Long-term Persistence of False Positive Antibody Reactivity in HIV Western Blot Testing of Sera from a Healthy Blood Donor

ABSTRACTA study comparing the ICT (immunochromatography technology)ToxoplasmaIgG and IgM rapid diagnostic test (LDBio Diagnostics, France) with a fully automated system, Architect, was performed on samples from university hospitals of Marseille and Saint-Etienne. A total of 767 prospective sera and 235 selected sera were collected. The panels were selected to test various IgG and IgM parameters. The reference technique,ToxoplasmaIgGII Western blot analysis (LDBio Diagnostics), was used to confirm the IgG results, and commercial kits Platelia Toxo IgM (Bio-Rad) and Toxo-ISAgA (bioMérieux) were used in Saint-Etienne and Marseille, respectively, as the IgM reference techniques. Sensitivity and specificity of the ICT and the Architect IgG assays were compared using a prospective panel. Sensitivity was 100% for the ICT test and 92.1% for Architect (cutoff at 1.6 IU/ml). The low-IgG-titer serum results confirmed that ICT sensitivity was superior to that of Architect. Specificity was 98.7% (ICT) and 99.8% (Architect IgG). The ICT test is also useful for detecting IgM without IgG and is both sensitive (100%) and specific (100%), as it can distinguish nonspecific IgM from specificToxoplasmaIgM. In comparison, IgM sensitivity and specificity on Architect are 96.1% and 99.6%, respectively (cutoff at 0.5 arbitrary units [AU]/ml). To conclude, this new test overcomes the limitations of automated screening techniques, which are not sensitive enough for IgG and lack specificity for IgM (rare IgM false-positive cases).

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Systematic Review: The Long-Term Effects of False-Positive Mammograms

Annals of Internal Medicine ◽

10.7326/0003-4819-146-7-200704030-00006 ◽

2007 ◽

Vol 146 (7) ◽

pp. 502 ◽

Cited By ~ 283

Author(s):

Noel T. Brewer ◽

Talya Salz ◽

Sarah E. Lillie

Keyword(s):

Systematic Review ◽

False Positive ◽

Long Term Effects

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Toxocariasis/cysticercosis seroprevalence in a long-term rural settlement, São Paulo, Brazil

Parasitology ◽

10.1017/s0031182009005769 ◽

2009 ◽

Vol 136 (6) ◽

pp. 681-689 ◽

Cited By ~ 13

Author(s):

L. E. PRESTES-CARNEIRO ◽

D. H. P. SOUZA ◽

G. C. MORENO ◽

C. TROIANI ◽

V. SANTARÉM ◽

...

Keyword(s):

Western Blot ◽

Taenia Solium ◽

Sao Paulo ◽

Rural Settlement ◽

São Paulo ◽

Educational Levels ◽

Second Stage ◽

Paulo State ◽

Ocular Manifestations

SUMMARYSeroprevalence of Toxocara and Taenia solium and risk factors for infection with these parasites were explored in a long-term rural settlement in São Paulo state, Brazil. An ELISA for the detection of anti-Toxocara IgG and IgE and anti-T. solium cysticerci was standardized using Toxocara excretory-secretory antigens (TES) obtained from the cultured second-stage larvae of T. canis and by vesicular fluid antigen from Taenia crassiceps cysticerci (VF). For cysticercosis, the reactive ELISA samples were assayed by Western blot using 18 kDa and 14 kDa proteins purified from VF. Out of 182 subjects, 25 (13·7%) presented anti-Toxocara IgG and a positive correlation between total IgE and the reactive index of specific anti-TES IgE (P=0·0265) was found amongst the subjects found seropositive for anti-Toxocara IgG. In these individuals 38·0% showed ocular manifestations. The frequency of anti-T. solium cysticerci confirmed by Western blot was 0·6%. Seropositivity for Toxocara was correlated with low educational levels and the owning of dogs. Embryonated eggs of Toxocara spp. were found in 43·3% of the analysed areas.

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False-Positive D-Dimer Result in a Patient With Castleman Disease

Archives of Pathology & Laboratory Medicine ◽

10.5858/2004-128-328-fdriap ◽

2004 ◽

Vol 128 (3) ◽

pp. 328-331

Author(s):

Kimberly Mugler ◽

Jerry B. Lefkowitz

Keyword(s):

Western Blot ◽

Disseminated Intravascular Coagulation ◽

False Positive ◽

Degradation Products ◽

False Negative ◽

Castleman Disease ◽

Laboratory Findings ◽

Intravascular Coagulation ◽

Immunodeficiency Virus ◽

D Dimer

Abstract In suspected cases of disseminated intravascular coagulation, concurrent elevation of both fibrin(ogen) degradation products (FDPs) and D-dimer levels aids in confirming the diagnosis. This pattern of results reflects the action of plasmin proteolysis of cross-linked fibrin polymers as well as fibrinogen. We report the case of a patient with human immunodeficiency virus (HIV) and Castleman disease who presented with a high-positive D-dimer level and a negative FDP level in the course of a workup for disseminated intravascular coagulation. This finding suggested the possibility of either a false-positive D-dimer or a false-negative FDP level. To investigate the former, a Western blot was performed on the patient's serum to determine the presence of the D-dimer. No D-dimer band was visualized on the Western blot, confirming the false-positive nature of the D-dimer result. Insufficient quantity of patient serum, however, prevented further investigation into the etiology of this result. The false-positive D-dimer result is likely attributable to interference caused by the patient's Castleman disease–associated monoclonal gammopathy, a phenomenon that has been reported in other immunoassays. As the development of lymphoproliferative disorders is especially common within the HIV population, and hypergammaglobulinemia in Castleman disease is particularly common, clinicians should be aware of this phenomenon when the laboratory findings do not fit the clinical picture. Although it is rare, recognition of potential paraprotein interference in immunoassays will help avoid undertreatment or overtreatment of patients based on erroneous laboratory results.

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