SEARCH · Search PubMed

Results for “False Negative Reactions”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 343 records · Page 19Linked to original sources

PubMed1989

False-positive results with third-generation monoclonal hepatitis B surface antigen enzyme immunoassay.

Nonspecific hepatitis B surface antigen reactions with a third-generation enzyme immunoassay (Auszyme Monoclonal; Abbott Laboratories, North Chicago, Ill.) were investigated with 9,577 serum specimens in a clinical laboratory setting. Of the 196 serum specimens found reactive in Auszyme screen by the overnight procedure, 103 turned out to be true-positives, 71 were nonrepeatably reactive, and 22 were repeatably reactive but actually falsely positive (false-positive rate, 22 of 196, or 11.2%). Verification of the 196 screen reactives by the Auszyme 3-h incubation assay detected all but 4 true-positives, with a false-negative rate of 3.9% (4 of 103), and was negative for the rest. These observations reinforce the need for retesting all reactive specimens and confirming repeatedly reactive samples when the Auszyme Monoclonal test is used to detect hepatitis B surface antigen.

Carrier State↗

PubMed1981

Rapid and direct staphylocoagulase assay that uses a chromogenic substrate for identification of Staphylococcus aureus.

A rapid and direct assay of staphylocoagulase that uses chromogenic substrate Chromozym TH was developed for the routine identification of Staphylococcus aureus. False-positive and false-negative reactions were eliminated by measuring the activity of staphylocoagulase-prothrombin complex directly. The method was compared with three clotting assays. The results show that the new assay is specific, quantitative, and easily automated. If offers clinical laboratories a more reliable assay of staphylocoagulase and is a valuable aid for the rapid identification of S. aureus.

Blood Coagulation↗

PubMed2005

The "spanning protocol": a new DNA extraction method for efficient single-cell genetic diagnosis.

PURPOSE: We evaluated methods of preparation of DNA from single cells for amplification and preimplantation genetic diagnosis (PGD), including our "spanning protocol." METHODS: Dystrophin gene exons 45 and 51 were amplified by nested polymerase chain reaction (PCR) from a single lymphocyte or blastomere. Amplification efficiencies were compared between DNA extraction by (A) lysis in distilled water with freeze-thawing and boiling; (B) two-step lysis involving potassium hydroxide and dithiothreitol; and (C) the spanning protocol, using N-lauroylsarcosine. RESULTS: With method A, amplification efficiency was 66/120 (55%) and false-positive such as amplification failure or allele drop out was 42/120 (35%); with B, 96/120 (80%) and 21/120 (17.5%); and with C, 111/120 (92%) and 5/120 (4.2%), using single blastomeres and unaffected lymphocytes from male. Occurrence of false-negative such as contamination of another DNA with method A was 4/120 (3.3%); with B, 10/120 (8.3%); and with C, 2/120 (1.7%) from using single lymphocytes from affected males. CONCLUSION: The spanning protocol was most efficient for extracting DNA from a single cell and should be particularly useful for preimplantation genetic diagnosis.

Blastomeres↗

PubMed2006

The implications of 18F-FDG PET for the diagnosis of endoprosthetic loosening and infection in hip and knee arthroplasty: results from a prospective, blinded study.

BACKGROUND: The most frequent complications of joint arthroplasty are septic or aseptic loosening of endoprostheses. Preoperative differentiation is essential, since very different treatment methods result from the diagnoses. The aim of the current study was to evaluate the clinical value of 18F-Fluoro-deoxyglucose positron emission tomography (18F-FDG PET) as a diagnostic modality for inflammation and loosening in hip and knee joint prostheses. METHODS: 18F-FDG-PET examinations and multiphase bone scan were performed on hip and knee endoprostheses in 27 patients prior to revision surgical procedures planned for prosthetic loosening. Intact prostheses were found at the opposite site in some patients so that additional 9 joints could be examined with the field of view of 18F-FDG PET. Verification and valuation of the PET and scintigraphic image findings were conducted by comparing them with information combined from intraoperative findings, histopathology, and microbiological investigations. RESULTS: Evidence of loosening was correctly determined in 76.4% of cases using 18F-FDG-PET, and in 75% of cases using bone scan. The detection of periprosthetic inflammation using 18F-FDG-PET had a sensitivity of 100% for septic cases and of 45.5% in cases of increased abrasion and aseptic foreign-body reactions. However, reliable differentiation between abrasion-induced and bacterial-caused inflammation was not possible using 18F-FDG-PET. CONCLUSION: 18F-Fluoro-deoxyglucose positron emission tomography (18F-FDG-PET) allows reliable prediction of peri-prosthetic septical inflammatory tissue reactions. Because of the high sensitivity of this method, a negative PET result in the setting of a diagnostically unclear situation eliminates the need for revision surgery. In contrast, a positive PET result gives no clear differentiation regarding the cause of inflammation.

