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PubMed1988

The case for patch test readings beyond day 2. Notes from the lost and found department.

Additional patch test readings taken after 2 days (48 hours) are valuable in distinguishing false-positive reactions, which may occur up to 22% of the time. Second readings taken on days 3 through 7 may detect an additional 34% positive reactivity. Those reactions, both lost (initially positive, later negative) and found (initially negative, later positive) by delayed readings, require clinical correlation for relevance as do the readings that persist at and beyond day 2 (positive at both readings).

Allergens↗
PubMed1988

Comparison of a monoclonal anti-HIV 1 gag solid phase with a polyclonal anti-HIV solid phase for detecting anti-HIV 1 in a competition ELISA.

An anti-HIV 1 competitive ELISA was developed using a monoclonal anti-HIV 1 gag to capture viral antigen to the solid phase. This format of assay was compared with a competitive ELISA where a polyclonal human anti-HIV 1 was used, to capture the viral antigen. Several benefits were observed using the monoclonal-antibody form of the assay. Firstly, less viral antigen was needed on solid phase to give an equivalent test in terms of positive and negative optical density 450 nm values. Secondly, a slight increase in sensitivity was also gained without any loss of specificity and finally, as a result of the murine nature of the antibody on the solid phase, no cross-reaction with the labelled human antibody in the test conjugate was observed. Such cross-linking has been observed with the polyclonal form of the assay and can lead to false-negative reactions.

AIDS-Related Complex↗
PubMed1997

Adverse reactions to fragrances. A clinical review.

This article reviews side-effects of fragrance materials present in cosmetics with emphasis on clinical aspects: epidemiology, types of adverse reactions, clinical picture, diagnostic procedures, and the sensitizers. Considering the ubiquitous occurrence of fragrance materials, the risk of side-effects is small. In absolute numbers, however, fragrance allergy is common, affecting approximately 1% of the general population. Although a detailed profile of patients sensitized to fragrances needs to be elucidated, common features of contact allergy are: axillary dermatitis, dermatitis of the face (including the eyelids) and neck, well-circumscribed patches in areas of "dabbing-on" perfumes (wrists, behind the ears) and (aggravation of) hand eczema. Depending on the degree of sensitivity, the severity of dermatitis may range from mild to severe with dissemination and even erythroderma. Airborne or "connubial" contact dermatitis should always be suspected. Other less frequent adverse reactions to fragrances are photocontact dermatitis, immediate contact reactions and pigmentary changes. The fragrance mix, although very useful for the detection of sensitive patients, both causes false-positive and false-negative reactions, and detects only 70% of perfume-allergic patients. Therefore, future research should be directed at increasing the sensitivity and the specificity of the mix. Relevance is said to be established in 50-65% of positive reactions, but accurate criteria are needed. Suggestions are made for large-scale investigation of several fragrances on the basis of literature data and frequency of use in cosmetics. The literature on adverse reactions to balsam of Peru (an indicator for fragrance sensitivity), essential oils (which currently appear to be used more in aromatherapy than in perfumery) and on fragrances used as flavours and spices in foods and beverages is not discussed in detail, but pertinent side-effects data are tabulated and relevant literature is provided.

Cosmetics↗
PubMed1980

Follow-up study of patients with contact dermatitis caused by chromates, nickel, and cobalt.

The patch test results from 1,000 patients tested with the ICDRG standard series are analyzed for positive reactions to potassium dichromate, nickel sulphate, and cobalt chloride. Nickel appears to be the most common sensitizer, especially among women, although false-negative reactions may occur if it is tested with a 2.5% concentration in yellow petrolatum. Chromate dermatitis is generally of occupational origin among men. It is also quite common among Belgian women, probably because of the widespread use of Javel (liquid bleach), containing sodium dichromate as a colouring and stabilizing agent. Positive patch test reactions to cobalt are generally accompanied by allergic reactions to nickel or chromate. Its role as a primary allergen, however, must never be overlooked. The relationship between these metals and hand and foot eczema is evaluated. The results of a follow-up questionnaire are given. More than 70% of the patients allergic to chromates or nickel continued to suffer from contact eczema after the diagnosis had been made and therapeutic measures taken.

