Diagnostic testing in the evaluation of food allergy

Comparison of commercial allergen extract with various milk products of skin prick tests in diagnosing cow's milk protein allergy

Introduction: In this study, we aimed to solve the incompatibilities between the skin prick test (SPT) result and the clinical picture encountered among patients. Thus, we used various milk products (raw, ultrahigh temperature [UHT], and pasteurized cow's milk) with commercial milk allergen extract in patients we think may have cow's milk protein allergy (CMPA) and made a comparison among the milk types. Methods: This study was conducted retrospectively between February 1, 2019, to June 1, 2019, at a pediatric allergy polyclinic of the university training/research hospital. A pair of 79 individuals, as control and patient groups, ages between 1 month and 21 years who were presented with a suspicion of CMPA and defined with SPT and/or allergen-specific immunoglobulin E (IgE) levels were included in the study. Allergen-specific IgE tests (specific IgE cow's milk, β-lactoglobulin, α-lactalbumin, casein) were evaluated. SPT was performed with fresh/raw, UHT, and pasteurized (daily) cow's milk besides the standard used commercial extract. Results: In the group included in the study and defined as IgE-mediated CMPA, 52.9% of the 79 patients were boys (n = 46), 47.1% were girls (n = 33), and the median age was 6 months (5.0-8.0 months). In the group of specific IgE cow's milk reaction that was sought, frequency and wheal (induration) size of SPT reaction to fresh/raw milk was also found to be statistically significant between positive- and negative-reaction groups, not detected against other milk products. The area under the curve for the diagnostic value of fresh milk was 93.1%. For the cutoff value of 2.50 mm, 88.1% sensitivity and 90.8% specificity were determined. In the group of specific IgE β-lactoglobulin reaction searched, there was a statistically significant difference in the frequency of SPT positivity and wheal size against UHT, fresh, and daily/pasteurized milk between positive and negative reaction groups. When the correlations of the mean induration axis in the tests were examined, it was found that, among raw milk, daily milk, cow's milk allergen extract, and UHT milk, a strong positive correlation was also statistically significant. Conclusion: The positivity that could not be detected with SPT when using allergen extract in a patient with positive specific IgE cow's milk result in the clinic can be detected with SPT made with fresh (raw) milk, which can be an alternative. In addition, specific IgE β-lactoglobulin seems to be the most compatible with the SPT wheal size (induration) of other milk types rather than extract. Comparative studies of SPT allergen extracts and various milk types used in the diagnosis of CMPA are very scarce in the literature, and more studies are needed on this subject.

An evaluation of the factors affecting the clinical and laboratory findings, prognosis, and treatment response in children with chronic urticaria

Chronic urticaria (CU) is a rare disease in childhood, and studies in children are limited. In this study, the aim was to investigate the clinical and laboratory findings and demographic characteristics of children with CU and to determine the factors affecting prognosis. The study included 141 patients aged 0-18 years who were diagnosed with CU in the pediatric allergy outpatient clinic between January 1, 2013, and December 31, 2018. Risk factors related to prognosis were investigated by comparing the duration of CU and treatment response with clinical and etiological features. IBM SPSS version 24 was used for statistical analyses. In the study group, the female/male ratio was 69/55, and the median age at first visit was 9.5 years (min:1, max:17). Among patients, 63 (44.5%) had an accompanying atopic disease, and 23 (16.3%) had chronic disease. Of the patients, 124 (88%) had chronic spontaneous urticaria, and 17 patients (12%) had chronic inducible urticaria (CIU). Of those with CIU, 72.2% had symptomatic dermographism, 16.7% had cholinergic urticaria, and 11.1% had cold urticaria. After the evaluations, the most common pathological findings in our patients were intestinal parasitosis (n = 14), anemia (n = 10), and urinary tract infection (n = 8). The median total duration of urticaria was 47 weeks (min:8, max:284). The duration of urticaria was longer in patients with atopy (p < 0.05), and the group that went into remission with standard-dose antihistamine was the group with highest eosinophil count (p = 0.022). In most children with CU, the underlying cause/disease cannot be determined. In our study, treatable triggers were found in some of the patients. Therefore, it is appropriate for each patient to be evaluated with selected laboratory tests after detailed history and physical examination.

Hair and saliva test fails to identify allergies in dogs

OBJECTIVES

Several companies offer saliva and/or hair tests for food and environmental allergies in companion animals, but provide no validation of test accuracy. We examined one such hair and saliva allergy test to determine whether it could reliably differentiate between a normal dog and an allergic dog, and to examine test repeatability.

