Results: Only the RIA and the DPC appropriately detected the five irregular hCG standards. Only the Beckman, DPC, and Abbott assays gave results similar to the RIA in the patients with confirmed trophoblastic diseases (values within 25% of RIA in 49, 49, and 54 of 59 patients, respectively). For samples that were previously found to produce false-positive hCG results, no false-positive results were detected with the DPC and Chiron tests (5 samples, median &lt;2 IU/L), but up to one-third of samples were false positive (&gt;10 IU/L) in the Beckman (1 of 5), Serono (2 of 9), and Baxter assays (1 of 5), and the hCGβ RIA (3 of 9; median for all assays, &lt;5 IU/L). These samples, which produced false-positive results earlier in the Abbott AxSYM assay, continued to produce high values upon reassessment (median, 81 IU/L). Conclusions: Of six frequently used hCG immunometric assays, only the DPC detected the five irregular forms of βhCG, agreed with the RIA, and avoided false-positive results in the samples tested. This assay, and similarly designed assays not tested here, seem appropriate for hCG testing in the diagnosis and management of trophoblastic diseases.

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