The CC2D2B is a novel genetic modifier of the clinical phenotype in patients with hereditary angioedema due to C1 inhibitor deficiency.

Hereditary angioedema due to C1 inhibitor deficiency (HAE-C1-INH) is a rare genetic disorder caused by pathogenic variants in the SERPING1 gene and characterised by swelling and a highly variable clinical phenotype. We aimed to identify novel modifying genetic factors predisposing to the clinical symptoms. We performed whole exome sequencing (WES) and comprehensive bioinformatic analysis in symptomatic and asymptomatic (three duos) family members with HAE-C1-INH. Selected variants identified using WES (present in all asymptomatic and absent in symptomatic patients) were determined using Sanger sequencing. We included 88 clinically well-characterised HAE-C1-INH patients from south-eastern Europe (nine asymptomatic) from 42 unrelated families. We identified 39 variants in 23 genes (ANKRD36C, ARGFX, CC2D2B, IL5RA, IRF2BP2, LGR6, MRPL45, MUC3A, NPIPA1, NRG1, OR5M1, OR5M3, OR5M10, OR8U3, PLCL1, PRSS3, PSKH2, PTPRA, RTP4, SEZ6, SLC25A5, VWA3A, and ZNF790). We selected variants in CC2D2B and PLCL1, which were analysed using Sanger sequencing in the entire group of HAE-C1-INH. We found significant differences in the frequencies of the CC2D2B c.190A>G (rs17383738) variant between symptomatic and asymptomatic patients, where heterozygotes were more common in asymptomatic HAE-C1-INH patients in comparison to symptomatic patients (55 % vs 23%; P = 0.049, OR = 4.24, 95% CI 1.07-14.69). Our study identified novel genetic factors that modify the clinical variability of HAE-C1-INH. We further demonstrated, in a large cohort, the importance of the CC2D2B gene as a disease-modifying factor. Based on linkage disequilibrium analysis, the CCNJ and ZNF518A genes might also be involved in the clinical variability of HAE-C1-INH.

Blood Transcriptomics Identifies Multiple Gene Expression Pathways Associated with the Clinical Efficacy of Hymenoptera Venom Immunotherapy.

Allergen-specific venom immunotherapy (VIT) is a well-established therapy for Hymenoptera venom allergy (HVA). However, the precise mechanism underlying its clinical effect remains uncertain. Our study aimed to identify the molecular mechanisms associated with VIT efficiency. We prospectively included 19 patients with HVA undergoing VIT (sampled before the beginning of VIT, after reaching the maintenance dose, one year after finishing VIT, and after a sting challenge) and 9 healthy controls. RNA sequencing of whole blood was performed on an Illumina sequencing platform. Longitudinal transcriptomic profiling revealed the importance of the inhibition of the NFκB pathway and the downregulation of DUX4 transcripts for the early protection and induction of tolerance after finishing VIT. Furthermore, successful treatment was associated with inhibiting Th2, Th17, and macrophage alternative signalling pathways in synergy with the inhibition of the PPAR pathway and further silencing of the Th2 response. The immune system became activated when reaching the maintenance dose and was suppressed after finishing VIT. Finally, successful VIT restores the immune system's balance to a state similar to that of healthy individuals. Our results underline the important role of the inhibition of four pathways in the clinical effect of VIT: Th2, Th17, NFκB, and macrophage signalling. Two biomarkers specific for successful VIT, regardless of the time of sampling, were C4BPA and RPS10-NUDT3 and should be further tested as potential biomarkers.

High burden of clonal mast cell disorders and hereditary α-tryptasemia in patients who need Hymenoptera venom immunotherapy.

