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PubMed1988

Significance of false positive syphilis reactions and anticardiolipin antibodies in a nationwide series of pregnant women.

The highly sensitive rapid plasma reagin (RPR) and Treponema pallidum hemagglutination tests were used to determine the frequency of false positive syphilis reactions in a nationwide series of pregnant women in Finland. The frequency found was 14/10,000. Two cases of systemic lupus and 2 of undefined connective tissue disease were found during a 20-month period among 134 false positive reactors in a series of 110,000 separate pregnancies. The risk of subsequent fetal loss among false positive syphilis reactors was 7%, similar to the risk in RPR negative controls. Half of the sera in the highest RPR titer groups and 1/3 in the lowest titer groups had elevated levels of anticardiolipin antibodies in solid-phase enzyme immunoassay. This assay did not increase the risk of clinical disease or subsequent fetal loss above the risk of RPR test alone.

Adult↗
PubMed1981

Bacteria associated with false-positive most-probable-number coliform test results for shellfish and estuaries.

Aerobic and facultatively anaerobic bacteria isolated from false-positive, presumptive, total coliform, most-probable-number tests of Chesapeake Bay oyster, water, and sediment samples were characterized and then classified by numerical taxonomy. A total of 538 bacterial strains clustered into 17 phena, the predominant groups of which were Enterobacteriaceae (including Escherichia coli), Aeromonas spp., and Bacillus spp. Bacillus spp. were recovered most frequently from sediment samples. Gas-producing strains which were not members of the Enterobacteriaceae were not isolated during this study. However, disproportionately large numbers of atypical and anaerogenic lactose-fermenting strains were encountered. We concluded that no single, specific bacterial group can be identified as being responsible for the false-positive reaction in the presumptive coliform test. Instead, the false-positive reaction is a result of complex interactions among various genera, representing predominantly bacteria other than coliforms.

Animals↗
PubMed1990

Use of polymerase chain reaction for successful identification of asymptomatic genital infection with herpes simplex virus in pregnant women at delivery.

The polymerase chain reaction was adapted to the amplification of a herpes simplex virus (HSV) DNA sequence, common to HSV types 1 and 2 (HSV-1, HSV-2). The amplified product was detectable by ethidium-bromide staining or Southern hybridization of gels and by dot hybridization. The HSV polymerase chain reaction detected HSV DNA in samples obtained from eight patients with genital lesions from which HSV-2 was isolated in tissue culture and from four patients with labial lesions from which HSV-1 was isolated. The HSV polymerase chain reaction identified HSV in clinical specimens obtained from 11 women who had asymptomatic genital HSV infections at delivery. None of 11 samples obtained at delivery from women who had antibodies to HSV-2, but whose delivery cultures were negative, were positive by polymerase chain reaction and no false-positive reactions were obtained when the reaction mixture contained human cell DNA or varicella-zoster virus, cytomegalovirus, Epstein-Barr virus, or human papillomavirus DNA.

Blotting, Southern↗
PubMed1983

Angry back or the excited skin syndrome. A prospective study.

Allergens eliciting weak positive reactions were retested to ascertain their reproducibility. Weak positive patch test reactions, concomitant to other weak or strong positive reactions, were retested after 3 weeks in 61 patients. 79 reactions were retested; 35 (44.3%) were negative. Allergens which are marginal irritants, e.g., formaldehyde, often gave weak positive reactions which were lost at retesting. In patients without dermatitis but with several strong positive reactions, lost reactions were frequently encountered, suggesting that strong reactions induced a state of hyperirritability. False positive reactions were often found in the proximity of strong reactions. We attempted to develop a nonspecific irritant (sodium lauryl sulfate) as a hyperirritability marker. A correlation between the score of this test and false positive reactions was not found. It is concluded that weak positive reactions should not be accepted as a proof of sensitization. The allergens eliciting these reactions should be retested at a later date.

Adolescent↗
PubMed1977

The use of bovine PPD tuberculin the single caudal fold test to detect tuberculosis in beef cattle.

The efficiency of 2 different doses of bovine PPD tuberculin was compared using the caudal fold test for the detection of tuberculosis in beef cattle. Two matched groups of 98 cattle were selected on the basis of their reactivity to HCSM tuberculin. Cattle in each group were tested with a singl 0.1 ml dose of bovine PPD tuberculin containing either 0.1 mg or 0.2mg bovine PPD respectively. Two further groups of 100 young stock from a herd with an incidence of tuberculosis of less than 0.1% were selected as controls. Tests were interpreted subjectively by palpation and observation and objectively by caliper measurement at 48, 72 and 96h. All cattle were examined post mortem for the presence of visible lesions. The 0.2 mg dose of PPD detected 95% tuberculous cattle and caused false-positive reactions in 19% of cattle without lesions. The 0.1 mg dose detected 80% of tuberculous cattle and caused 11% false-positive reactions. No visible lesions of tuberculosis were found in either of the control groups although 11% reacted to 0.2 mg and 5% to 0.1 mg bovine PPD at 72h. The optimum time for reading tuberculin tests was found to be in the period 48 to 72h after the injection of bovine PPD and subjective interpretation was more efficient than caliper measurement as a means of detection of tuberculous cattle. The 0.2 mg dose of bovine PPD was found to be more specific than HCSM tuberculin.

