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Results for “False Negative Reactions”

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PubMed2001

Validation of a polymerase chain reaction method for the detection of rendered bovine-derived materials in feedstuffs.

This study validated a polymerase chain reaction-based method for the detection of a specific bovine mitochondrial gene derived from rendered bovine tissues and admixed with complete animal feed. Four laboratories participated in this effort: one state laboratory and three Food and Drug Administration (FDA) laboratories, including one FDA field laboratory. The protocol used a statistical approach of 90% probability, with a 95% confidence interval for determining acceptable rates of false-positive and false-negative samples. Each participating laboratory analyzed 30 samples of feed each containing 0, 0.125, and 2.0% bovine meat and bone meal (BMBM), for a total of 90 feed samples. The samples were randomized such that the analysts were unaware of the true identity of the test samples. The results demonstrated that all laboratories met the acceptance criteria established for this protocol. The overall rates of false-negative results were 0.83% (1/120) at the level of 0.125% BMBM and 1.67% (2/120) at the level of 2% BMBM. The overall rate of false-negative results for all levels of BMBM was 1.25% (3/240). The rate for false-positive results was 0.83%.

Animal Feed↗
PubMed1985

Cerebrospinal fluid Histoplasma antibodies in central nervous system histoplasmosis.

We have evaluated the Histoplasma antibody response in the cerebrospinal fluid (CSF) in nine patients with central nervous system histoplasmosis and 98 controls. While the CSF Histoplasma antibody response identified eight of the nine patients, CSF cultures were positive in only two. Of controls with histoplasmosis but without meningitis (13 patients), or without histoplasmosis (85 patients), elevated CSF antibodies were detected by complement fixation in seven, by IgG radioimmunoassay in 17, and by IgM radioimmunoassay in five. Measurement of the CSF Histoplasma antibody response appears useful for identifying meningitis in patients with histoplasmosis, although cross-reactions occur in half of patients with other forms of chronic fungal meningitis. Patients with these other infections can usually be identified by tests for CSF Coccidioides antibodies, or cryptococcal antigens.

Antibody Formation↗
PubMed1998

Anomalies and the mental health professional.

Parental attitudes and reactions to the identification of fetal anomalies generally represent well-documented, normally occurring phenomena. The appropriate clinical management of such emotional reactions is an important responsibility of the medical units delivering care and services to the parents. Medical policy decisions about whether and when to screen for offspring anomalies is a considerably more complex and controversial topic. Attitudes, feelings, and reactions both of parents and professionals to the identification of fetal abnormality and fetal normality have come to play an increasingly important role in such policy decisions. Adequate evaluation of the topic requires scientifically based knowledge of the psychological and psychosocial effects of screening of normal-risk and high-risk cases, as well as the short-term and long-term consequences of true positive, true negative, false negative, and false positive identifications of offspring abnormality. Only partial answers to these questions are available to date, and further empirical work is needed.

Attitude to Health↗
PubMed2001

Acute posttraumatic stress: nonacceptance of early intervention.

Psychological resistance may be of considerable importance in the posttraumatic stress disorder (PTSD) population, considering that researchers in the field of traumatic stress are frequently unsuccessful in achieving high response rates, that many subjects suffering from PTSD never seek help, and that dropouts from therapy are frequent. This article presents data on the main complaints reported in the acute aftermath of an industrial disaster by 246 employees who had been exposed to the disaster. The dominant concerns were symptomatic complaints related to posttraumatic stress reactions rather than external problems. Sleep disturbance, anxiety/fear responses, and physical symptoms were reported by individuals with complaints in the acute phase as most problematic, while irritability and depressive symptoms appeared very infrequently among the reported main complaints. A high specificity and sensitivity were achieved in predicting later PTSD (as defined by DSM-III criteria) by applying early response variables: thus, there were few false-positives and false-negatives. There was a considerable overlap between the PTSD predictors and the main symptom complaints. From a prevention point of view, this should be advantageous, since it would bring the right people to seek help. However, in a significant proportion of the acutely distressed, the reluctance to seek help was motivated by the very symptoms that predicted PTSD. Even a relatively high rate of subjects agreeing to be screened (82.8%) would have lost 42% of those who qualified for a diagnosis of PTSD, and more than half of the subjects with severe outcomes would not have been included. For primary and secondary prevention, the findings suggest that early screening and outreach should be very active.

Accidents, Occupational↗
PubMed1976

[Interpretation of the results of various histochemical reactions used in pathological anatomy].