MATERIALS AND METHODS

Ten fur and saliva samples were submitted from a known allergic dog and a normal, non-allergic dog. Five fake fur samples and water were also submitted to determine whether the test could differentiate between a real dog and toy animal. The company performed testing for 128 food and environmental allergens. Statistical analyses were performed to determine whether the response distribution differed significantly between dogs, using the Pearson chi-square coefficient, as well as to determine test-retest reliability by calculating Cohen's kappa for each allergen.

RESULTS

The distribution of test results from samples obtained from allergic, non-allergic or fake dogs was not different from that expected due to random chance. Test-retest reproducibility was poor to slight.

CLINICAL SIGNIFICANCE

Hair and saliva testing should not be used to diagnose allergies and is not a substitute for veterinary-directed allergy evaluation and diagnostics.

Cow's milk allergy: Evaluating tolerance through skin-prick test

Objective:

To evaluate the wheal diameter in allergy skin-prick tests (SPT) with cow's milk extract (CM) comparing tolerant and persistent patients.

Method:

A retrospective cohort study involving database analysis of children with diagnosis of cow's milk protein allergy (CMPA) mediated by immunoglobulin E in a specialized outpatient clinic that regularly performed SPT between January 2000 and July 2015. Patients were allocated into two groups: tolerant or persistent. Comparisons were made at diagnosis and over time between tolerant and persistent patients using Fisher's, Mann-Whitney or Wilcoxon tests and significance level at 5%.

Results:

After applying inclusion and exclusion criteria, the sample includes 44 patients (29 tolerant and 15 who persisted with CMPA). In the tolerant group, the medians of SPT were: 6 mm at diagnosis and 2 mm at the development of tolerance; a significant difference (p<0.0001) was found. In the persistent group, the median SPT at diagnosis was 7 mm, while in the last SPT it was 5 mm, with no statistical difference (p=0.173). The comparison of medians in the last SPT between groups was significant (p=0.001), with a reduction greater than 50% in SPT in the tolerant group.

Conclusion:

Serial SPTs were useful for diagnosis, and a decrease higher than 50% in diameter can indicate the moment to perform oral food challenge (OFC) tests, helping to detect tolerance in CMPA.

The relationship between a specific IgE level and asthma outcomes: results from the 2005-2006 National Health and Nutrition Examination Survey

BACKGROUND

Allergen exposure is associated with increased specific IgE (sIgE), and allergen exposure plus sensitization is predictive of asthma outcomes. However, it is not known if sIgE is predictive of asthma outcomes in the absence of exposure data.

OBJECTIVE

To investigate whether IgE to indoor allergens is predictive of and has a dose-response relationship with asthma emergency department (ED) visits and wheeze.

METHODS

In the 2005-2006 National Health and Nutrition Examination Survey, 351 children and 390 adults reported current asthma. Continuous sIgE to 9 indoor allergens were considered. Asthma morbidity in the past year was measured by wheezing. Health care utilization was defined as any asthma ED visits in the past year.

RESULTS

Analyses were adjusted for race, age, education, poverty index ratio and (in adults) tobacco use. In children, ED visits were associated with cockroach (odds ratio [OR] 1.5 [95% CI, 1.1-2 .1), rat (OR 1.9 [95% CI, 1.2-2.8]), and Aspergillus (OR 1.6 [95% CI, 1.001-2.60]). Continuous Aspergillus (OR 1.5 [95% CI, 1.04-2.1), Alternaria (OR 1.4 [95% CI, 1.1-1.6]), and total IgE (OR 1.2 [95% CI, 1.1-1.4]) were associated with wheeze in children. Adult ED visits were associated with sIgE for dust mites (Dermatophagoides pteronyssinus OR 1.6 [95% CI, 1.3-2.1]; Dermatophagoides farinae OR 1.6 [95% CI, 1.3-1.9]), total IgE (OR 1.4 [95% CI, 1.04- 1.9]), and the sum of sIgEs (OR 1.6 [95% CI, 1.2-2.2]).

CONCLUSIONS

Sensitization to particular indoor environmental allergens was found to be a risk factor for wheeze and asthma ED visits. These outcomes increased as the concentration of sIgE to these allergens increased.

Molecular diagnosis of peanut allergy

Peanut allergy prevalence has increased in developed countries over the last few decades in the frame of the allergy epidemics, currently affecting 1-2% of children. While less frequent in developing countries, its prevalence is rising as these countries adopt a more westernized lifestyle. There is no curative treatment for peanut allergy at present so patient management relies on peanut avoidance, which requires an accurate diagnosis. Recent progress in peanut allergy diagnosis was made with the introduction of component resolved diagnosis that allows the assessment of IgE specific to individual peanut allergens. Component-resolved diagnosis needs to be interpreted in the context of clinical data but overall increases the diagnostic accuracy, as described in the typical cases that we present. Novel diagnostic tools have been proposed recently, such as the basophil activation test, mRNA expression and resonance magnetic evaluation of biomarkers.