BACKGROUND: In patients who require venom immunotherapy (VIT), there is a need to identify underlying mast cell (MC) disorders since these may affect the risk and severity of future sting reactions and the long-term effectiveness of VIT. METHODS: 1319 individuals with Hymenoptera venom allergy (HVA) who needed VIT from referral centers in Slovenia, Austria, Croatia, and Poland underwent examination for KIT p.D816V in peripheral blood leukocytes (PBL) using a highly sensitive PCR test and tryptase genotyping by digital droplet PCR. We also included 183 control individuals with large local reactions (LLRs) to Hymenoptera stings and with asymptomatic sensitization to Hymenoptera venoms. RESULTS: 285 of 1319 individuals recommended for VIT (21.6%) were positive for KIT p.D816V in PBL, preferably those who present with severe reaction (33.9% [n = 207 of 610] with Ring-Messmer grade 3-4 vs. 11% [n = 78 of 709] with Grade 1-2; p < .0001), whereas only 1.3% (n = 2 of 152) of controls with LLR and none with asymptomatic sensitization (n = 31) had KIT p.D816V. KIT p.D816V allelic burden was higher in those with severe reaction (median 0.018% [n = 207] in Grade 3-4 vs. 0.001% [n = 78] in Grade 1-2; p < .0001), and the majority had normal baseline serum tryptase levels (69% [n = 196 of 285]). All KIT p.D816V-positive individuals (n = 41) who underwent bone marrow (BM) biopsy were found to have underlying clonal diseases, principally BM mastocytosis. HαT was also associated with severe HVA and symptoms (p < .01), and remarkably, 31.0% (n = 31 of 100) were found to have concomitant KIT p.D816V. Concomitant HαT and KIT p.D816V showed an additive effect, and having both was associated with the highest risk for severe HVA, even higher than having either HαT or KIT p.D816V alone (OR = 3.8; p < .01). CONCLUSIONS: By employing prospective universal tryptase genotyping and examination for KIT p.D816V in PBL in large HVA populations, we have demonstrated a high burden of clonal MC disorders and HαT in patients who require VIT.

Impairment of EQ-5D-5L Domains According to Allergic Rhinitis and Asthma Control: A MASK-air Real-World Study.

BACKGROUND: EQ-5D-5L (EuroQOL, 5 Domains, 5 Levels) is a widely used health-related quality-of-life instrument, comprising 5 domains. However, it is not known how each domain is impacted by rhinitis or asthma control. OBJECTIVE: To assess the association between rhinitis or asthma control and the different EQ-5D-5L domains using data from the MASK-air mHealth app. METHODS: In this cross-sectional study, we assessed data from all MASK-air users (2015-2021; 24 countries). For the levels of each EQ-5D-5L domain, we assessed rhinitis and asthma visual analog scales (VASs) and the combined symptom-medication score (CSMS). We built ordinal multivariable models assessing the adjusted association between VAS/CSMS values and the levels of each EQ-5D-5L domain. Finally, we compared EQ-5D-5L data from users with rhinitis and self-reported asthma with data from users with rhinitis alone. RESULTS: We assessed 5354 days from 3092 users. We observed an association between worse control of rhinitis or asthma (higher VASs and CSMS) and worse EQ-5D-5L levels. In multivariable models, all VASs and the CSMS were associated with higher levels of pain/discomfort and daily activities. For anxiety/depression, the association was mostly observed for rhinitis-related tools (VAS nose, VAS global, and CSMS), although the presence of self-reported asthma was also associated with worse anxiety/depression. Worse mobility ("walking around") was particularly associated with VAS asthma and with the presence of asthma. CONCLUSIONS: A worse rhinitis control and a worse asthma control are associated with higher EQ-5D-5L levels, particularly regarding pain/discomfort and activity impairment. Worse rhinitis control is associated with worse anxiety/depression, and poor asthma control with worse mobility.

Increased Focus on Internal Body Sensations Is Associated with Higher Patient-Perceived Severity of Allergic Rhinitis.

