The Lancet Weight Determines Wheal Diameter in Response to Skin Prick Testing with Histamine

BACKGROUND

Skin prick test (SPT) is a common test for diagnosing immunoglobulin E-mediated allergies. In clinical routine, technicalities, human errors or patient-related biases, occasionally results in suboptimal diagnosis of sensitization.

OBJECTIVE

Although not previously assessed qualitatively, lancet weight is hypothesized to be important when performing SPT to minimize the frequency of false positives, false negatives, and unwanted discomfort.

METHODS

Accurate weight-controlled SPT was performed on the volar forearms and backs of 20 healthy subjects. Four predetermined lancet weights were applied (25 g, 85 g, 135 g and 265 g) using two positive control histamine solutions (1 mg/mL and 10 mg/mL) and one negative control (saline). A total of 400 SPTs were conducted. The outcome parameters were: wheal size, neurogenic inflammation (measured by superficial blood perfusion), frequency of bleeding, and the lancet provoked pain response.

RESULTS

The mean wheal diameter increased significantly as higher weights were applied to the SPT lancet, e.g. from 3.2 ± 0.28 mm at 25 g to 5.4 ± 1.7 mm at 265 g (p<0.01). Similarly, the frequency of bleeding, the provoked pain, and the neurogenic inflammatory response increased significantly. At 265 g saline evoked two wheal responses (/160 pricks) below 3 mm.

CONCLUSION AND CLINICAL RELEVANCE

The applied weight of the lancet during the SPT-procedure is an important factor. Higher lancet weights precipitate significantly larger wheal reactions with potential diagnostic implications. This warrants additional research of the optimal lancet weight in relation to SPT-guidelines to improve the specificity and sensitivity of the procedure.

Comparison of Intradermal Dilutional Testing with the Multi-Test II Applicator in Testing for Mold Allergy

OBJECTIVES: To compare and correlate wheal size using the Multi-Test II applicator with the endpoint obtained by intradermal dilutional testing (IDT) for common mold allergens. To validate the safety and efficacy of modified quantitative testing (MQT) for determining immunotherapy starting doses.

STUDY DESIGN AND SETTING: Prospective study of 86 subjects with Multi-Test II and IDT for 6 common mold antigens.

RESULTS: There was 84% concordance between IDT results and the results expected from the MQT method. When IDT and MQT results differed, the MQT algorithm predicted a safer end-point for starting immunotherapy in all but 2 cases.

CONCLUSION: The correlation between Multi-Test II and IDT is not strong enough to infer IDT endpoint from Multi-Test II results for molds. MQT is nearly as effective as formal IDT in determining endpoint.

SIGNIFICANCE: MQT appears to be a safe method for determining starting doses for immunotherapy with fungal allergens.

Performances of an improved device for skin prick tests

Every day allergists deal with skin prick testing. Following a recent paper showing that the intravenous needle and the metal lancets are superior to the Stallerpoint® plastic lancet, the manufacturer has improved the device to reach better standards in terms of sensitivity, intra-patient reproducibility and inter-patient reproducibility, as demonstrated on 10 adult patients, comparing the results with skin tests performed with the intravenous needle. We evaluated the sensitivity of the device by calculating the ratio between the number of true-positive tests and the sum of true-positive and false-negative tests. To assess the reproducibility of the test, we calculated the interpatient and the intrapatient coefficient of variation between the mean diameters of the papules induced by the different techniques. The improved device shows performances similar to those obtained with the intravenous needle.

Tuberculin skin test and QuantiFERON in children

Until some time ago, the tuberculin skin test was the only available screening test for the diagnosis of tubercular infection. Now the new interferon-? release assay QuantiFERON-TB Gold shows promise of greater accuracy in the detection of Mycobacterium tuberculosis-infected subjects. The aim of our study was to evaluate the use of QuantiFERONTB Gold in children and to verify its agreement with the tuberculin skin test. A total of 27 children had a positive tuberculin skin test, 76 subjects were negative and the remaining 2 had a dubious Mantoux test. A positive QuantiFERONTB Gold result was obtained in 21 children while in 84 it was negative. No statistically significant difference was detected between the two assays, which showed a concordance of 90.57%. Our results demonstrated a good concordance between the tuberculin skin test and the interferon-? release assay, though the QuantiFERON-TB may have several advantages over the Mantoux test.

Comparison of five techniques of skin prick tests used routinely in Europe

BACKGROUND

Skin prick tests represent indispensable tools in allergy, even more than 30 years after their introduction in clinical practice.

OBJECTIVES

Few recent European studies have focused on this topic and we thus wanted to compare the instruments most often used today.

METHODS

Four instruments were investigated: the 23G intravenous (IV) needle, the ALK Lancet, the Stallergenes (STG) Prick Lancet and the Stallerpoint(®) (using two different methods). Sensitivity, reproducibility, and acceptability were evaluated. In 22 subjects, we calculated the sensitivity and reproducibility (both intra- and interpatient) of these methods by testing the positive control five times. In 50 subjects, we tested the single-blind acceptability of these same five techniques.

RESULTS

In terms of sensitivity, the IV needle (100%) and metal lancets (96% for the ALK Lancet and 98% for the STG Prick Lancet) were superior (P < 0.01) to the two Stallerpoint(®) methods (20% and 57%). Intrapatient reproducibility was 16.2%, 14.6%, 15.0%, 97.1% and 18.1%, respectively. The instruments that were best tolerated by the patients were the IV needle and the two metal lancets.

CONCLUSION

Metal needles and/or lancets are the tools of choice for skin prick testing.

Comparison of the Multi-Test II and ComforTen allergy skin test devices

The performance of different devices for percutaneous allergy skin testing may have statistically and clinically significant differences. We compared two multihead allergy skin testing devices: Multi-Test II (Lincoln Diagnostics, Decatur, IL) and ComforTen (Hollister-Stier Laboratories, Spokane, WA). Skin tests with glycerinated histamine (6 mg/mL base) and glycerinated saline were applied to 30 adults using Multi-Test II on the volar surface of one forearm and ComforTen on the opposite forearm. For each device, data were obtained from 150 histamine sites and 90 negative control sites. Defining a positive result using cutoff wheal sizes of either 5-mm versus 3-mm inclusive, respective results for Multi-Test II sensitivity were 97% versus 100% with specificity of 100% versus 97%, whereas corresponding ComforTen sensitivity increased from 26 to 82% with specificity of 100% versus 99%. For Multi-Test II versus ComforTen, histamine mean (SD) wheal sizes were 7.47 (1.72) mm versus 3.93 (1.59) mm (p = 0.00), mean coefficients of variation (CV) were 23.0% versus 40.5%, and pooled estimates of variance were 1.42 versus 1.29. Comparing results at different test head positions, there was no statistically significant variation in histamine wheal sizes with either device. Multi-Test II had notably lower CV, greater wheal size, and higher sensitivity but similar specificity to ComforTen. Consequently, Multi-Test II had superior performance at both 3- and 5-mm wheal cutoffs. Because ComforTen had a low sensitivity at the 3-mm and, particularly, at the 5-mm wheal cutoff, skin testing with this device might result in underdiagnosis of allergy using either cutoff.