Some approaches to correct interpretation of indices of histochemical reactions most often used in pathologo-anatomic investigations are analysed on the basis of the author's personal observations and literature data. It is shown that direct interpretation of results of histochemical reactions according to the conventional scheme (negative reaction--the absence of the substrate in question, low-positive reaction--a low content, and highly positive reaction--a high content) is not always justifiable. One and the same histochemical phenomenon may have different meanings and reflect various functional states of the structure under study. To be able to reveal mechanisms underlying the changes in histochemical indices in experimental material and to determine the significance of this fact in every specific case, one should use a specially selected set of various histochemical and other research methods allowing the possibility of checking and correcting the indices obtained with the help of each of them.

Autopsy↗
PubMedDate not supplied

[Inhibitors of the polymerase chain reaction].

The information on the applied aspects of the polymerase chain reaction (PCR) is updated. In particular, the main inhibitor of PCR, considerably decreasing the sensitivity of the method both at the lysis stage of the tested material and due to the degradation of the DNA matrix and primers and/or to the direct inhibition of the activity of DNA polymerase, are described. The compounds, most frequently distorting the course of the reaction while testing clinical blood samples, bioptic samples, sputum, etc., are characterized. Testing concrete clinical material with the use of PCR was shown to require differentiated approach both at the stage of choosing the adequate method for the preparation of samples and at all other stages, including, e.g., the corresponding DNA polymerases or at the stage of heating for decreasing endonuclease activity or for IgG denaturation. Information on the causes of false negative results of PCR and the variants of their elimination, useful under practical laboratory conditions, is given.

False Negative Reactions↗
PubMed1979

[Aspects of immunologic diagnosis of brain tumors. Results with tumor-associated membrane antigens and the electrophoretic mobility test (author's transl)].

In cell-mediated immune processes the products of antigen-sensitive lymphocytes are detectable as charge-changing lymphokines by means of the cell electrophoretic mobility method (EM test). the improvement of the method concerns the measuring procedures (indicator particle and automation) and the application of specific antigens. The employment of special membrane antigens (3 M KCl extracts) from tissue of normal brain and brain tumors is decisive for further differentiating results. The application of tumor-associated membrane antigens (TAA) from various kinds of brain tumors shows some diagnostically important reaction patterns. Using a common tumor antigen, the TAA-X3 mixture, a (1) characteristic result of general significance for neoplasms can be obtained; in applying the different TAA of brain tumors the findings in EM test point out an (2) organospecific reactivity and/or a (3) histogenetic reaction pattern. The distinct neuroepithelial and mesodermal brain tumors produce predominantly an organospecific reaction and only partly a histogenetical profile. For this type of reactivity to the TAA in brain tumors, a series of factors depending on neuroimmunological specialities are important.

Adult↗
PubMed2000

Polymerase chain reaction in Lyme borreliosis.

Many bacterial and/or viral infections can affect several organs and apparatuses. Some of these infectious agents may be implicated in the pathogenesis and evolution of chronic connective and articular diseases. Such agents may trigger the start of articular chronic diseases or may play a role in maintaining the symptoms. In this study, we evaluated the sensitivity and specificity of polymerase chain reaction (PCR) in Lyme borreliosis, in patients with a confirmed diagnosis of the disease after clinical examination and standard serologic tests. There were 18 true positive results from nine samples from patients with present clinical signs, positive PCR, negative Western blot and/or enzyme-linked immunosorbent assay (ELISA) and nine samples with present clinical signs and positive ELISA and/or Western blot. The 51 true negative results were negative in all three methods used. There were 24 false positive results, positive for clinical signs, ELISA and/or Western blot but negative for PCR.

Blotting, Western↗
PubMed2006

Resolving repeatedly borderline results of Hybrid Capture 2 HPV DNA Test using polymerase chain reaction and genotyping.

The Hybrid Capture 2 HPV DNA Test (hc2) (Digene Corporation, Gaithersburg, MD) is at present the only FDA approved assay for routine detection of human papillomavirus (HPV) infections. A significant analytical inaccuracy of the hc2 near to cut-off was reported recently. To address this problem, 240 samples with repeatedly borderline/equivocal/indeterminate hc2 results (samples with repeated RLU/CO values between 0.4 and 4.0) were tested using the PGMY09/PGMY11 consensus PCR and genotyping in order to resolve their high-risk HPV status. All PGMY09/PGMY11 PCR negative samples were tested in addition using CPI/IIg consensus PCR. A false negative rate of 11.3% and false positive rate of 19.1% were recorded in the samples with repeatedly borderline hc2 results. The corresponding hc2 false reactivity rates in 95 samples selected at random which were clearly hc2 negative (samples with RLU/CO values less than 0.4) and 124 samples selected at random which were clearly hc2 positive (samples with RLU/CO values more than 4.0) were 4.2% and 5.6%, respectively. The proportion of hc2 false reactivity increased with proximity to the hc2 cut-off value. According to the results of the present study, the introduction of an hc2 grey-zone and retesting of samples with repeatedly borderline hc2 results by an alternate HPV detection method, such as the PGMY09/PGMY11 consensus PCR and genotyping, is recommended.