BACKGROUND: Monitoring allergic rhinitis (AR) severity with objective biomarkers is important for the clinical management of patients as well as for research purposes. The most commonly used tool for the assessment of AR severity is the Total Nasal Symptom Score (TNSS). Objective biomarkers like skin prick test size or specific IgE levels do not correlate with TNSS. OBJECTIVE: We hypothesize that the psychological factors are the missing link between patient-perceived severity of AR and objective biomarkers. METHOD: Thirty-nine patients (median age: 34 years; 21 [54%] female) with grass pollen-related AR were enrolled in our study. Patients allergic for perennial allergens and allergens with potentially overlapping seasons including cypress, ash/olive, plane, and nettle families were excluded. Patient-reported outcomes included symptom score, medication scores, combined score, and Juniper Mini Rhinitis Quality of Life Questionnaire (minRQLQ). Psychometric evaluation was performed using 5 different psychological questionnaires that measure 13 different psychological factors. RESULTS: There was a significant correlation between the symptom score and private body consciousness (r = 0.50, p = 0.001) and neuroticism (R = 0.41 and p = 0.01). There was also a statistically significant correlation between the combined score and private body consciousness (r = 0.49 and p = 0.001) and with perceiving and understanding emotions (r = 0.34 and p = 0.04). The miniRQLQ score had a positive correlation with private body consciousness (r = 0.55 and p = 0.002) and observing (r = 0.42 and p = 0.02). CONCLUSIONS: Our data suggest that patients who are more aware of internal stimuli, as well as those who are highly self-conscious and somatically concerned tend to experience more severe AR symptoms.

Length of Hospital Stay and Survival of Hospitalized COVID-19 Patients During the Second Wave of the Pandemic: A Single Centre Retrospective Study from Slovenia.

Background: As of writing, there are no publications pertaining to the prediction of COVID-19-related outcomes and length of stay in patients from Slovene hospitals. Objectives: To evaluate the length of regular ward and ICU stays and assess the survival of COVID-19 patients to develop better prediction models to forecast hospital capacity and staffing demands in possible further pandemic peaks. Methods: In this retrospective, single-site study we analysed the length of stay and survival of all patients, hospitalized due to the novel coronavirus (COVID-19) at the peak of the second wave, between November 18th 2020 and January 27th 2021 at the University Clinic Golnik, Slovenia. Results: Out of 407 included patients, 59% were male. The median length of stay on regular wards was 7.5 (IQR 5-13) days, and the median ICU length of stay was 6 (IQR 4-11) days. Age, male sex, and ICU stay were significantly associated with a higher risk of death. The probability of dying in 21 days at the regular ward was 14.4% (95% CI [10.9-18%]) and at the ICU it was 43.6% (95% CI [19.3-51.8%]). Conclusion: The survival of COVID-19 is strongly affected by age, sex, and the fact that a patient had to be admitted to ICU, while the length of hospital bed occupancy is very similar across different demographic groups. Knowing the length of stay and admission rate to ICU is important for proper planning of resources during an epidemic.

The Allergic Rhinitis and Its Impact on Asthma (ARIA) Approach of Value-Added Medicines: As-Needed Treatment in Allergic Rhinitis.

Drug repurposing is a major field of value-added medicine. It involves investigating and evaluating existing drugs for new therapeutic purposes that address unmet healthcare needs. Several unmet needs in allergic rhinitis could be improved by drug repurposing. This could be game-changing for disease management. Current medications for allergic rhinitis are centered on continuous long-term treatment, and medication registration is based on randomized controlled trials carried out for a minimum of 14 days with adherence of 70% or greater. A new way of treating allergic rhinitis is to propose as-needed treatment depending on symptoms, rather than classical continuous treatment. This rostrum will discuss existing clinical trials on as-needed treatment for allergic rhinitis and real-world data obtained by the mobile health app MASK-air, which focuses on digitally-enabled, patient-centered care pathways.

Academic Productivity of Young People With Allergic Rhinitis: A MASK-air Study.

