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Results for “False Negative Reactions”

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At least 127 records · Page 7Linked to original sources
PubMed1990

Improved radioassay of anti-acetylcholine receptor antibody: application for the detection of extremely low antibody titers in sera from patients with myasthenia gravis.

We examined sera from 113 patients with myasthenia gravis (MG). Most of the patients with ocular MG without thymoma and 15% of the patients with generalized MG had immunoprecipitation (IP) titers of anti-acetylcholine receptor (anti-AChR) antibodies within the normal range for healthy subjects. We developed a highly sensitive radioassay using Staphylococcus aureus cells, and re-examined the 86 serum samples that had negative titers by IP. Using the radioassay, we detected anti-AChR antibodies in 27 (31%) of these myasthenic sera, of which 19 were from ocular MG patients without thymoma. By combining the standard IP assay and our new radioassay, we increased to 50% the overall percent positivity of detecting nonblocking-type antibodies in ocular MG patients without thymoma. We detected no anti-AChR antibodies in nearly all patients with various immunological and neurological diseases other than MG, and in all the healthy controls. The data for these sera indicate that in some cases the standard IP assay gives false-negative reactions. Thus, use of the more sensitive radioassay is preferable for accuracy.

Acetylcholine↗
PubMed1990

Determination of antibody from typhoid patients against lipopolysaccharide and protein antigens of Salmonella typhi.

Although the Widal test is simple, inexpensive and the most widely used for serodiagnosis of typhoid fever, the sensitivity and specificity of the test is sometimes doubtful. In this study, an enzyme-linked immunosorbent assay (ELISA) was developed for the detection of serum IgG and IgM antibodies to protein and lipopolysaccharide (LPS) antigens of Salmonella typhi which was compared with the Widal test in various groups of subjects. In typhoid patients with hemocultures positive for S. typhi (TP group), ELISA positivity was found on 100% for IgG antiprotein, 94.44% for IgG anti-LPS and 88.89% for IgM to both the protein and LPS antigens. In contrast, the Widal test was positive in only 61.11% for anti-O and 83.33% for anti-H antibodies. In healthy control subjects (HC group), only 5% of serum samples were positive for IgG anti-protein and none was positive for IgG anti-LPS or IgM to either the protein or LPS. In contrast, the Widal test was positive in 7.5% of HC group for anti-O and 17.5% for anti-H antibodies. In blood bank donors (BB group), both ELISA and Widal tests were positive in 23-40% of sera. Since the hospital records of BB group were incomplete. It might be possible that some of these subjects had recently been infected with S. typhi. Our data indicate that the standard Widal test was associated with false negative reactions in 16-39% of blood culture positive subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Bacterial↗
PubMed1975

The tuberculin tine and Mono-Vacc tests in the patient with active tuberculosis.

Eighty-four patients with culture-positive Mycobacterium tuberculosis infections of the lung were evaluated with the Mono-Vacc and tine tuberculin skin tests. A previous report indicated that false negative reactions with the tine may occur in up to 6 per cent of patients when it is used as a screening device for tuberculin sensitivity. However, as indicated by this study, it is unlikely that either screening tests would miss active tuberculous infection; no false negatives occurred in the 84 patients.

Adolescent↗
PubMed2001

Degradation of triglycidyl isocyanurate as a cause of false-negative patch test reaction.

Triglycidyl isocyanurate (TGIC) is mainly used in polyester-based powder paints, but also in laminates, insulating varnishes, coatings and adhesives. Several cases of contact allergy to TGIC have been reported during the last 10 years. Contact allergy to TGIC has developed in a factory producing the chemical, in a factory producing powder paints containing TGIC, and in industries using powder coating. In this paper, we report a man who developed a work-related dermatitis when working on the painting of metal frames. He was exposed to polyester powder pigments containing TGIC. When patch tested, he was negative to TGIC (prepared in 1988) 3x and positive to polyester powder pigment. Only when a new test preparation of fresh TGIC powder was tested, was a positive reaction obtained. Chemical analyses showed that there was no TGIC in the test preparation from 1988, and that in the TGIC powder from 1988, there was only 30% of the expected amount of TGIC. The investigations, clinical and chemical, strongly indicate degradation of TGIC in the test preparation and powder. Both substances and the test preparations made from them may change over time. Therefore, if a false-negative reaction due to a test preparation is strongly suspected, we recommend a re-test of the patient with a new test preparation of fresh material. As a general rule, patch testing should be performed with fresh substances and test preparations made from them, unless their stability and durability are known.

Adult↗
PubMed1989

Diagnosis of human hydatid disease in surgically-confirmed cases by the use of the indirect haemagglutination test based on a thermo-stable lipoprotein and on unfractionated hydatid cyst fluid.