Aged↗

PubMed1993

Reliability of polymerase chain reaction for detection of hepatitis C virus.

The polymerase chain reaction (PCR) is used to detect hepatitis C virus (HCV) RNA, and the results of this assay may have a bearing on management of patients. We tested 31 laboratories for performance of HCV PCR with a coded panel that comprised 4 HCV-positive plasma samples, 6 HCV-negative samples, and two dilution series of HCV-positive plasma. 15 (48%) laboratories had faultless results with both dilution series, and 16 (52%) laboratories reported erroneous results with one or both series. 10 (32%) laboratories had faultless results when testing undiluted plasma samples, 11 (35%) produced a false-negative result with a weak-positive sample, and 10 (32%) produced false negative and/or false positive results. Only 5 (16%) laboratories performed faultlessly with the entire panel of samples. Reports of presence of HCV should be interpreted with care until reliable HCV-RNA detection becomes widely available.

Clinical Laboratory Techniques↗

PubMed1998

A second European collaborative study on polymerase chain reaction for Toxoplasma gondii, involving 15 teams.

In order to investigate the accuracy and practicability of the polymerase chain reaction (PCR) in the antenatal diagnosis of congenital toxoplasmosis, a collaborative study involving 15 European laboratories was performed under the auspices of the Biomed 2 Programme of the European Community. Each team received 12 aliquots (four negative, eight positive) of 'artificial samples' made of amniotic fluid spiked with tachyzoites of the RH strain of Toxoplasma gondii. Each team performed its own PCR protocol (all were different). Nine of the 15 laboratories were able to detect a single parasite, but two of the 15 found all samples negative. Four of the 15 laboratories found one or more control samples to be falsely positive. This study highlights the lack of homogeneity between PCR protocols and performance and underlines the need for an external quality assurance scheme which could provide 'reference' samples that could be used by any laboratory wanting to establish and maintain an accurate diagnostic test based on PCR.

Amniotic Fluid↗

PubMed1993

Evaluation of the polymerase chain reaction for diagnosis of herpes simplex virus encephalitis.

Cerebrospinal fluid samples from 257 patients with suspected herpes simplex virus encephalitis were prospectively analyzed by herpes simplex virus polymerase chain reaction. The polymerase chain reaction indicated herpes simplex virus encephalitis in 9 serologically proven cases and in 14 additional patients. Increased polymerase chain reaction signals were observed together with more severe neurological symptoms (P < 0.01) and within the first days of acyclovir treatment (P < 0.05).

Acyclovir↗

PubMed1987

Disease activity in osteomyelitis: role of radiography.

To determine the impact of radiographic findings on the interpretation of bone and gallium scans of patients with active osteomyelitis, the authors reviewed the medical records and radiologic examinations of 104 patients. The only diagnostic finding of active disease on radiographs was the presence of a sequestrum (three patients). Other findings--such as erosion, soft-tissue swelling, and periosteal reaction--proved nonspecific and did not differentiate active from inactive disease. Furthermore, these findings did not significantly change the sensitivity or specificity of the bone and gallium scans, either in detecting or in excluding the presence of active disease.

Adolescent↗

PubMed1996

Interlaboratory comparison of polymerase chain reaction for the detection of Toxoplasma gondii DNA added to samples of amniotic fluid.

To investigate the accuracy of the polymerase chain reaction (PCR) method for the detection of Toxoplasma gondii in clinical specimens, aliquots of amniotic fluid to which known amounts of Toxoplasma gondii DNA had been added were tested by five European Centres. Four laboratories were able to detect DNA at levels equivalent to ten tachyzoites or less, including two that detected DNA equivalent to a single parasite. Two laboratories erroneously found one of eight negative control samples to be positive. These findings confirm that the high level of sensitivity associated with the PCR method can be readily achieved under routine laboratory conditions, but they also underscore the potential for both false-positive and false-negative findings to occur. Furthermore, the results confirm the urgent need for an external quality assurance scheme to support laboratories employing PCR in a clinical context for the detection of Toxoplasma gondii.