False Negative Reactions↗
PubMedDate not supplied

[Evaluation of counterimmunoelectrophoresis with antigens of icterohaemorrhagiae and patoc serovars in the serodiagnosis of human leptospirosis].

Counterimmunoelectrophoresis (CIE) was applied on paired sera from 135 patients with leptospirosis and on 69 sera from a control group. The sera from patients were subdivided in 4 groups according to the results obtained by the Microscopic Agglutination Test (MAT). The first samples sera from 58 patients were non reagent by MAT. Six monthly samples of sera were taken from 7 patients to follow-up and to determine the level of agglutinin and precipitin antibodies present using MAT and CIE. Serovars icterohaemorrhagiae and patoc were used as antigens. Three types of antigens were compared, 1) Triton-X-100 extracted; 2) heat extracted and 3) a pool of them. The CIE using icterohaemorrhagiae derived antigens types agreed with MAT in 92.64, 92.64 and 94.11% of the leptospirosis sera. The patoc antigens types reacted with the control group in 7.24, 86.95 and 84.05% of the samples, and consequently were eliminated from the present study. The icterohaemorrhagiae CIE reaction become positive earlier than MAT negative sera, and reverted to negative earlier in the follow-up samples from the patients. The CIE was sensitive and specific, gave rapid results and was easy to perform.

Agglutination Tests↗
PubMed2004

Evaluation of two real-time polymerase chain reaction pathogen detection kits for Salmonella spp. in food.

AIMS: To evaluate the LightCycler Salmonella Detection Kit and the TaqMan Salmonella Gold Detection and Quantitation Kit for the real-time PCR detection of Salmonella in various food samples. METHODS AND RESULTS: Ready-to-eat foods and raw food samples were artificially contaminated with Salmonella serotypes. In the specificity test, bacterial DNA extracted from sample pre-enrichment culture was analysed with the detection kits performed respectively on the LightCycler Instrument or the ABI Prism 7000 Sequence Detection System. No false-positive or false-negative results were obtained, although the LightCycler system generated invalid PCR results on two occasions. In the sensitivity test using the LightCycler system, Salmonella could be detected in pre-enrichment cultures of 25-g samples inoculated with as low as 1.5 x 10(3) CFU (depending on food type), and false-negative results were obtained for samples with low inoculum levels. CONCLUSIONS: Two commercial kits for real-time PCR detection of Salmonella were evaluated. SIGNIFICANCE AND IMPACT OF THE STUDY: Evaluation using more food types and matrices, and foods that contain low number of Salmonella or high number of other competing bacteria, is needed before adopting the real-time PCR technique for routine food tests.

Bacteriological Techniques↗
PubMed1988

The chick chorioallantoic membrane assay: an improved technique for the study of angiogenic activity.

The chick chorioallantoic membrane assay has been used for many years as an in vivo assay of angiogenic activity. However it has been plagued with the problem of a high incidence of false positive angiogenic responses. In this study the conventional chick chorioallantoic membrane assay was compared with a modification of this technique in a series of batches using a total of 100 eggs. False positive reactions were recorded in 32 out of 50 (64%) using the conventional method and only 11 out of 50 (22%) with the modified method (chi 2 = 17.992; p less than 0.001).

Amnion↗
PubMed1970

Studies towards the standardization of lepromin. Progress and prospects.

Because of the wide range of concentrations of Mycobacterium leprae in existing lepromins the authors studied methods of producing a standardizable lepromin containing 160 million bacilli/ml. The effects of using different dilutions of lepromin on the incidence of false-positive reactions were also studied.Progress reported includes a convenient method for preparing large batches of non-sedimenting lepromin, which is directly suitable for microscopic counting of Myco. leprae cells; and a validation of current methods for microscopic enumeration of Myco. leprae. Skin tests with diluted lepromins have demonstrated that dilutions up to 1:16 increase progressively the ability to distinguish between lepromatous and tuberculoid leprosy. This work has provided further evidence that 20 million bacilli/ml (a 1:8 dilution of the initial lepromin) should produce adequate Mitsuda reactions in general populations, provided that 3-mm reactions are taken as the criterion for 1+ positivity. The net effect of these findings is equivalent to expanding the world supply of lepromin by 8 times.Recommendations for further research are proposed.