BACKGROUND: Several studies have suggested an impact of allergic rhinitis on academic productivity. However, large studies with real-world data (RWD) are not available. OBJECTIVE: To use RWD to assess the impact of allergic rhinitis on academic performance (measured through a visual analog scale [VAS] education and the Work Productivity and Activity Impairment Questionnaire plus Classroom Impairment Questions: Allergy Specific [WPAI+CIQ:AS] questionnaire), and to identify factors associated with the impact of allergic rhinitis on academic performance. METHODS: We assessed data from the MASK-air mHealth app of users aged 13 to 29 years with allergic rhinitis. We assessed the correlation between variables measuring the impact of allergies on academic performance (VAS education, WPAI+CIQ:AS impact of allergy symptoms on academic performance, and WPAI+CIQ:AS percentage of education hours lost due to allergies) and other variables. In addition, we identified factors associated with the impact of allergic symptoms on academic productivity through multivariable mixed models. RESULTS: A total of 13,454 days (from 1970 patients) were studied. VAS education was strongly correlated with the WPAI+CIQ:AS impact of allergy symptoms on academic productivity (Spearman correlation coefficient = 0.71 [95% confidence interval (CI) = 0.58; 0.80]), VAS global allergy symptoms (0.70 [95% CI = 0.68; 0.71]), and VAS nose (0.66 [95% CI = 0.65; 0.68]). In multivariable regression models, immunotherapy showed a strong negative association with VAS education (regression coefficient = -2.32 [95% CI = -4.04; -0.59]). Poor rhinitis control, measured by the combined symptom-medication score, was associated with worse VAS education (regression coefficient = 0.88 [95% CI = 0.88; 0.92]), higher impact on academic productivity (regression coefficient = 0.69 [95% CI = 0.49; 0.90]), and higher percentage of missed education hours due to allergy (regression coefficient = 0.44 [95% CI = 0.25; 0.63]). CONCLUSION: Allergy symptoms and worse rhinitis control are associated with worse academic productivity, whereas immunotherapy is associated with higher productivity.

Patch testing with the European baseline series and 10 added allergens: Single-centre study of 748 patients.

BACKGROUND: The European baseline series (EBS) of contact allergens is subject to change. An allergen is considered for inclusion when routine patch testing of patients with suspected contact dermatitis results in ≥0.5% prevalence rate. OBJECTIVES: We aimed to determine the frequency of sensitizations to 30 EBS allergens and 10 locally added allergens. Additionally, we assessed the strength and evolution of reactions to all tested allergens and co-reactivity of additional allergens. METHODS: Patch testing with our baseline series of 40 allergens was done in 748 consecutive adults. Tests were applied to the upper back and removed by patients after 48 h. Readings were done on Day 3 (D3) and D6 or D7 (D6/7). Positive reactions fulfilled the criteria of at least one plus (+) reaction. A retrospective analysis was done. RESULTS: Eight allergens not listed in the EBS had ≥0.5% prevalence rate (i.e., cocamidopropyl betaine, thiomersal, disperse blue mix 106/124, 2-bromo-2-nitropropane-1,3-diol, diazolidinyl urea, propylene glycol, Compositae mix II and dexamethasone-21-phosphate), and 16.6% of positive reactions would have been missed without D6/7 readings. CONCLUSION: We propose further studies to evaluate whether cocamidopropyl betaine, disperse blue mix 106/124, 2-bromo-2-nitropropane-1,3-diol, diazolidinyl urea and Compositae mix II need to be added to the EBS.

Usefulness of rapid antigen testing for SARS-CoV-2 screening of healthcare workers: a pilot study.