Animals↗
PubMed1978

[Irregular antibody screening by Groupamatic at the Paris (C.N.T.S.) and Toulouse (C.R.T.S.) blood transfusion centers].

We report here the experience of 3 years of irregular antibody automated screening with Groupamatic, that is to say of 661,511 samples tested in Paris and 269, 162 samples tested in Toulouse. The positive reactions in Paris were 16,296 (2.46%) out of which 2,021 irregular antibodies were identified (0.30%). The positive reactions in Toulouse were 8,266 (3.07%) out of which 2,138 irregular antibodies were identified (0,79%). The difference between the number of screened positive reactions and the identified one is due to false positive reactions (half of the cases) and to autoantibodies whose number is roughly the same than the number of identified alloantibodies. During the years 1970, 1971 and 1972, the irregular antibodies were systematically screened in Toulouse on all blood donors with a manual technique on opaline plate using enzyme treated red cell tests (papain). 7,147 positive reactions were detected, out of 240,080 tests (2.98%). 1,954 (0,81%) were alloantibodies and 1,529 (0.64%) autoantibodies; 3.455 were false positive reactions and 209 were non identified antibodies. These figures are superimposed with those obtained with Groupamatic during the following years, thus pointing out the interest of this equipment.

Autoanalysis↗
PubMedDate not supplied

Natural history of insect sting allergy: the Rhode Island experience.

The frequency of insect sting allergy in a given population varies depending on the age group of the population and the type of criteria used (history, skin test or RAST). In a pediatric population with a mean age of 13 years (boy scouts), the frequency is 0.8% using history as the only criteria. With this same criteria in an adult population, other authors found the frequency to be higher, 3.3%. The difference is probably due to the prolonged exposure rate to insect stings in adults. Using skin test or RAST as the criteria, the frequency of sting allergy is much higher because of many false-positive reactions. With history alone, the frequency of sting reaction is similar in atopic and nonatopic populations. Sting-sensitive asthmatic patients usually have a severe reaction to a sting with the added symptom of acute bronchospasm. Our RAST studies to venoms revealed that false-positive reactions do occur; a higher frequency of positive reactions occurs within five years of the sting and cross-reactivity among Hymenoptera insects is common except for honey bee. Negative RAST may have more clinical validity than a positive RAST. Our past and present re-sting data reveal that a large percentage of initially sting-sensitive patients have no reaction on being re-stung. Our new study on untreated sting-sensitive patients revealed that 37% (7/19) had an improved response and 42% (8/19) had the same response on re-sting.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2005

Serological discrimination by indirect enzyme immunoassay between the antibody response to Brucella sp. and Yersinia enterocolitica O:9 in cattle and pigs.

A rapid, inexpensive and rugged serological test that distinguishes cattle and swine infected with Brucella sp. or Yersinia enterocolitica O:9 is described. The test protocol, which is an indirect enzyme immunoassay uses a high concentration of divalent cation chelating agents to minimize binding of Y. enterocolitica O:9 antibody to rough lipopolysaccharide antigen derived from B. abortus RB51. No false positive reactions were observed when testing 100 Canadian cattle and swine without any evidence of brucellosis. The assay detected 91.6% of cattle (n=155) and 93.5% (n=31) of swine infected with Brucella sp. Sera from 58 cattle and 38 swine exposed to Y. enterocolitica O:9 were negative while only 20 sera from 121 'false positive' reactors of unspecified origin gave low level positive reactions, eliminating 84% of the false positive reactions.

Animals↗
PubMed1985

False-positive guaiac testing with iodine.

The guaiac-impregnated test slide (Hemoccult) used in testing for occult blood in the stool gave a false-positive reaction in a trauma patient when a povidone-iodine antiseptic solution (Betadine) was used prior to the insertion of a urinary catheter. Laboratory testing using serial dilutions of povidone-iodine solutions indicates that as little as 0.005 mL of a 1:1,000 dilution will give a positive guaiac reaction. Separate testing confirms that the iodine component is responsible for this false-positive reaction. The mechanism is probably direct oxidation of the alpha-guaiaconic acid chromogen. Patients with perianal decubiti who are being treated with povidone-iodine solution, or those who have recently had a urinary catheter inserted, may need to have the area washed prior to guaiac testing. Antiseptics not containing iodine may be used in trauma patients to prevent false-positive guaiac reactions.