Assessment of skin exposure to N,N-dimethylformamide and methyl ethylketone through chemical protective gloves and decontamination of gloves for reuse purposes

N,N-dimethylformamide (DMF) and methyl ethylketone (MEK) are the hazardous chemicals commonly used in the synthetic leather industries. Although chemical protective gloves provide adequate skin exposure protection to workers in these industries, there is currently no clear guideline or understanding with regard to the use duration of these gloves. In this study, the permeation of DMF/MEK mixture through neoprene gloves and the desorption of chemicals from contaminated gloves were conducted using the ASTM F739 cell. The acceptable use duration time of the gloves against DMF/MEK permeation was estimated by assuming a critical body burden of chemical exposure as a result of dermal absorption. In a re-exposure cycle of 5 days, decontamination of the gloves by aeration at 25°C was found to be inadequate in a reduction of breakthrough time as compared to a new unexposed glove. However, decontamination of the gloves by heating at 70 or 100°C showed that the protective coefficient of the exposed gloves had similar levels of resistance to DMF/MEK as that of new gloves. Implications of this study include an understanding of the use duration of neoprene gloves and proper decontamination of chemical protective gloves for reuse.

[Usefulness of skin prick test using bifurcated needle for the diagnosis of food allergy among infantile atopic dermatitis--second report. In the case of cow's milk allergy]

OBJECTIVE

We investigated the usefulness of skin prick test (SPT) using bifurcated needle (BN) for the diagnosis of cow's milk allergy (CMA) in early infancy.

SUBJECTS AND METHODS

Among atopic dermatitis infants with suspicion of food allergy who visited Sagamihara National hospital from January 2001 to April in 2005, 168 cases had received both SPT and IgE ImmunoCAP of CM (CM-IgE) at first visit. We analyzed results of SPT and CM-IgE, focused on infants with negative CM-IgE to examine the usefulness of SPT, and checked positive conversion of CM-IgE with aging.

RESULTS

Among 124 infants (73.8%) with negative CM-IgE, 34 infants (27.4%) showed positive SPT results. Forty two infants (33.6%) among the 124 cases were diagnosed as CMA by combination of elimination and provocation test, and 21 infants (50.0%) had positive SPT. In the follow up study of 39 negative CM-IgE cases with CMA, 21 CM-IgE (53.8%) turned positive later infantile period (mean CM-IgE: 4.2+/-4.8 Ua/ml at 9.3+/-5.3 months old).

CONCLUSIONS

SPT using BN seemed to be more useful than CM-IgE for the diagnosis of CMA in early infancy with AD. But, the sensitivity is lower than in the egg case.

[The comparison of reactions in skin prick test performed with the standardized lancet and the injection needle]

Achieving reproducible results with the skin prick test method depends on a certain amount of experience, the depth of skin penetration by the device which is used and reducing the number of false positive reactions caused by contamination of the device by allergen extract previously pricked. The aim of the study was to compare the results of SPT performed with "single puncture device" using lancet or injection needle with "multiple puncture device" using the same needle wiped in alcohol between pricks.

MATERIAL AND METHODS

Twenty adult patients with seasonal allergic rhinitis with known sensitivity to grass pollen allergen and ten control subjects entered the study. SPT were applied to the volar surface of both forearms on two separate visits during which fixed sequence of pricking histamine, allergen and saline solutions (Allergopharma, Reinbeck, Germany) was maintained. On the first visit new device was used for each prick: injection needles on one forearm and lancets on the other. On a second visit (after a wash-out period of 4 weeks) injection needle changed between each prick on one forearm was compared with using the same needle wiped in alcohol between pricks on the other forearm.

RESULTS

There was no statistical difference between the three tested methods for the size of wheel to histamine (p = 0.5), saline (p = 1) and allergen (p = 0.54) in group of SAR patients as well as for the size of wheel to histamine (p = 0.41) and saline (p = 1) in control subjects. Analysis of wheel diameters for histamine and allergen in group of SAR patients demonstrated comparable degrees of precision for all tested methods (CV%): there was no statistical difference between CV% achieved for the size of histamine (p = 0.73); as well as for allergen wheal (p = 0.32).

CONCLUSIONS

The results of SPT achieved by using only one injection needle rinsed in alcohol for multiple pricks seem to have similar quality, being more economical than standard techniques in which puncture device is changed between each test.

Use of the Reviscometer for measuring cosmetics-induced skin surface effects

BACKGROUND/PURPOSE

The Reviscometer RVM600 that measures resonance running time (RRT) has been shown to be inversely related to the skin stiffness. However, very few publications describe the use of this instrument for testing the effect of cosmetic products.

METHODS

Slight xerotic skin condition was induced by using an alkaline soap for 1 week. Skin has then been rehydrated with a lotion or further dehydrated and dried with sodium lauryl sulfate (SLS). Skin condition at the different stages of the study was evaluated by visual assessment for dryness and redness and by non-invasive methods (Corneometer, Cutometer, Reviscometer, Evaporimeter and squamometry).

RESULTS

All methods showed highly significant changes after the slight drying phase with the soap usage. They illustrated skin repair after lotion treatment and further skin impairment after SLS application. Nevertheless, the Reviscometer was able to better statistically discriminate between the treatments (water, lotion, SLS) than the Cutometer . Measurement of the RRT along the transversal axis of the forearms was the most sensitive for differentiating between normal and dry skin and between the treatments on the basis of skin mechanical properties.

CONCLUSION

The Reviscometer RVM600 is a sensitive instrument able to detect slight skin surface effect of cosmetics. Combined with published literature on the interpretation of RRT measurements on polymeric gel or in different skin conditions (elderly skin and photoaged skin), the Reviscometer looks to be a recommendable instrument to measure slight changes in SC stiffness/suppleness induced by cosmetic products.