BACKGROUND: Identification of infected healthcare workers (HCWs) is an important step in severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) transmission control. Rapid antigen tests (RATs) are considered an important addition to molecular tests in diagnosing coronavirus disease 2019 (COVID-19), mainly because of their fast turnaround time, easier analytical procedure and lower price. However, real-life studies on the usefulness of such testing for screening of HCWs are limited. METHODS: Physicians, nurses and hospital attendants currently working at the University Clinic of Respiratory and Allergic Diseases Golnik were invited to participate in the pilot study. Nasopharyngeal swabs were obtained three times per week for two consecutive weeks and tested with a point-of-care RAT and reverse transcription polymerase chain reaction (RT-PCR). Serum samples were obtained at the beginning of the study and 2 weeks after the last swab was collected to evaluate the serological status. RESULTS: A total of 191 nasopharyngeal swabs from 36 HCWs were obtained. None of the samples tested was positive for the presence of SARS-CoV-2 antigen, whereas two HCWs tested positive on RT-PCR. Of these, one HCW had a newly identified SARS-CoV-2 infection, whereas RT-PCR probably detected a previous but recent infection in the other HCW. CONCLUSION: Based on the results of this pilot study, it is unlikely that RAT will reliably detect novel SARS-CoV-2 infections among asymptomatic HCWs despite serial sampling. Although RT-PCR-based screening of HCWs may not be feasible due to high sample volume, molecular methods may identify SARS-CoV-2-infected HCWs already during the presymptomatic stage. Trial registration number NCT04716088, 19.1.2021, retrospectively registered.

Robust Saliva-Based RNA Extraction-Free One-Step Nucleic Acid Amplification Test for Mass SARS-CoV-2 Monitoring.

Early diagnosis with rapid detection of the virus plays a key role in preventing the spread of infection and in treating patients effectively. In order to address the need for a straightforward detection of SARS-CoV-2 infection and assessment of viral spread, we developed rapid, sensitive, extraction-free one-step reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and reverse transcription loop-mediated isothermal amplification (RT-LAMP) tests for detecting SARS-CoV-2 in saliva. We analyzed over 700 matched pairs of saliva and nasopharyngeal swab (NSB) specimens from asymptomatic and symptomatic individuals. Saliva, as either an oral cavity swab or passive drool, was collected in an RNA stabilization buffer. The stabilized saliva specimens were heat-treated and directly analyzed without RNA extraction. The diagnostic sensitivity of saliva-based RT-qPCR was at least 95% in individuals with subclinical infection and outperformed RT-LAMP, which had at least 70% sensitivity when compared to NSBs analyzed with a clinical RT-qPCR test. The diagnostic sensitivity for passive drool saliva was higher than that of oral cavity swab specimens (95% and 87%, respectively). A rapid, sensitive one-step extraction-free RT-qPCR test for detecting SARS-CoV-2 in passive drool saliva is operationally simple and can be easily implemented using existing testing sites, thus allowing high-throughput, rapid, and repeated testing of large populations. Furthermore, saliva testing is adequate to detect individuals in an asymptomatic screening program and can help improve voluntary screening compliance for those individuals averse to various forms of nasal collections.

Hymenoptera Venom Immunotherapy: Immune Mechanisms of Induced Protection and Tolerance.

Hymenoptera venom allergy is one of the most severe allergic diseases, with a considerable prevalence of anaphylactic reaction, making it potentially lethal. In this review, we provide an overview of the current knowledge and recent findings in understanding induced immune mechanisms during different phases of venom immunotherapy. We focus on protection mechanisms that occur early, during the build-up phase, and on the immune tolerance, which occurs later, during and after Hymenoptera venom immunotherapy. The short-term protection seems to be established by the early desensitization of mast cells and basophils, which plays a crucial role in preventing anaphylaxis during the build-up phase of treatment. The early generation of blocking IgG antibodies seems to be one of the main reasons for the lower activation of effector cells. Long-term tolerance is reached after at least three years of venom immunotherapy. A decrease in basophil responsiveness correlates with tolerated sting challenge. Furthermore, the persistent decline in IgE levels and, by monitoring the cytokine profiles, a shift from a Th2 to Th1 immune response, can be observed. In addition, the generation of regulatory T and B cells has proven to be essential for inducing allergen tolerance. Most studies on the mechanisms and effectiveness data have been obtained during venom immunotherapy (VIT). Despite the high success rate of VIT, allergen tolerance may not persist for a prolonged time. There is not much known about immune mechanisms that assure long-term tolerance post-therapy.