Amniotic Fluid↗

PubMed1991

Epidemiologic critique of the report on adverse reactions to ionic and nonionic media by the Japanese Committee on the Safety of Contrast Media.

The author takes a critical look at the findings of the Katayama study of adverse reactions to ionic and nonionic contrast media. The author suggests that although the relative risks appear to be large and favor the use of nonionic media, serious adverse reactions were infrequent with both media types and risks were small on an absolute scale. In addition, the study demonstrates the potential for several serious information and selection biases. The accuracy of risk estimates are therefore called into question. Nevertheless, this study is extremely important in clarifying the risks associated with ionic and nonionic media during venography.

Contrast Media↗

PubMed1977

Characterisation of immunofluorescent heterophile antibodies which may be confused with autoantibodies.

Approximately 6% of sera submitted for routine immunofluorescent autoantibody screeening produced characteristic reaction patterns against a variety of animal and human tissues. It is suggested that these non-tissue-specific patterns represent a complex family of heterophile antibodies which could be confused with certain autoantibodies. It is further suggested that these heterophile antibodies bear a relationship to IgG isohaemagglutinins.

Animals↗

PubMed2005

Automated cerebrospinal fluid cytology: limitations and reasonable applications.

OBJECTIVE: To evaluate the precision and clinical applicability of the Bayer ADVIA 120 cytometer (Bayer Healthcare, Fernwald, Germany) for cerebrospinal fluid (CSF) cell count and differentiation. STUDY DESIGN: One hundred six analyses of CSF from 98 patients by the ADVIA 120 were compared with routine cell count and microscopic differentiation. Correlation coefficients were calculated. RESULTS: In general, the total cell counts of both methods correlated well. The best correlations were seen at higher cell counts, > or = 100 cells per microliter with < 100 erythrocytes per microliter. The best correlations of cell differentiation were seen for lymphocytes and neutrophils, while the results for monocytes and eosinophils were less precise. In some cases, considerable differences between automated and microscopic cell counts and differentiation were seen that were relevant to clinical decision making. The detection of pathologic cell types, such as hemosiderophages, mitoses and neoplastic cells, was not provided by automated cytometry. CONCLUSION: When experienced personnel are not available, a preliminary cell count and differentiation between neutrophilic and lymphocytic reactions by automated cytometry may be valuable in allowing initial therapeutic decision making. Since the detection of pathologic cell types is not provided and the precision at low cell counts is only moderate, a personal microscopic evaluation of each sample is still indispensable to avoid misdiagnoses.

Cell Count↗

PubMed1984

Pregnancy tests: evaluation of current status.

During the past 2 decades, laboratorians have observed many changes in pregnancy tests, which are generally defined as procedures designed to detect elevated levels of hCG in urine and/or serum. The original tests were animal assays in which biologic changes were observed following the injection of urine. The currently most widely utilized tests are slide and tube tests, including some of with beta-subunit specificity, in which urine hCG is detected by immunologic antigen-antibody reactions. Finally, in some settings there has been increased testing for hCG by radioreceptor assays based on the binding of hCG to plasma membrane receptor sites and qualitative radioimmunoassay utilizing classic competitive binding techniques. This review compares the relative advantages and disadvantages of these procedures in regard to diagnostic effectiveness, sensitivity, specificity, cost variables, and technical requirements.

Agglutination Tests↗

PubMed2005

Variability of quantitative polymerase chain reaction detection of the bcl-2-IgH translocation in an international multicenter study.

The t(14;18)(q32;q21) chromosomal translocation is closely associated with follicular lymphoma. Polymerase chain reaction (PCR) analysis has high sensitivity and is used to assess responses to therapy. Quantification of translocation-bearing cells is a possible advantage of real-time PCR over conventional PCR. A collaborative study comparing results from 12 international laboratories is reported.

Biomarkers, Tumor↗

PubMed1986

Tuberculin testing in the young.