Real-time Raman spectroscopy for non-invasive skin cancer detection - preliminary results

Raman spectroscopy is a non-invasive optical technique, which can assess molecular structures and conformations within biological tissue. The probability of Raman scattering is inherently low such that previous clinical applications of Raman spectroscopy have been limited by long data acquisition times. We have developed a rapid real-time Raman spectrometer system with measurement times of less than 1 second, paving the way for clinical application. In this presentation, we report preliminary clinical results for this real-time Raman system. To date 289 skin cancers and benign skin lesions have been measured. Using partial least squares regression and linear discriminant analysis to analyze the Raman spectra we found that skin cancers could be well differentiated from benign skin lesions (sensitivity 91% and specificity 75%) and malignant melanoma from benign pigmented lesions (sensitivity 97%, specificity 78%).

Optimization of the skin multiple analyte profile bioanalytical method for determination of skin biomarkers from D-Squame tape samples

BACKGROUND/PURPOSE

This work was performed to optimize extraction conditions for D-Squame tape skin samples for use in the skin multiple analyte profile (SkinMAP) method, a Linco Research Corporation bead-based assay for skin analytes. The experiments were designed to help identify sources of variability during extraction that may be amenable to further control.

METHODS

Two experimental designs were used to study factors influencing the extraction of skin samples from D-Squame tapes. Visually healthy skin samples were obtained from both female and male adult volar forearms. Factors studied in two experiments included: four surfactant (SDS) levels (0.02-0.2%), two buffer types [Citrate-phosphate buffered saline at pH 5.5, phosphate-buffered saline (PBS) at pH 7.4], two buffer volumes (1.0, 1.5 mL), two propylene glycol (PG) levels (0.1%, 1.0%), two extraction temperatures (7-10 degrees C, 22-30+ degrees C), two extraction times (30, 60 min), and location in sonication bath (two vectors). The response biomarkers were cortisol, fibronectin, human serum albumin, involucrin, keratin-6 and keratins 1, 10. Skin sampling sites were also evaluated as sources of variation.

RESULTS

There was no single set of extraction conditions in our experiments that maximized recovery of all the biomarkers. SDS level had the most consistently significant (P<0.05) and directional effects on biomarker recoveries. In general, higher SDS resulted in higher recovery of all biomarkers. There was less consistency and fewer significant results for the other extraction factors.

CONCLUSIONS

These data enable us to better manage SkinMAP studies and interpret their results. The use of 1.5 mL PBS containing 0.2% SDS and 0.5% PG with 30 min sonication at low (near 4 degrees C) temperature is optimal for the quantitation of a range of SkinMAP analytes. In order to protect researchers from obtaining inflated false positive rates, it is crucial to design such studies and analyze the data using appropriate statistical methodology, especially for those studies involving only a small number of subjects.

Comparison of intradermal dilutional testing, skin prick testing, and modified quantitative testing for common allergens

OBJECTIVES

To compare and correlate wheal size using the Multi-Test II applicator with the endpoint obtained by intradermal dilutional testing (IDT) for 5 common allergens. To examine the safety of modified quantitative testing (MQT) for determining immunotherapy starting doses.

STUDY DESIGN

Prospective comparative clinical study.

SUBJECTS AND METHODS

A total of 134 subjects were simultaneously skin tested for immediate hypersensitivity using the Multi-Test II device and IDT.

RESULTS

There was a 77% concordance between results from IDT and results from MQT. When there was a difference, MQT predicted a safer endpoint for starting immunotherapy in all but 2 cases.

CONCLUSION

Wheal size by SPT is predictive of endpoint by IDT. MQT is nearly as effective as formal IDT in determining endpoint.

SIGNIFICANCE

Modified quantitative testing appears to be a safe alternative to IDT for determining starting doses for immunotherapy.

Comparison of the Multi-Test II and Skintestor Omni allergy skin test devices

BACKGROUND

Different devices for percutaneous allergy skin testing have demonstrated statistically and clinically significant differences in performance characteristics.

OBJECTIVE

To compare 2 Food and Drug Administration-approved multihead allergy skin testing devices: Multi-Test II (Lincoln Diagnostics) and Skintestor Omni (Greer Laboratories).

METHODS

Skin tests with glycerinated histamine (6-mg/mL base) and glycerinated saline were applied to 31 adults using Multi-Test II on the volar surface of one forearm and Skintestor Omni on the opposite forearm.

RESULTS

Data were accumulated from 155 histamine sites and 93 negative control sites for each device. Using cutoff wheal sizes of 5 vs 3 mm inclusive to define a positive result, Multi-Test II sensitivity remained at 100%, but specificity increased from 74% to 97%, whereas Skintestor Omni sensitivity decreased from 94% to 87%, and specificity increased from 58% to 88%. For Multi-Test II vs Skintestor Omni, histamine mean (SD) wheal sizes were 9.23 (1.37) vs 7.74 (2.83) mm (P < .001), mean coefficients of variance were 14.8% vs 36.6%, and pooled estimates of variance were 0.642 vs 6.974. Multi-Test II produced similar histamine wheal sizes regardless of test head position used, whereas Skintestor Omni produced statistically significantly smaller wheals at certain test head positions.

CONCLUSIONS

Multi-Test II had higher sensitivity and specificity than Skintestor Omni and produced reproducible wheal sizes from all test head positions. Because some Skintestor Omni test head positions produced significantly smaller histamine wheal sizes, skin testing using this device might result in underdiagnosis of allergy.

Tape-stripping method in man: comparison of evaporimetric methods

BACKGROUND/PURPOSE

If the occlusion time of a closed chamber evaporimeter on the skin is too long, saturation might occur. We previously compared an open chamber and a closed chamber device on healthy volunteers. Comparable data on stripped skin with higher evaporation rates are not available. This study compares the sensitivity and correlation of open and closed chamber devices in a tape-stripping human model. The amount of tape removed SC was also quantified with a protein assay method.

METHODS

Ten healthy volunteers (six male and four female; seven Caucasians and three Asian; mean age 38+/-16) were enrolled. In a randomized manner, one forearm was measured by an open chamber device and the opposite by a closed chamber device. After recording baseline measurements, 20 strippings were taken on each test site with tape disks. Transepidermal water loss (TEWL) was measured at the end of 10 and 20 tape strippings at each test site. Stratum corneum (SC) aggregates in the strips was assayed.

RESULTS

The mean values obtained from two devices were similar after 10 trips and 20 strips. There was no statistically significant difference. The closed chamber device showed a slightly higher (but not significant) inter-individual coefficient of variation. SC aggregates in the strips were similar and without a statistically significant difference.

CONCLUSION

The study suggests that both devices might yield similar TEWL values on stripped human skin in vivo.

PPL and MDM skin test: New test kit is helpful in detecting immediate-type allergy to beta-lactams

BACKGROUND

The diagnosis of PPL (major determinant) and MDM (minor determinant) sensitization as relevant allergens in beta-lactam allergy has been recently hampered by withdrawal from the market of formerly available test kits. We investigated a new PPL/MDM test kit in the work-up of beta-lactam allergy.