Biomarkers of the Severity of Honeybee Sting Reactions and the Severity and Threshold of Systemic Adverse Events During Immunotherapy.

BACKGROUND: A biomarker that could identify individuals at high risk for severe honeybee sting allergic reaction and/or systemic adverse events (SAEs) during venom immunotherapy (VIT) would improve the management of patients with honeybee (HB) venom allergy. OBJECTIVE: To identify biomarkers for risk of severe sting reactions or SAEs during VIT. METHODS: We recruited 332 patients undergoing HB VIT. We ascertained predictors of the severity of the field-sting reaction and the severity and threshold of SAEs during VIT. We assessed the use of cardiovascular medications; baseline serum tryptase (BST) levels; specific IgEs to HB venom, rApi m 1, and rApi m 10; and basophil activation test (BAT) response. RESULTS: Significant and independent predictors of a severe HB field-sting reaction were age (P = .008), an absence of skin symptoms (P = .001), BST (P = .014), and BAT response at an HB venom concentration of 0.1 µg/mL (P = .001). Predictors of severe SAEs during HB VIT were age (P = .025), BST (P = .006), and BAT response (P = .001). BAT response was also an individual and significant predictor of any SAEs and SAEs at a low cumulative allergen dose (median, 55 µg) during VIT build-up (P < .001). The use of ß-blockers and angiotensin-converting-enzyme inhibitors and specific IgE levels were not associated with the severity of HB field-sting reactions or VIT SAEs. CONCLUSIONS: BST and basophil activation are independent risk factors for severe HB sting anaphylaxis and SAEs during HB VIT. BAT response was the best biomarker for any SAEs and a lower threshold of SAEs during HB VIT. These risk factors can help guide recommendations for VIT and overcome systemic reactions to HB VIT.

Routine KIT p.D816V screening identifies clonal mast cell disease in patients with Hymenoptera allergy regularly missed using baseline tryptase levels alone.

BACKGROUND: Clonal mast cell disorders and elevated basal serum tryptase (BST) levels with unknown cause(s) are associated with severe Hymenoptera venom-triggered anaphylaxis (HVA). However, some individuals with clonal disease have a normal BST level (<11.4 ng/mL). OBJECTIVE: Our aim was to evaluate whether screening for KIT p.D816V in the blood is a useful clinical tool to risk-stratify patients with venom allergy. METHODS: We prospectively recruited 374 patients with Hymenoptera allergy and no overt signs of mastocytosis who were referred to our center during the years 2018 and 2019. KIT p.D816V was determined in their peripheral blood by quantitative PCR, and tryptase genotyping was performed by droplet digital PCR. RESULTS: In all, 351 patients (93.9%) had normal levels of BST, and KIT p.D816V was detected in 8% of patients (28 of 351), predominantly in patients with the most severe Mueller grade IV anaphylaxis (18.2% [24 of 132] vs 1.8% in patients with lower grades [4 of 88 with grade III and 0 of 131 with other grades]; P < .001). In grade IV patients with a normal BST level, KIT p.D816V was associated with more severe symptoms, including a significantly higher frequency of loss of consciousness (58.3% [14 of 24] vs 34.3% [37 of 108]; P = .03) and absence of skin symptoms (41.7% [10 of 24] vs 15.7% [17 of 108]; P = .004). Among patients with a normal BST level, KIT p.D816V (OR = 10.25 [95% CI = 3.75-36.14]; P < .0001) was the major risk factor associated with severe HVA. Hereditary α-tryptasemia (HαT) due to increased germline copies of TPSAB1 encoding α-tryptase was the most common cause (65.2% [15 of 23]) of elevated BST level in patients with HVA, and together with KIT p.D816V, it accounted for 90% of BST level elevations (20 of 23) in patients with HVA. CONCLUSION: These results indicate that routine KIT p.D816V screening identifies clonal disease in high-risk patients with HVA who are regularly missed when BST level is used alone.