Adult↗
PubMed2002

Oxybuprocaine induces a false-positive response in immunochromatographic SAS Adeno Test.

OBJECTIVE: To investigate whether a solution of oxybuprocaine hydrochloride, 0.4%, results in a false-positive response in an immunochromatographic SAS Adeno Test. DESIGN: Experimental study. CONTROLS: Physiologic saline and 2% lidocaine. TESTING: Each chemical (100 microl) was diluted in a transport medium. Five drops (200 microl) of the resultant solution were dispensed into the round sample well of a test device. Fifteen samples were tested in each group. MAIN OUTCOME MEASURES: Ten minutes after the start of the test, a colored line in the "specimen" portion of the test membrane was visually read as positive or negative by a masked technician. RESULTS: No positive reaction was observed in the control groups (physiologic saline and lidocaine). A false-positive reaction was observed in six samples (33.3%) in the oxybuprocaine group. The positive rate was significantly higher in the oxybuprocaine group compared with those in control groups (P = 0.0062, Fisher's extract probability test). CONCLUSIONS: Oxybuprocaine may induce a false-positive reaction in an immunochromatographic SAS Adeno Test. We recommend the use of lidocaine, instead of oxybuprocaine, for local anesthesia in taking eye swabs from patients with suspected adenovirus infection.

Adenovirus Infections, Human↗
PubMed1995

[Suitability of monoclonal test sera for determination of blood group markers in positive direct Coombs test].

BACKGROUND: Monoclonal reagents of the IgM type allow to test some red blood cell antigens (K; Jka; Jkb) by the tube centrifugation method at room temperature, for the examination of which the indirect antiglobulin test was necessary in the past. This permits to test antigens also when the direct antiglobulin test is positive, provided the sera do not contain too much supplement. MATERIALS AND METHODS: We tested a choice of monoclonal reagents of different manufacturers (for the ABO system, A subgroups, the Rhesus, MN, Kell, Kidd and Lewis system) for their ability to examine antibody-coated erythrocytes. To recognize false-positive reactions of the reagents, erythrocytes without the particular antigen were coated with an incomplete antibody, and then the reagent was tested with these self-made Coombs control cells. RESULTS: We found no false-positive reactions for all tested anti-A, anti-B, anti-AB, and anti-A1 reagents. Some anti-C, anti-c, anti-E, anti-e and anti-N reagents showed weak false-positive reactions, some anti-H, anti-D, anti-K, anti-Jka, anti-Jkb, anti-Lea, anti-Leb and anti-M reagents stronger false-positive reactions.

Antibodies, Monoclonal↗
PubMed1975

Calf ligated intestinal segment test to detect enterotoxigenic Escherichia coli.

The ligated intestinal segment test in the young calf was utilized to establish the enterotoxigenicity of approximately 600 Escherichia coli isolates obtained from fecal specimens intestinal contents of calves with diarrheal disease. One hundred and fifty isolates were routinely tested in a single calf. There was little problem with false-positive reactions. False-negative reactions normally occurred only if the isolate was tested in the posterior 3 m of the small intestine. The ligated small intestine of the calf was distended by E. coli isolates of bovine, porcine, and human origin. Use of the calf ligated intestinal segment test is recommended to determine the enterotoxigenicity of E. coli isolates of bovine origin.

Animals↗
PubMed1979

Cell-mediated immune responses in cattle adult-vaccinated with Brucella abortus strain 19 and in cattle infected with Brucella abortus field strain.

Cell-mediated immune responses in cattle adult-vaccinated with Brucella abortus strain 19, cattle infected with B abortus field strain, and nonexposed cattle were studied by an in vitro lumphocyte-stimulation test (LST). Lymphocytes were prepared from peripheral bovine blood by the Ficoll-diatrizoate technique, and results were assayed for [3H]thymidine incorporation into DNA by liquid scintillation spectrometry. Serotests and bacteriologic isolation attempts were conducted simultaneously with LST. Lymphocytes from cattle infected with field strains had significantly (P = 0.01) higher specific lymphocyte-stimulation inexposed controls. The LST, the serum standard-tube agglutination test (STT), the Rivanol (RIV) test, and the complement-fixation (CF) test correctly classified cattle from which field strains and strain 19 of B abortus were isolated. The LST was negative in cattle vaccinated with B abortus strain 19 (nonshedding), but the three serotests had many false-positive reactions. The CF test had the least false-positive reaction, followed by the RIV test, and the STT was the least specific. Well before the three serotests became positive, the LST was positive in samples from some cattle during the incubation period of the infection. There was little or no correlation between cell-mediated immune responses (as measured by LST) and serum antibody responses (as measured by STT, RIV test, and CF test) in vaccinated but culture-negative cattle and in some nonvaccinated cattle during the incubation period.

Agglutination Tests↗