PATIENTS AND METHODS

15 patients with history of beta-lactam allergy were investigated for specific IgE and received patch, skin prick (SPT) and intracutaneous tests (ICT; immediate and late readings) using the relevant beta-lactams. In addition the new test kit was used for parallel SPT and ICT.

RESULTS

14 women and 1 man (16-73 years) with immediate (n = 7), delayed (n = 7) or unclear (n = 1) reactions to beta-lactams 8-300 months previously (penicillin G/V n = 3, aminopenicillins n = 7, cephalosporins n = 4, unknown n = 2) were tested. In patients with immediate type reactions, n = 2 had specific IgE, n = 4 reacted to the new test kit (n = 3 MDM, all of whom reacted exclusively to this test, n = 1 PPL). Two patients with non-immediate reactions reacted to other beta-lactams.

CONCLUSIONS

Our data show that the new test kit may be helpful in detecting patients with immediate type allergy to beta-lactams. Without this test, in those three patients reacting exclusively to MDM, and oral provocation test would have been necessary to clarify their allergy. Data from larger groups of patients are needed to determine the sensitivity and specificity of this test kit.

Delayed hypersensitivity skin testing in the Thai adult population

OBJECTIVE

The present study was carried out in healthy Thai subjects to determine the types and concentrations of standard antigens used in delayed-type hypersensitivity (DTH) skin testing as an evaluation of cell-mediated immunity.

MATERIAL AND METHOD

One hundred subjects were tested with three antigens including tuberculin (purified protein derivative), tetanus toxoid, 1:10 and 1:100 dilutions, and Candida albicans, 1:10 and 1:100 dilutions.

RESULTS

We found that 92% of the subjects responded to tuberculin and/or tetanus toxoid at a 1:10 dilution, 77% responded to tetanus toxoid at a 1:10 dilution, and 35% responded to a 1:100 dilution. There was only one subject who responded to Candida albicans at a 1:10 dilution, and none to a 1:100 dilution. The size of tuberculin reactions varied from 5 mm to over 20 mm without any evidence of active tuberculosis.

CONCLUSION

Tuberculin and tetanus toxoid at a 1:10 dilution are probably sufficient to be used in DTH skin testing to evaluate T-cell function.

A comparison of two single-headed and two multi-headed allergen skin test devices

Given the potential differences in performance of skin test devices, the purpose of this study was to prospectively assess the performance of two single-headed and two multiheaded devices for allergy skin testing in terms of wheal size, sensitivity, specificity, intradevice variability, and pain level. Two single-headed devices (Greer Pick, Duotip-Test) and two multiheaded devices (Multi-Test II, OMNI) were tested in 15 subjects in a prospective partially blind fashion looking at wheal reactions and pain using histamine and glycerol-saline on the arms and back. Differences among devices in wheal size and pain were noted. Sensitivity, specificity, and intradevice variability were calculated. Differences between corner and interior heads in multiheaded devices were analyzed. No significant differences were observed in wheal size between Greer Pick (7.1+/-1.4 mm) and Duotip-Test (7.2+/-1.6 mm). Multiheaded devices were significantly different in wheal size compared with each other and to the single-headed devices (Multi-Test II, 5.4+/-1.7 mm; OMNI, 3.3+/-1.2 mm). Single-headed devices were more sensitive (100% each, 95% CI of 92-100%) than the multiheaded devices. Multi-Test II was significantly more sensitive (83%, 95% CI of 78-87%) than OMNI (57%, 95% CI of 51-62%). There was significant intradevice variability for the multiheaded devices with corner heads being significantly more sensitive than interior heads. Specificities for all devices were equally good (-97%). Pain was greater for multiheaded devices than single-headed devices but was generally mild. In conclusion, this study supports the idea that single-headed devices may be more sensitive and consistent than multiheaded devices. Multi-Test II is more sensitive than OMNI. In multiheaded devices, corner heads are more sensitive than interior heads.

Adequacies of skin puncture for evaluating biochemical and hematological blood parameters in athletes

OBJECTIVE

The authors tested the effect of blood sampling (skin versus venous puncture) on some biochemical and hematological blood parameters in athletes to answer whether skin puncture could be used as a substitute for venous puncture.

DESIGN

Comparative study of 2 methods of blood samples collection.

SETTING

The blood was collected in the same athletes at 3 different moments of the preparatory training phase.

PARTICIPANTS

Fourteen male indoor soccer players (22 +/- 1 years old) and 7 female handball players (18 +/- 1 years old) participated.

MAIN OUTCOME MEASUREMENT

Blood was collected in heparin and K3EDTA by Vacutainer BD or Microvette Sarstedt system for biochemical and hematological analyses, respectively.

RESULTS

There were no significant statistical differences between the 2 methods for the values of creatine kinase, urea, creatinine, lymphocytes, and platelets. The other hematological analyzes and uric acid exhibited significant higher values in skin blood, although they were all within the normal expected range. A high degree of correlation was observed between the 2 techniques for all parameters.

CONCLUSIONS

Skin puncture is a reliable, easy, accurate, and less invasive sampling method for assessing hematological and some biochemical parameters in athletes, respecting that blood samples should always be obtained from the same site, especially in follow-up studies.

Skin testing for immediate hypersensitivity to betalactams: comparison between two commercial kits

INTRODUCTION

Skin testing with major and minor determinants of benzylpenicillin is the recommended standard practice to evaluate subjects with immediate hypersensitivity to betalactams. The withdrawal of these products from the market has set us back to the early days, before the introduction of reagents for in vivo testing.

OBJECTIVES

To compare a recently released kit of benzylpenicillin conjugated to poly-l-lysine (PPL) and minor determinants mixture (MDM) with the previously existing kit in a positive control group of subjects sensitized to major and/or minor determinants of benzylpenicillin.

METHODS

Skin tests with both kits were made in a group of positive subjects previously diagnosed with immediate hypersensitivity to penicillins and with positive results to PPL and/or MDM and in a negative control group. Radioallergosorbent test (RAST) inhibition assays with a pool of sera and individual samples were carried out to compare the inhibition capacity of PPL and MDM of both kits.

RESULTS

Of 22 cases selected from our historical group, 14 were positive: eight to PPL, three to MDM and three to both. These results were equivalent for both kits. RAST inhibition studies showed similar potencies in the inhibition of PPL and MDM.

CONCLUSIONS

Both tests show similar results in terms of RAST inhibition assays and skin tests sensitivity and specificity in the groups selected. The new assay can be used for the same purpose and indications as the previous test.