Immunological Outcomes of Allergen-Specific Immunotherapy in Food Allergy.

IgE-mediated food allergies are caused by adverse immunologic responses to food proteins. Allergic reactions may present locally in different tissues such as skin, gastrointestinal and respiratory tract and may result is systemic life-threatening reactions. During the last decades, the prevalence of food allergies has significantly increased throughout the world, and considerable efforts have been made to develop curative therapies. Food allergen immunotherapy is a promising therapeutic approach for food allergies that is based on the administration of increasing doses of culprit food extracts, or purified, and sometime modified food allergens. Different routes of administration for food allergen immunotherapy including oral, sublingual, epicutaneous and subcutaneous regimens are being evaluated. Although a wealth of data from clinical food allergen immunotherapy trials has been obtained, a lack of consistency in assessed clinical and immunological outcome measures presents a major hurdle for evaluating these new treatments. Coordinated efforts are needed to establish standardized outcome measures to be applied in food allergy immunotherapy studies, allowing for better harmonization of data and setting the standards for the future research. Several immunological parameters have been measured in food allergen immunotherapy, including allergen-specific immunoglobulin levels, basophil activation, cytokines, and other soluble biomarkers, T cell and B cell responses and skin prick tests. In this review we discuss different immunological parameters and assess their applicability as potential outcome measures for food allergen immunotherapy that may be included in such a standardized set of outcome measures.

Clinical and immunological differences between asymptomatic HDM-sensitized and HDM-allergic rhinitis patients.

BACKGROUND: Confirmation of the clinical relevance of sensitisation is important for the diagnosis of allergic rhinitis. OBJECTIVE: To investigate the usefulness of an in vitro basophil activation test and component-resolved diagnosis in distinguishing between symptomatic allergic rhinitis patients and asymptomatic sensitization to house dust mites (HDMs). METHODS: Thirty-six subjects with a positive skin prick test (SPT) for HDM were divided into a symptomatic (n = 17) and an asymptomatic (n = 19) group on the basis of their clinical history and a nasal provocation test. A basophil CD63 response to in vitro stimulation with Dermatophagoides pteronyssinus whole allergen extract and the IgE reactivity profiles for Der p 1, 2, 4, 5, 7, 10, 11, 14, 15, 18, 21, 23 were evaluated. Serum IgE and IgG specific to D pteronyssinus whole allergen extract and total IgE were measured. RESULTS: There were no statistically significant differences in the levels of IgE (IgE levels were higher in symptomatic patients with P = 0.055) and IgG specific to D pteronyssinus and total IgE. Symptomatic patients showed a lower threshold for in vitro basophil activation (3.33 ng/mL vs 33.3 ng/mL), a higher area under the curve (AUC) of basophil activation (171 vs 127) (P = 0.017), a higher response to positive control with anti-FcεRI stimulation (97% vs 79%) (P < 0.001), a recognition of more HDM allergens (4 vs 2) and more frequent sensitization to rDer p 7 (P = 0.016) and rDer p 23 compared to asymptomatic subjects (P = 0.018). There was a positive correlation (r = 0.63; P < 0.001) between the number of recognized allergens and the AUC of basophil activation. CONCLUSION AND CLINICAL RELEVANCE: In the subjects studied, the differences in the basophil response to D pteronyssinus allergen extract, number of recognized HDM allergens and reactivity to rDer p 7 and rDer p 23 distinguish symptomatic from asymptomatic HDM sensitisation better than SPT or allergen extract-specific IgE. Information regarding the clinical relevance of sensitization is important for the prescription of allergen-specific immunotherapy.