A total of 204 sera, taken from healthy individuals or from individuals with various parasitic and bacterial infections, were examined by the indirect haemagglutination test. The tests were carried out using either a thermo-stable lipoprotein or unfractionated hydatid cyst fluid, and a titre of 1:64 or above was considered positive. Sixty-two of 70 sera from individuals with surgically-confirmed hydatid disease showed positive reactions with the thermo-stable lipoprotein--a sensitivity of 88%. No false positive reactions were obtained with sera from healthy individuals or from individuals with parasitic or bacterial infections, and no cross-reactions were observed with sera from individuals with multiple myeloma. The lipoprotein antigen thus showed a specificity of 100%. A sensitivity of 88% was obtained with the indirect haemagglutination test using whole hydatid cyst fluid; but positive reactions were obtained from healthy individuals and from individuals with schistosomiasis, leishmaniasis, taeniasis and malaria. No cross-reactions were obtained with sera from patients with gonorrhoea, syphilis or multiple myeloma. Because of the high sensitivity and specificity shown by the thermo-stable lipoprotein ('Antigen 880'), it is considered that this antigen is more useful than unfractionated hydatid cyst fluid in the diagnosis of human hydatidosis in Kenya.

Animals↗
PubMed2004

Pitfalls in diagnostic immunohistology.

The integration of immunostaining as an often-essential component of morphologic assessment makes it necessary that pathologists are familiar with the many technical and interpretive pitfalls that may arise because of the wide variety of factors that can significantly influence the ability to demonstrate relevant antigens in paraffin-embedded tissue sections. Pre-analytical variables that affect immunostaining include fixation, type of fixative, duration, temperature, and pH of fixation, variables in tissue processing, antigen loss resulting from delays in fixation, tissue necrosis, and levels of antigen expression. Analytical factors relate to the complex and sometimes capricious immunolabeling procedure that has as variables the specificity and sensitivity of the antibody clone, reagent dilution, detection system, and chromogen, and importantly, the method of antigen retrieval, which has its own set of variables such as time, temperature, method of heat generation, retrieval solution pH and molarity, and the synergistic action of proteolytic digestion. To obtain the highest diagnostic yield from immunostaining the correct questions must be asked and the pathologist must have familiarity with the characteristics of the antibody, its cross reactivity, if any, and localization of antigen in the cell to understand thresholds and cut-off levels and to recognize false-positive staining. Proper utilization of immunostaining requires that it is employed as a morphology-based technique and not interpreted in isolation.

Artifacts↗
PubMed1975

Severe histamine mediated reactions to intravenous drugs used in anaesthesia.

Severe histamine mediated reactions to intravenous drugs used in anaesthesia may occur as a result of anaphylactic and anaphylactoid reactions. The incidence is rare, but appears to be increasing. The difficulties in diagnosing such reactions and in determining the drug responsible and how these difficulties have led to confusion in the literature are discussed. Six cases of severe histamine mediated reactions are presented and detailed analyses of the drugs in these and other reported reactions is made showing varied clinical patterns with different drugs. The prevention, treatment, and follow-up of severe histamine mediated reactions are considered.

Adolescent↗
PubMed1982

Comparison of three prick test methods with the intradermal test and with the rast in the diagnosis of mite allergy.

Three prick test methods were compared in the diagnosis of mite allergy--the Morrow Brown standardized needle, the Multi-test device and a modified prick test. They were compared with the intradermal test and with specific IgE antibodies measured by RAST. Thirty patients and 10 control subjects were tested. The intradermal test was always positive in patients but induced two false positive reactions. All prick test methods gave false negative reactions. The Multi-Test device produced intermediate reactions between prick test and intradermal test.

Adolescent↗
PubMed1995

Comparison of a radioimmunoassay (Charm II) test with high-performance liquid chromatography for detection of oxytetracycline residues in milk samples from lactating cattle.

A radioimmunoassay test for tetracyclines (Charm II) was compared with high-pressure liquid chromatography (HPLC) for detection of oxytetracycline (OTC) residues in milk samples from individual lactating cows. Oxytetracycline was administered by 1 of 3 routes (IV, IM, or intrauterine) to 21 lactating dairy cows. A total of 292 duplicate milk samples were collected from milkings before and through 156 hours after OTC administration. Concentration of OTC in these samples was determined by use of the Charm II test and an HPLC method with a lower limit of quantitation, approximately 2 ng of OTC/ml. Samples were also classified with respect to presence of OTC residues relative to the FDA safe concentration (< or = 30 ng/ml), using the Charm II (by control point determination) and HPLC methods. There was a significant (P < or = 0.05) difference between test methods in classification of milk samples with respect to presence or absence of OTC at the FDA safe concentration. A total of 48 of the 292 test results (16.4%) did not agree. Using the HPLC test results as the standard with which Charm II test results were compared, 47 false presumptive-violative test results and 1 false presumptive-nonviolative Charm II test result (a sample containing 31 ng of OTC/ml, as evaluated by HPLC) were obtained. The samples with false presumptive-violative Charm II results contained < 30 ng of OTC/ml, as evaluated by HPLC. In some respects, the Charm II test performed appropriately as a screening test to detect OTC residues in milk samples from individual cows.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1981

Nickel allergy--reliability of patch test. Evaluated in female twins.