Skin capacitance imaging and corneosurfametry. A comparative assessment of the impact of surfactants on stratum corneum

Silicon image sensor (SIS) technology was recently introduced as an innovative tool (SkinChip, L'Oréal) providing sensitive imaging of the skin capacitance. This method can detect discrete focal variations in skin surface hydration, and thus early discrete manifestations of skin irritation induced by surfactants. In the present in vivo study, 2 neat and diluted shampoos, and 5% and 10% sodium laurylsulfate solutions were tested on human skin. Each surfactant solution was gently rubbed on the skin using wet hair wicks mimicking the casual use of a shampoo on the scalp. Clinical and SIS evaluations were carried out. In addition, the same products were tested using the ex vivo corneosurfametry bioassay performed on human stratum corneum (SC) harvested by cyanoacrylate skin surface strippings. The colourimetric index of mildness (CIM) was measured on these samples. The product reactivity with the SC was recognized by darker skin capacitance images, and by both lowered SkinChip-generated values and lowered CIM values. The extent in changes varied according to the nature of the test products and their concentrations. The SkinChip image changes likely corresponded to the acute surfactant-induced water swelling of the corneocytes. Skin capacitance imaging and corneosurfametry allow to disclose discrete surfactant-induced alterations of corneocytes.

The effect of montelukast (10mg daily) and loratadine (10mg daily) on wheal, flare and itching reactions in skin prick tests

Antileukotriene agents are widely used for the treatment of allergic conditions including bronchial asthma and allergic rhinitis. The influence of montelukast on skin reactivity has not been clearly evaluated. The aim of this study was to determine the effect of montelukast on wheal, flare and itching in skin prick tests (SPTs).

METHODS

Fifteen atopic patients (5 women and 10 men) with average age 28.04 (SD+/-8.24) were tested with histamine, codeine, negative control solution and allergen extract (grasses). Montelukast (10mg), loratadine (10mg) or placebo were given to the volunteers for 5 days in a double-blind manner, followed by SPT, with 14 days of wash-out period.

RESULTS

There was no differences in wheal, flare and itching (p=0.205; 0.086 and 0.069, respectively, Wilcoxon rank-sum test) between SPT performed after placebo and wash-out period. The analysis revealed a statistically significant suppression of wheal and flare by loratadine (p<0.05 for all tested solutions). Pre-treatment with montelukast did not influence wheal size (p=0.099, 0.21, 0.066 for histamine, codeine and allergens, respectively), but significantly reduced flare (p=0.005; 0.003; 0.02 for histamine, codeine and allergens, respectively). We found a significant suppression of itching produced by montelukast (p=0.02) and loratadine (p=0.03) as compared to placebo (p=0.068 vs. wash out).

CONCLUSIONS

Our data show a tendency to suppressive effect of montelukast on flare and itching but not on wheal which is basic for SPT interpretation. We conclude that found suppression have little impact on clinical effectiveness of SPT as a diagnostic tool.

Improvements in skin-testing technique

Allergy skin testing is the primary modality used in the diagnosis of allergic diseases and guides development of treatment and avoidance plans. The goal of the Allergist is to skin test the appropriate population with a device and technique that minimizes pain while maximizing sensitivity and specificity. The debate involving the use of intradermal versus skin-prick testing in the diagnosis of aeroallergy has been long lasting. Past and present medical literature will be reviewed, establishing the lack of diagnostic use of intradermal testing in the setting of aeroallergy. New skin devices continue to be developed with a trend toward production of multidevices. Performance characteristics of various skin test devices will be reviewed with an emphasis on sensitivity, specificity, and variability of skin-prick testing devices. Significant statistical differences exist between all devices tested and reported in the literature. Whether these statistical differences equate to clinical differences is not known. With this review the practicing allergist should carefully evaluate multiple different devices and choose a device that suits their practice needs. In addition, allergists must ensure that technicians are sufficiently trained on the correct use of their device and should conduct continuing education to ensure that proper skin testing techniques are being used in their practice. Finally, the use of skin testing in pediatrics will be reviewed with a focus on safety. Care should be taken when skin testing infants < or = 6 months of age, especially in the setting of eczema and a family history of atopy.

Comparison of test devices for skin prick testing

BACKGROUND

Allergy skin testing guides developing avoidance plans and writing an immunotherapy prescription. The goal for the allergist is to apply allergen skin testing to the appropriate patient population by using a device that minimizes both false-negative and false-positive findings while minimizing patient discomfort. New skin testing devices continue to be developed with a trend toward production of multiheaded devices. Data on the performance of these devices in a head-to-head prospective fashion are limited.

OBJECTIVE

Our goal was to study 8 commonly used devices to compare their performance in a head-to-head fashion.

METHODS

In a prospective, double-blind fashion, the performance of 8 skin test devices was evaluated. Devices were tested with histamine and saline on both the arms and back of each subject. Devices were rotated over 4 testing sessions, at least a week apart, so each device was tested in each anatomic testing location. Performance elements examined included wheal, flare, pain, sensitivity, specificity, and intradevice variability.

RESULTS

We found significant differences in all areas of device performance among all devices examined. Multiheaded devices also demonstrated significant intradevice variability and were more painful than single devices. Furthermore, multiheaded devices had larger reactions on the back, whereas single devices had larger reactions on the arms.

CONCLUSION

Statistically significant differences exist among all devices tested. Providers should consider this data when choosing a device that suits their practice setting and ensure that technicians are sufficiently trained on the correct use of that device.

[Comparison of two lancets in the skin prick test]

BACKGROUND

The skin prick test is used to diagnose the allergic sensitization. Its results depend upon several factors, such as the lancet type. In Cuba, the most frequently used are: ALK lancet and blood lancet.

OBJECTIVE

To compare these two lancets regarding the size of the wheal, precision, sensitivity and specificity of the skin prick test and, finally, the preference of the patients to one of them.

PATIENTS AND METHODS

The study was performed in 60 allergic patients, aged 15-50 years, seen at the allergy service of Hospital Universitario Clínico Quirúrgico General Calixto García. The skin prick test was performed on the forearm of all patients included, using both lancet types. A negative control (diluent solution) was applied, together with a 54.3 mmol/L histamine solution in five replicates.

RESULTS

The mean size of skin reaction to histamine was 6 mm, using a 1 mm single peak lancet (ALK), size was 6.5 mm when using blood lancet (significant difference p < 0.05). Precision, sensitivity and specificity of ALK lancet were 9.7, 100 and 100%, respectively. On the other hand, the respective values for blood lancet were 15.9, 96 and 87%. Of those studied, 27% presented mild pain and 3% moderate pain using the ALK lancet; while 25% showed mild pain and 10% moderate pain using the blood lancet.

CONCLUSION

The ALK lancet showed more precision, sensitivity and specificity and it was preferred by the patients.