Adult↗
PubMed2002

Tuberculin test measurement: variability due to the time of reading.

STUDY OBJECTIVES: It is recommended that the PPD Mantoux tuberculin test be read at 48 or 72 h. We have compared the measurements at these time points. DESIGN: A 10-tuberculin unit (TU) PPD Mantoux test was administered to 116 healthy subjects (76.7% with bacillus Calmette-Guérin scars). PARTICIPANTS: One hundred sixteen healthy adult volunteers were recruited (health service employees, 29 volunteers; general public, 87 volunteers). RESULTS: The measurements made at 72 h were significantly higher than those made at 48 h (median, 9.4 vs 4.95 mm, respectively; p = 0.017). In those subjects with induration at either or both time points (n = 69), the readings taken at 72 h were on average 1.7 mm (95% confidence interval, 0.4 to 3.0 mm) larger than those at 48 h. Using an induration of > 15 mm diameter to define a positive result, there were more positive test results at 72 h (36) compared to 48 h (28), with the results from 10 subjects (8.5%) changing because of the time of measurement. CONCLUSIONS: This study demonstrates that, in adults, the size of the 10-TU Mantoux reaction is significantly larger at 72 h compared to the reaction at 48 h. In clinical practice, tuberculin tests should be read at 72 h as negative tests at 48 h may be false results.

Adult↗
PubMed1981

Comparison of multiple puncture liquid tuberculin test with Mantoux test.

Two studies were performed to compare the disposable liquid tuberculin PPD 'Imotest' with the Mantoux test. While there was a tester effect in the first study indicating the need for accurate application of the imotest, the results of the second study showed that the two tests were comparable in selecting truly positive and negative tuberculin reactors. Results were compared both by conventional methods and by a method new to tuberculin testing, the maximum likelihood technique. This method gives a more accurate estimate of false reaction rates. A significant difference was found between reading at 48 and 72 h for both tests. The acceptability and ease of reading of the imotest, with a tuberculin selectivity comparable to the Mantoux method, make it a suitable alternative tuberculin test, especially for screening large populations.

False Negative Reactions↗
PubMed2003

Diagnostic testing patterns of natural Mycobacterium paratuberculosis infection in pygmy goats.

Thirteen pygmy goats (Capra hircus) from a herd naturally infected with Mycobacterium avium ss. paratuberculosis (MPTB) were monitored with 4 diagnostic assays for 2 to 15 mo. Cellular and humoral immune responses to the infection were assessed with assays of gamma interferon (IFNgamma), serum antibody [enzyme-linked immunosorbent assay (ELISA) and agar gel diffusion (AGID)], and radiometric fecal culture. Microscopic examination and radiometric culture of tissue from 12 sites were performed at necropsy. Goats were considered infected if MPTB was isolated from any tissue sample collected at necropsy. Mycobacterial isolates were confirmed as MPTB with an IS900 polymerase chain reaction assay. Ten goats whose antemortem tests indicated infection carried heavy organism burdens at necropsy, both within and beyond the gastrointestinal system. False-negative ELISA, AGID, and/or culture results were obtained in 5 of the 10 confirmed cases during the study period. In 3 goats with sporadic fecal shedding of MPTB or detectable IFNgamma response, or both, no abnormalities were detected at necropsy and no MPTB was isolated from the tissue samples; the antemortem fecal-culture and IFNgamma results were thus considered false-positive. Diagnosticians should be alert to the possibility of both false-positive and false-negative test results for Johne's disease in goats. False-positive fecal-culture results may occur when a high prevalence of infection exists in the herd and the premises are likely to be heavily contaminated. The diverse antemortem testing patterns seen in these goats underscore the importance of using varied diagnostic assays serially or in parallel to increase the likelihood of identifying all infected goats.