Antigens↗
PubMed1976

[Evaluation of Brdicka's reaction in tumor diagnostic (author's transl)].

We have investigated the polarographic behaviour of sera from patients of an ORL-department by means of Brdicka reaction. It could be shown, that patients with cancer or acute inflammation had significantly increased values. But the arithmetic mean of this groups is enclosed by the scattering of the normal collective, therefore is no practically use for diagnostic purposes possible.

Carcinoma, Squamous Cell↗
PubMed2002

Comparative proteome bioinformatics: identification of a whole complement of putative protein tyrosine kinases in the model flowering plant Arabidopsis thaliana.

Phosphorylation by protein tyrosine kinases is crucial to the control of growth and development of multicellular eukaryotes, including humans, and it also seems to play an important role in multicellular prokaryotes. A plant tyrosine-specific kinase has not been identified yet; hence, plants have been suggested to share with unicellular eukaryote yeast a tyrosine phosphorylation system where a limited number of stress proteins are tyrosyl-phosphorylated only by a few dual-specificity (serine/threonine and tyrosine) kinases. However, preliminary evidence obtained so far suggests that tyrosine phosphorylation in plants depends on the developmental conditions. Since sequencing of the genome of the model flowering plant Arabidopsis thaliana has been recently completed, we have performed a bioinformatic screening of the whole Arabidopsis proteome to identify a model complement of bona fide protein tyrosine kinases. In silico analyses suggest that < 4% of Arabidopsis kinases are tyrosine-specific kinases, whose gene expression has been assessed by a preliminary polymerase chain reaction screening of an Arabidopsis cDNA library. Finally, immunological evidence confirms that the number of Arabidopsis proteins specifically phosphorylated on tyrosine residues is much higher than in yeast.

Amino Acid Sequence↗
PubMed1983

The role of contact thermography in the diagnosis of deep venous thrombosis.

Contact thermography, a non-invasive inexpensive method of investigation for the diagnosis of deep venous thrombosis in the lower limb, was compared with conventional ascending phlebography in 69 patients. The results showed a diagnostic sensitivity of 97% and a diagnostic specificity of 50% giving an overall agreement of 73% between the methods. The low diagnostic specificity of thermography was to be expected, since any inflammatory reaction, whatever the cause, will give a rise in the skin-temperature. The high sensitivity shows that thermography is useful as a screening method. In the present material thermography could have prevented 25 per cent of the phlebographies.

Adult↗
PubMed1988

Comparison of diagnostic methods in latex surgical glove contact urticaria.

Surgical rubber gloves contain allergens derived from natural rubber latex which may sensitize, causing contact urticaria and even systemic reactions. We examined 15 hospital employees allergic to latex surgical gloves, using various skin tests and RAST, to determine the most reliable diagnostic method and to investigate coexistent allergy to glove powder and rubber chemicals. Prick testing using a stock solution made from one brand of latex glove yielded positive (2+ to 4+) reactions in all 15 employees: 8 retained positive reactions at a 1/10 dilution, 1 at 1/100 and 4 at 1/1000. A prick test using rubber-tree sap (Hevea brasiliensis) was positive in 12/15 employees and a scratch-chamber test using crushed rubber-tree leaf was positive in 13/15. A latex glove use test was positive in 12/13 employees and a latex RAST detected measurable amounts of specific IgE in 8/15. No positive prick test reactions were obtained using glove powder. On patch testing, 2/15 employees showed delayed allergy to rubber chemicals but no immediate reactions were detected. The present results indicate that in addition to the use test, prick testing with a stock solution prepared from latex surgical gloves is an adequate test method for routine practice when diagnosing latex glove contact urticaria. The correlation between prick tests and whole glove use tests was good, but latex RASTs yielded some negative results.

Adult↗
PubMedDate not supplied

The use of novel stimuli as indicators of aggressive behavior in dogs.

To test the predictive value of a doll and an artificial hand, reactions of dogs (n=100) were compared to histories of behavior toward children. Each dog's reaction to the doll and the hand was categorized as normal, fearful, fearfully aggressive, or offensively aggressive. Sixty-five percent (n=37) of the dogs that had a normal or no reaction to the stimuli had a history of being good with children. Eighty-eight percent (n=34) of the dogs that had an aggressive reaction to the doll had a history of aggressive behavior toward a child. Dogs that were fearfully aggressive were significantly more likely to show fearful responses to the doll, and dogs that were either dominant or fearfully aggressive were more likely to exhibit aggression of the same type to the hand. The results of this study indicate that the doll and, to a lesser extent, the hand may be useful components in determining the aggressive tendencies of dogs. The results also point out the major limitations, because the false positives and false negatives are too frequent.

Aggression↗