The child with a positive tuberculin reaction or uncomplicated primary tuberculosis rarely has symptoms. Since INH prophylaxis for one year will practically always prevent the severe forms of tuberculosis, early diagnosis is essential. An annual or biennial tuberculin test is recommended, and is always indicated when there has been known contact with a tuberculous adult. The Mono-Vacc test is a satisfactory screening device.

Adrenal Cortex Hormones↗

PubMed1996

Prevention of false results from preferential PCR amplification or VNTR alleles.

In forensic DNA typing, evidential samples generally involve limited amounts of DNA and so should be carefully utilized. Although polymerase chain reaction (PCR) of variable number of tandem repeats (VNTR) alleles is the prevailing method for forensic identification, the fidelity of amplification of heterozygous VNTR alleles with large disparities in length needs to be carefully examined. Reports in the literature and our own observations have demonstrated that PCR artifacts, bogus alleles and allelic drop-out of VNTRs, are related to the amount of genomic DNA, the number of amplification cycles and the length of alleles amplified. Two small (< 1 kb) hypervariable VNTRs (Apo B and HVR-Ig) markers used for forensic identification were chosen to study these relationships. The results revealed that PCR amplification for the heterozygous VNTR alleles with wide disparity in length (> 400 bp) easily produced the allelic drop-out problem and therefore, led to the false results; and the allelic fragment of PCR products was preferentially lost after only 2 cycles of overamplification. We also further established the relationship between the optimal number of amplification cycles and the amount of genomic DNA in the reaction mixture. In our routine forensic screening this relationship has been successfully applied to determine the optimal number of amplification cycles and to avoid the allelic drop-out problem and achieve fidelity of PCR-VNTR amplification. It has also been used to investigate forensic casework.

Alleles↗

PubMed1980

[Enzymo-immunologic determination of the class of antiglobulin factors].

The authors describe an enzymo-immunologic method of determination of the class of rheumatoid factors (RF). This technic includes 3 main stages : 1) extraction of RF by fixation on aggregated rabbit IgG previously adsorbed on the walls of a plastic tube; 2) recognition of RF linked to the solid phase by anti-IgG addition, and addition of human IgA and IgM linked to glucose oxidase; 3) revelation of the enzyme activity linked to the solid phase : this enzyme activity directly depends on the levels of RF to be estimated. The results are expressed as a percentage of the fixation of a reference serum obtained from a patient with rheumatoid arthritis (RA). This serum presents an antiglobulin activity in the 3 major classes of immunoglobulins. The coefficients of variation of intra- and intersystem reproductibility lay between 5,6 and 17.8%. The specificity of the estimation was controlled by the localisation of the antiglobulin activity of the sera after chromatography on Sephadex G200 and by estimation of RF after their absorption by an aggregated IgG immunoadsorbant. This technic was applied to the identification of RF in RA (90 cases); in diseases not related to RA and in control subjects : the sensitivity of this method appears greater than that of technics previously described (immuno-fluorescence, Rose-Waaler reaction) in fact, only 12,2% of sera of patients with RA remain negative with this new test. However, this greater sensitivity does not seem to have altered the clinical specificity of the test : in fact, only 8,4% of the sera of patients with diseases unrelated to RA are positive by this method, which, moreover, may be explained by the age of these subjects (average age 71.5 years).

Aged↗

PubMed2000

Standardization and quality control of PCR analyses.

In the very beginning of polymerase chain reaction (PCR) tests entering the field of diagnosis of infectious agents, the introduction of this technology into routine diagnosis was hampered by its frequent tendency to create false-positive results because of contamination. This problem is now widely solved by the introduction of the uracil-N-glycosylase (UNG) anticontamination technology. However, care must still be taken to avoid other sources of producing false positive results. They might additionally derive from human error and/or insufficient PCR amplification and detection protocols. A special case lies in the fact that PCR also amplifies DNA from dead organisms rendering a result diagnostically correct as positive, but clinically as false-positive. In PCR, as in any other diagnostic test, the risk of creating a false-negative result also exists. In such a case, the most probable source besides human error, low target or poor amplification and detection protocols is an inhibition caused by interfering substances in a patient's sample. Strategies to recognize and overcome this issue are discussed in this article. Finally a few results from quality control studies on amplification technologies in the diagnosis of infectious agents are reviewed.

False Negative Reactions↗