The recommended patch test procedure for nickel allergy with 5% NiSO4 in petrolatum was evaluated in a total of 169 female twins selected on the basis of a positive history of metal sensitivity. At the time of the evaluation most of them were healthy without current dermatitis. Of 88 female twins with a history of nickel sensitivity 62 (72%) had positive reactions after patch tests with 5% NiSO4 in petrolatum. In the remaining 26 the loss of epicutaneous reactivity was independent of age and time lapsed since the last episode of clinical dermatitis, and it did not occur more often in monozygotic than in dizygotic pairs. The number of negative reactions was greater after an exposure time of only 24 h than after 48 h. In 103 consecutive patients 2.5% NiSO4 in 50% DMSO or 5% NiCl in petrolatum were evaluated as possible alternative test substances. These tests produced a large number of irritant reactions and are therefore not suitable for routine use. One patient with a positive history of nickel allergy reacted negatively with 5% NiSO4 in petrolatum but had a true positive reaction with 5% NiCl. Obviously, 5% NiSO4 may give false negative reactions, and alternative test substances can therefore be useful in selected cases. In the present twin material positive nickel patch tests did not produce "angry back" reactions.

Aged↗
PubMed1998

Syphilis management and treatment.

Syphilis poses a serious health problem in many developing countries and in some areas of North America and Europe, especially Eastern Europe. This article initially addresses the state of the art regarding the interaction between syphilis and HIV infection and its consequences for management and treatment. Further attention is given to laboratory diagnosis of syphilis and false-positive and false-negative serologic reactions. The diagnosis and management of neurosyphilis, ocular, cardiovascular, and congenital syphilis are addressed, as well as management of syphilis patients allergic to penicillin and the Jarisch-Herxheimer reaction. Finally, the role of partner(s) and contact tracing is discussed.

Contact Tracing↗
PubMed2002

Development and use of a simple polymerase chain reaction assay to screen for Helicobacter spp. and H. hepaticus in intestinal and fecal samples from laboratory mice.

A simple and sensitive duplex polymerase chain reaction (PCR) assay was developed for use in detection of Helicobacter species and H. hepaticus in laboratory mice. Bacteria were extracted and concentrated from fecal pellets and intestinal segments by use of buoyant density centrifugation. To improve quality assurance, an internal control (mimic) for detection of false-negative reactions was included. In addition, cartridges (Capillette) pre-filled with PCR reagents, were used to minimize the hands-on time required, thus reducing the risk of contamination with previously amplified material. Laboratory mice from Swedish animal houses sent to the National Veterinary Institute for health monitoring were found to have high prevalence of H. hepaticus.

Animal Husbandry↗
PubMed1987

Evaluation of the ELISA for the serological diagnosis of trichinosis in Canadian swine.

An ELISA using a Trichinella spiralis spiralis excretory-secretory antigen was evaluated as a procedure for the diagnosis of trichinosis in swine in Canada. Field and experimental trials were carried out using both indirect serological (ELISA) and direct parasitological (pepsin-digestion) methods concurrently on serum and musculature, respectively, from each animal. The ELISA is a sensitive and specific test for the detection of Trichinella antibodies in porcine sera when present. The development of Trichinella antibodies appears to be dependent on the magnitude of the infection established, age of the infection when the animal is tested and the immunocompetence or response to infection of individual animals. False negative reactions were recorded in both field and experimental trials. In the field study, five of the 1009 swine examined were parasitologically positive with light infections ranging from 0.01 to 0.046 larvae per gram (la/g) of musculature yet all were serologically negative. Experimentally it was shown that Trichinella antibodies develop slowly, at least two to three months postinfection, in pigs with very light infections. Even in pigs which developed infections of 33 to 55 la/g of musculature, seroconversion occurred greater than 23 and less than 30 days postinfection. The immunocompetence or response to infection of individual pigs was variable as illustrated by one pig inoculated with 3000 infective larvae which had consistently lower titers compared to others in the same group despite the establishment of a muscle infection of 8.5 la/g of musculature. One false positive reaction was recorded in the experimental trial in an animal which had received 100 larvae and seroconverted at about three months postinfection.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