Animals↗
PubMed2002

Rh genotyping: avoiding false-negative and false-positive results among individuals of African ancestry.

High homology, variant alleles, and silent alleles have made the development of completely reliable genotyping assays for the RHD and RHC alleles difficult. An RHD pseudogene (RHDPsi) possessing a 37-bp insertion within exon 4 is common among serologically RhD-negative individuals of African descent and generates false-positive results in previously reported RhD genotyping assays. Genotyping RhC is problematic due to exon 2 homology between RHD and RHC; however, an RHC-specific 109-bp insertion within intron 2 has been reported useful for genotyping. Primers flanking the exon 4 insertion point were used for detection of RHD and RHDPsi among a total of 231 serotyped individuals: 134 African American, 85 Caucasian, and 12 RhD serotype-negative/genotype-positive, D-sensitized women. Primers flanking the RHC-specific intron 2 insertion were used to genotype 282 serotyped individuals (128 African American, 154 Caucasian) and were compared to RHC genotyping using the exon 1 RhC-specific nt48 cytosine polymorphism. Complete correlation was observed between genotyping with the RHDPsi primer pair and serotyping among 219 individuals and 10/12 previous RHD false-positive genotyping results were resolved. RHDPsi was detected in 19% (n = 4/21) of RhD seronegative African Americans and 4.4% (n = 5/113) of RhD seropositive African Americans. When using the 109-bp intron 2 insertion for genotyping of RHC, a 23.9% (n = 11/46) false-negative rate was observed among African American RhCc serotyped heterozygotes. Utilization of the exon 1 nt48 cytosine for indirect genotyping of RHC yielded a 7.2% (n = 4/55) and 56.3% (n = 45/80) false-positive rate among Rhcc Caucasians and African Americans, respectively. We conclude that these additional reactions, though not sufficient alone, can be useful supplements to existing Rh genotyping assays.

Alleles↗
PubMed1993

[Gel technique, a new sensitive method for the determination of erythrocyte antibodies. Advantages and disadvantages with introduction of a new method].

A gel technique for the detection of red blood cell antibodies was evaluated for antibody screening. A total of 1872 samples were screened using both gel technique and the conventional serological method, and later 18,292 samples were analysed by the gel technique and results confirmed by conventional methods. In both methods, Anti Human Globulin technique and enzyme technique were applied. The gel system gave false-negative results in 0.2% and false-positive results in 0.9% of the samples. The gel system was more sensitive than conventional technique in the detection of antibodies of clinical importance and less sensitive in detecting antibodies with low incidence of haemolytic transfusion reactions and haemolytic disease of the newborn. The gel technique seems suitable for laboratories with equipment for automatic pipetting of samples and reagents.

Antibodies↗
PubMed2004

An evaluation of the diagnostic value of different skin tests with egg in clinically egg-allergic children having atopic dermatitis.

Skin testing is a common diagnostic procedure in food allergy, but the final diagnosis of food allergy is based on the clinical response to food challenge. We studied the value of the skin prick-prick test (SPT), skin application food test (SAFT) and atopy patch test (APT) with fresh egg extract in diagnosing egg allergy. Ten clinically egg-allergic children with atopic dermatitis (AD; age 10 months to 8.4 yr, mean 3.4 yr) and 10 egg-tolerant children with and 10 without AD (age 2.4-11 yr, mean 5.5 yr) participated. In SAFT several false-negative reactions were seen, whereas all clinically egg-allergic children were positive in SPT and 40-60% in APT. In APT and in SPT false-positive reactions to egg were observed. In this study comprising a small number of patients including control subjects, neither SAFT nor APT with fresh whole egg extract were able to increase the diagnostic accuracy in detecting egg-allergic children with AD compared with SPT.

Child↗