Provocation testing in polymorphic light eruption using fluorescent ultraviolet (UV) A and UVB lamps

BACKGROUND

Provocation testing is frequently performed during investigation of patients with suspected polymorphic light eruption (PLE). Techniques are not standardized between centres.

OBJECTIVES

We sought to evaluate the efficacy of different fluorescent ultraviolet (UV) radiation lamps for provocation testing in PLE.

METHODS

We analysed results in 68 patients referred consecutively for phototesting in whom a diagnosis of PLE seemed likely based on clinical history. Patients' case notes were reviewed and responses recorded to provocation testing on forearm skin over three consecutive days using broadband UVA, narrowband and broadband UVB lamps.

RESULTS

A positive papular response to broadband UVA exposure was seen in 38 patients [56%, estimated 95% population confidence interval (CI) 43-67.9]. Thirty-four patients (50%) had a positive papular response to narrowband UVB exposure (95% CI 37.6-62.4). The probability of a positive provocation test following irradiation with both lamps was 80.9% (95% CI 69.5-89.4). From April 1999, 34 patients also had provocation testing with broadband UVB. Although six patients (18%) had a positive papular response, they all showed a positive response to one or both of the other lamp types.

CONCLUSIONS

Provocation testing with fluorescent UVA and UVB lamps is a cheap and readily available method that can be used as a diagnostic aid to investigate patients with suspected PLE. Using both broadband UVA and narrowband UVB lamps for testing increases the likelihood of confirming the diagnosis than if either lamp is used alone.

Comparison of Multi-Test II skin prick testing to intradermal dilutional testing

OBJECTIVES/HYPOTHESIS

Intradermal dilutional testing (IDT) has been considered more sensitive than prick testing for detecting low-level allergies. Multi-Test II is one of the most sensitive and reproducible prick testing methods available. This study compares Multi-Test II prick testing with IDT.

DESIGN

Retrospective chart review and data analysis on patients who had allergy testing with both Multi-Test II and IDT.

SETTING

Outpatient allergy clinic in the otolaryngology department of an academic tertiary care medical center.

POPULATION

Forty adult patients had complete allergy testing with both Multi-Test II and IDT for a standard panel of twelve antigens between January 2002 and April 2002.

INTERVENTION

Analysis and comparison of test results on Multi-Test II and IDT for each antigen separately and across all antigen tests together.

RESULTS

Forty patients had complete testing for all antigens during the time period for the study. Six of these patients did not react to the positive control on Multi-Test II and were eliminated from the main analysis. Of the 34 patients included in the main analysis, all were positive for at least one antigen on IDT; one half (17/34) were negative for all antigens on Multi-Test II. A significantly greater number of patients were positive on IDT than Multi-Test II for all antigens except dog (P < 0.05). There was a statistically significant correlation between IDT endpoint and Multi-Test II score for several antigens (P < 0.05). Of 408 total antigen tests performed, 339 (83.1%) were negative on Multi-Test II. Of these 339 negative Multi-Test II tests, 148 (43.7%) were negative on IDT and 191 (56.3%) were positive on IDT; 174/339 (51.3%) had an IDT endpoint of 2 or 3 and 17/339 (5.0%) had an IDT endpoint > or = 4. A significantly greater number of antigen tests were positive on IDT than on Multi-Test II (P < 0.001). The overall Spearman correlation coefficient between IDT endpoint and Multi-Test II score was 0.370 (P < 0.001).

CONCLUSION

Patients were more likely to have a positive test on IDT than on Multi-Test II. IDT therefore may be a more sensitive testing technique for inhalant allergies than Multi-Test II prick testing. In addition, Multi-Test II score may not be a good predictor of IDT endpoint. Although a statistically significant correlation is demonstrated between Multi-Test II score and IDT endpoint, the correlation coefficient is low enough that clinical application may not always be safe or appropriate. The clinical significance of positive IDT results in the presence of negative Multi-Test II results is not known.

The results of skin prick testing in patients with allergic rhinitis: a comparison between a multiple lancet device and a single lancet

Skin prick testing (SPT) is widely used in the assessment of allergic disorders. Different SPT techniques are widely used. The aim of this study was to compare the response to SPT using a multiple lancet device (MLD) with the results of a single lancet (SL). Fifty patients with allergic rhinitis were included in this study. Initially, SPT was performed by a SL technique. After one week SPT was repeated using the MLD on all patients. The patients were tested with a panel containing 19 specific allergens including grass pollen, tree pollen, house dust mites, weed pollen allergen extracts, histamine and a negative control. The skin responses were recorded after 15 minutes for each device by measuring the diameter of the wheal and the erythema. The skin wheal responses for grass pollen, tree pollen, weed pollen and house dust mite allergen extracts obtained using the SL were generally significantly larger than those using the MLD. The comparison between the MLD and the SL methods revealed that SPT was positive with SL and negative with MLD in 176 tests (15.3%), and on the contrary SPT was positive with MLD and negative with SL in only 13 tests (1%). In conclusion, we claim that SPT using SL shows a higher degree of sensitivity and reproducibility.

Can we evaluate electrodermal testing?

Electrodermal testing (ED testing) is an acupuncture-based approach and was developed to refine homeopathic prescriptions. It is currently being used to advise patients about their "allergies". The evidence for its use in "allergy testing" is limited and often misrepresented. This article addresses the research and clinical issues involved in investigating the reliability and validity of various ED testing machines.

[The PIPET or Patient Individual Plate Easy Test]

The fresh outbreak of allergies and especially that increasingly early for food or even for new pneumallergens (sensitization already in utero) pushes us to test increasingly various and many allergens in children. The insufficiency of compliance of certain children to allergic skin tests encouraged us to seek new diagnostic methods. In our office we developed a new method of diagnosis by multipuncture, individualized and easily adaptable to each child. It is about a fast and reproductible prick-test which avoids stains and smudges due to the application of drops directly on the skin. It makes it possible to initially place easily all the tests on a plate (PIPET or Patient Individual Plate Easy Test) then on the skin by a multipuncture method. The tests can even already be prepared in the days which precede, provided that the plates are put in the fridge, with the name of the patient and the allergens used, for memory. It is about a rigorous test, reliable and careful, easy to carry out even in the most difficult children.

A comparison of two skin test methodologies and allergens from two different manufacturers

BACKGROUND

Skin prick tests (SPTs) are a frequently used method for evaluation of atopy. A variety of standard allergen preparations are available, together with a number of different methods of application.

OBJECTIVE

The objective of this study was to compare SPT reactivity 1) using Soluprick SQ allergens (ALK Allergologisk Laboratorium A/S, Hørsholm, Denmark) and Bayer allergens [Bayer Corporation, West Haven, CT], and 2) using two common methods of application, a standard prick lancet and a Quintest, both produced by Bayer.

METHODS

SPTs were undertaken on 22 adult volunteers (mean age 40 years, 17 female, 5 male). Wheal size was recorded as mean diameters (mm) and area (mm2).

RESULTS

Bayer allergens produced larger mean diameters and areas to dust mites than ALK allergens, with the differences significant when allergens were applied with the lancet. There was a tendency for the ALK cat allergen to produce larger reactions than the Bayer product. The method of application also influenced the wheal size, with the lancet producing significantly larger mean diameters than the Quintest for the histamine and allergens from both manufacturers, except the ALK cat allergen. There were similar differences between methods of application for reactions measured as an area.

CONCLUSIONS

SPTs that use different allergens or different methods of application will not provide comparable assessments of atopy.

Murine auricular transepidermal water loss -- a novel approach for evaluating irritant skin reaction in mice

The standard method for evaluating contact allergy in mice is the ear swelling technique. However, in experimental irritant contact dermatitis, the epidermal barrier disruption, that represents a predominant effect of irritants, cannot be assayed by this

METHOD

An appropriate method to evaluate barrier disruption is the measurement of transepidermal water loss (TEWL) but to date this has so far been possible only on the trunk of hairless or shaved mice. We therefore developed a new technique to measure the TEWL of mice ears (murine auricular TEWL: MATEWL). After patch testing with irritants and allergens, respectively, we found that the ear swelling method is most suitable for evaluating allergic skin reactions, whereas MATEWL is most appropriate for evaluating irritant skin reactions.

Is electrodermal testing as effective as skin prick tests for diagnosing allergies? A double blind, randomised block design study

OBJECTIVE

To evaluate whether electrodermal testing for environmental allergies can distinguish between volunteers who had previously reacted positively on skin prick tests for allergy to house dust mite or cat dander and volunteers who had reacted negatively to both allergens.

DESIGN

Double blind, randomised block design.

SETTING

A general practice in southern England.

PARTICIPANTS

15 volunteers who had a positive result and 15 volunteers who had a negative result on a previous skin prick test for allergy to house dust mite or cat dander.

INTERVENTION

Each participant was tested with 6 items by each of 3 operators of the Vegatest electrodermal testing device in 3 separate sessions (a total of 54 tests per participant). For each participant the 54 items comprised 18 samples each of house dust mite, cat dander, and distilled water, though these were randomly allocated among the operators in each session. A research nurse sat with the participant and operator in all sessions to ensure blinding and adherence to the protocol and to record the outcome of each test.

OUTCOME

The presence or absence of an allergy according to the standard protocol for electrodermal testing.

RESULTS

All the non-atopic participants completed all 3 testing sessions (810 individual tests); 774 (95.5%) of the individual tests conducted on the atopic participants complied with the testing protocol. The results of the electrodermal tests did not correlate with those of the skin prick tests. Electrodermal testing could not distinguish between atopic and non-atopic participants. No operator of the Vegatest device was better than any other, and no single participant's atopic status was consistently correctly diagnosed.

CONCLUSION

Electrodermal testing cannot be used to diagnose environmental allergies.

Evaluation of three methods for using the Duotip-Test device for skin testing

The sensitivity and precision of rotation, prick and puncture methods of using the Duotip-Test for epicutaneous allergy skin testing were evaluated. Forty-one volunteers who had not taken any antihistamines within the previous two weeks were recruited. The mean age was 21.6 years (range 18 to 25 years). Histamine hydrochloride 1 mg/ml and 50% glycerol saline were used as positive and negative controls, respectively. Each method of testing was performed in triplicate on the volar surface of both forearms. Wheal and flare were measured 15 minutes later. Rotation, prick and puncture methods produced histamine mean wheal diameter +/- standard deviation of 6.61 +/- 0.87 mm, 3.86 +/- 1.03 mm, and 3.00 +/- 0.65 mm, respectively (p < 0.01). The coefficient of variation of rotation method was 13.13%. It was the only method that gave coefficient of variation lower than 20%. False negative and false positive proportions of rotation method using a 4 mm criterion for positive reaction were 1.5% and 0.75%, respectively. Rotation method was well accepted by the volunteers although it was ranked highest in pain. We concluded that the rotation method of using Duotip-Test is a highly reliable technique for skin testing.

A blinded, multi-center evaluation of two commercial in vitro tests for latex-specific IgE antibodies

PURPOSE

To compare the diagnostic value of two commercial in vitro tests for the detection of latex-specific IgE antibodies.

METHODS

Serum samples were collected from latex-allergic and nonlatex-allergic individuals. Persons were classified as latex allergic if they had a positive clinical history and a positive skin prick test with a latex extract. Persons with no latex-related symptoms and negative skin tests were classified as nonlatex allergic. The serum samples were tested in a blinded fashion by a laboratory using the CAP (Pharmacia-Upjohn) and AlaSTAT (Diagnostic Products Company) assays. Values of 0.35 kA U/L or greater were considered positive in both tests.

RESULTS

The 143 sera studied came from 83-latex allergic and 60 nonallergic persons. The in vitro tests were found to have sensitivities of 79.5% and 73.8%, and specificities of 90.2% and 91.7%, for CAP and AlaSTAT, respectively. The positive predictive values were 91.7% and 92.5%, while the negative predictive values were 76.4% and 71.4% for the CAP and AlaSTAT, respectively.

CONCLUSION

In individuals classified by the combination of clinical history and skin test results, both the Pharmacia CAP and the DPC AlaSTAT demonstrated acceptable sensitivities, specificities, and predictive values for detection of antilatex IgE antibodies. These findings suggest that both assays can be useful adjuncts to the diagnosis of latex allergy.

Comparison of the Quintest to the lancet in allergic skin testing

Many skin testing devices have been commercially available over recent years, but use has been limited because of significantly greater costs of such devices. Therefore, the lancet continues to be the most widely used skin testing device in Australia. This study compared performance of another multitest device, the Bayer Quintest to the Becton Dickinson Microlance. Nineteen atopic volunteers were skin tested using histamine dihydrochloride 10 mg/ml, glycerosaline and eight allergens. In 190 tests, 6 discrepancies between the Quintest and Microlance occurred. The Microlance produced slightly larger wheals than the Quintest, reaching statistical significance in 3 allergens. We found the Quintest comparable to the Microlance in concordance of positive and negative allergen responses and in wheal size. The Quintest had higher acceptability to both participants and staff for comfort, ease of use and safety. The Quintest's major advantage is the ability to rapidly screen large numbers of subjects, especially during clinical trials. The major limitation is it's cost.

[A new device for allergen skin testing]

We have made a new device for allergen skin testing, which can be used easily. It consists of two parts. One, several gears are fixed on a board in a row, and when one gear goes round, other gears also go round simultaneously. A disposable needle is attached to each gear. A semi-spherical hole is made in the lower surface of a disposable needle, and a sharp needle is fixed in, but not at the centre of the hole. The other, small tanks are arranged in a row at the same distance as the gears. When the disposable needles are inserted to the tanks filled with allergen extract, it is hold in a semi-spherical hole by surface tension. The allergen extracts go intradermally, when the needles move semi-circular on a human skin. We performed skin tests to 23 patients with this device, and got satisfactory results as screening tests.

Reproducibility of skin prick test results in epidemiologic studies: a comparison of two devices

The reproducibility of skin prick tests under field conditions is essential for comparing prevalences between centers in epidemiologic multicenter studies. This study aimed to evaluate and compare the reproducibility of two widely used skin prick test devices: the Multi-Test and the ALK lancet. The subjects were 28 children, aged 6-14 years, with known sensitivities to Dermatophagoides pteronyssinus (D. pter.). Both devices were applied to each subject on two occasions, 1 week apart, by different, randomly assigned fieldworkers, using histamine, negative control, and the D. pter. allergen extract. For all three tested solutions, mean wheal sizes were larger for the Multi-Test than for the ALK lancet. The coefficient of variation for histamine was 21.8% for the Multi-Test and 17.3% for the ALK lancet. The coefficients of variation for the allergen D. pter. amounted to 47.4% for the Multi-Test and to 24.6% for the ALK lancet. The percentage of concordant test results was 92.6% for the Multi-Test and 100.0% for the ALK lancet for a cutoff point of wheal size equal to or greater than 1 mm. The results of this study suggest that the single ALK lancet performs slightly better than the Multi-Test device with respect to reproducibility under conditions of epidemiologic field studies.

Evaluation of devices for skin prick testing

BACKGROUND

Previous comparisons of devices for percutaneous skin testing have revealed statistically and clinically significant differences, from one device to another, in the size of reactions to histamine and allergen extracts and at negative control sites.

OBJECTIVE

The objective of this study was to compare the performance of several skin test devices which are either new, modified, or used with a modified technique.

METHODS

Twenty subjects were tested five to eight times with each of the devices both to glycerol-saline and to 10 mg/ml histamine base. The devices tested were the MultiTest II, Duo Tip-Test (prick and scarification), Quintest, DermaPik (prick and scarification), and small pox needle.

RESULTS

There were highly significant differences among the devices for the size of the reaction to histamine (mean wheal diameter 4.28 to 8.59 mm, p < 0.0001), the standard errors of the wheals to histamine (0.82 to 1.45 mm, p < 0.05) and in the mean wheal size with glycerol-saline (0.00 to 2.48 mm, p < 0.0001).

CONCLUSIONS

Devices for performing skin prick testing vary greatly in several characteristics, including the size of reactions at both positive and negative test sites. Each skin test technician should be tested with the device used in that skin testing laboratory to establish criteria for positive and negative tests.

Solar urticaria. A report of 25 cases and difficulties in phototesting

BACKGROUND

Solar urticaria is a rare photosensitive disease, and its differential diagnosis with respect to polymorphous light eruption is sometimes difficult. We report our experience with 25 cases of solar urticaria and discuss the pitfalls in phototesting such patients.

OBSERVATION

The most important locations in this patient series are the V of the neck and the arms, which are similar to those of polymorphous light eruption. In all of the patients, however, the lesions appeared within 30 minutes of sun exposure or phototesting and disappeared within 24 hours. Notably, 12 (48%) of the patients had a history of atopy. Phototesting helps confirm the diagnosis, but, in some patients, this was difficult.

CONCLUSIONS

A negative phototest result from a single light source does not necessarily exclude a diagnosis of solar urticaria. In patients in whom phototesting elicits negative reactions, other light sources should be used, and, if the phototest result is still negative, a provocative test with natural sunlight should be done. Histamine1-receptor antihistamines are a useful first-line therapy, although more severely affected persons may require prophylactic courses of phototherapy or photochemotherapy. The main problem is maintenance treatment.

Electrical impedance for quantification and classification of experimental skin reactions

BACKGROUND

Pathophysiologic events in biological tissue are characterized by a shift of the electrical impedance spectra of the tissue under study.

OBJECTIVE

To discuss studies on experimental skin reactions with an improved impedance spectrometer. The instrumentation is related to noninvasive techniques based on other physical principles.

METHODS

The results from studies on patients with allergic contact reactions (n = 8), prick tests (n = 10), and irritant contact reactions (benzalkonium chloride [n = 14], sodium lauryl sulfate [n = 12], and nonanoic acid [n = 14]), and an appropriate number of controls are reviewed.

RESULTS

Results show statistically significant changes of the impedance parameters when compared with relevant controls, at different types of experimental cutaneous reactions, both allergic and irritant type. Each reaction type had a specific impedance index pattern.

CONCLUSIONS

Current data indicate that the improved impedance technique offers a possible noninvasive alternative for characterization and perhaps differentiation, not only between the skin responses induced by either an allergen or an irritant, but also a capability to distinguish responses induced by chemically different irritants. The assumption that the impedance method is capable to distinguish allergic from irritant contact reactions has not been proven yet in direct comparative studies.

Bevel-down superior to bevel-up in intradermal skin testing

BACKGROUND

Intradermal skin testing is one of the most widely used procedures in the diagnosis of hypersensitivity diseases in vivo. It is critical to perform the test accurately and expediently. Yet, there are few articles describing its detailed technique or proficiency available.

OBJECTIVES

To identify the better method for intradermal testing between the bevel-up and bevel-down techniques.

METHODS

Three inexperienced testers performed intradermal injections using both methods. Four sets of paired trails each consisting of ten injections were applied randomly, alternating between the same volunteer subject's contralateral arms. Duration to complete ten injections was measured. Numbers of injection sites that bled, that squirted into the air, and failed to form a bleb were counted. The overall comfort level was determined.

RESULTS

The time to complete the injections by bevel-up and by bevel-down methods were 165.5 +/- 31.3 and 152.5 +/- 27.4 seconds, respectively (P < .015). The number of injection sites that bled was higher in the bevel-up method, particularily on trial one (P < .001). Completion rate of successful bleb formation in bevel-down was 27.3 as compared with 23.3 in bevel-up method (P = .013). The comfort level was higher with the bevel-down than the bevel-up method (P = .0001).

CONCLUSION

The bevel-down method of intradermal testing is superior to the bevel-up method.