AB76 Abstracts J ALLERGY CLIN IMMUNOL FEBRUARY 2022 Gastric Acid .

Abstracts AB77J ALLERGY CLIN IMMUNOLVOLUME 149, NUMBER 2Mono and Biallergenic-Dendrimer Based SilicaParticle for Specific IgE Determination toBetalactamsMaria Vega, PhD1, Violeta Gil-Oca na2, Isabel Jim enez-Sanchez1, Cristobalina Mayorga, PhD3, Inmaculada Do na4, Jose Cespedes5, Yolanda MD PhDVida2, Ezequiel P erez-Inestrosa2, Maria Torres JaAÓn,FAAAAI6; 1BIONAND, IBIMA, 2University of Malaga, 3IBIMA,4IBIMA, Hospital Regional Universitario de M alaga, 5IBIMA, BIONAND, 6Hospital Regional Universitario de Malag.RATIONALE: Available immunoassays for diagnosing betalactam (BL)allergy have limited sensitivity and poor specificity. They are based ondifferent cellulose polymers with betalactam-poly-L-lysine conjugatescovalently attached, to which specific IgE (sIgE) binding occurs. Herein,we propose the use of nanomaterials consisting on silica particles highlyfunctionalized with drug-dendrimer conjugates (including mono- and biallergenic structures), as precise and controlled solid phases able toimprove the tests’ reliability.METHODS: Silica particles of 500 nm diameter were functionalized withdendrimers, followed by the coupling with amoxicillin and/or benzylpenicillin allergenic determinants. Immunoassays were performed using boththese silica particles and conventional cellulose discs, as solid phases forsIgE capturing, and a radio-labelled anti-IgE for sIgE detection. Evaluationwas carried out in tolerant subjects to BLs (N510) and patients withconfirmed immediate allergic reaction to amoxicillin (N521), diagnosedby skin test positive to amoxicillin or the presence of amoxicillin-sIgE byImmunoCAP, and classified as selective to amoxicillin (N512) orbenzylpenicillin cross-reactive (N59). ROC curves for each solid phasewere analyzed to select the thresholds.RESULTS: Thresholds were established at different percentages of RASTto obtain the best sensitivity/specificity balance. The area under the ROCcurve (AUC) for all silica particles, with amoxicillin, benzylpenicillin orboth BLs simultaneously (AUC51), denotes an excellent capacity ofdistinguishing allergic patients from tolerant subjects, improving valuesobtained with cellulose discs (AUC50.77-0.92).CONCLUSIONS: The use of nano-scaled silica particles improved theresults of available immunoassays techniques in terms of sensitivity andspecificity, providing the possibility of testing different BLs, potentiallysimultaneously.232Educational Intervention to Improve Skin TestUtilization in Low-Risk Penicillin AllergyJohn Kuster1, Jason Kwah, MD2; 1Yale University, 2Yale UniversitySchool of Medicine.RATIONALE: Patients with low-risk penicillin allergy histories canproceed to direct challenges without preceding skin testing, howeverpractice patterns vary. We aimed to evaluate physician attitudes todirect challenges in low-risk patients and examine the effect of aneducational intervention utilizing a validated clinical decision-makingtool (PEN-FAST).METHODS: We surveyed physicians in our adult allergy practice on ascale of 1-10 in areas of comfort (15very uncomfortable, 105verycomfortable), evidence for direct challenges (15very weak, 105verystrong), and past experience with low-risk patients having positive skintesting (15almost never, 105almost always). Educational interventionusing the PEN-FAST tool was then provided. Retrospective chart reviewwas performed comparing skin testing rates 6 months prior to and after theintervention.RESULTS: Physicians surveyed had varying comfort for direct oralchallenges in low-risk patients (mean55.8, range59.0), despite notingstrong evidence supporting its use (mean58.2, range54.0) and lessexperience with low-risk patients having positive penicillin skin testresults (mean52.33, range55.0). During the study period 44 patients hadpenicillin allergy testing. In the 6-month pre-intervention period 16/22patients had low risk histories (PEN-FAST score 3) and all 16 were skintested prior to considering oral challenge. In the 6-month post-interventionperiod 15/22 patients tested had low risk histories, with 11 skin tested priorto oral challenge. This 27% decrease in post-intervention skin testing ratewas significant (p50.04). All direct challenges were well tolerated.CONCLUSIONS: An educational intervention reduced unnecessary skintesting in low-risk patients. Given wide variation in physician comfort,standardization utilizing PEN-FAST may encourage direct challenges inappropriate patients.233THE ROLE OF CLAVULANIC ACID IN IMMEDIATEALERGIC REACTIONS TO BETA-LACTAMSNatalia Blanca-L opez1, Ana Maria Prieto-Moreno Pfeifer1, Isabel TorresRojas, CME1, Diana P erez-Alzate1, M Luisa Somoza1, Elisa HarounDiaz1, Maria Vazquez de La Torre1, Paula Lopez, MD1, Maria D. CerveraGarcia1, Carlos Alberto Blanco Mota1, Francisco Javier Ruano1, MiguelBlanca, MD PhD1; 1Infanta Leonor University Hospital.RATIONALE: Among betalactams-antibiotics(BLs), the combinationamoxicillin-clavulanic(AX-CLAV) is being increasingly prescribed inpatients of all ages, involved in up to 80% of BL allergy reactions. Our aimwas to evaluate the role of Clavulanic acid (CLAV) in this type of drugallergy, with special attention on selective immediate-reactions(IRs).16 years, evaluatedMETHODS: A prospective study including patients in our allergy service (Hospital Infanta Leonor,Madrid, Spain) from 2011to 2020, after reporting an immediate reaction to AX-CLAV. For thediagnosis we followed the EAACI-general-guidelines proposed by theEuropean Network on Drug Allergy(ENDA), with some modifications. Wefirst performed skin-testing followed, if negative, by drug-provocationtest(DPT). According to the results patients were classified into 4 groups:A)allergy to classical BP determinants G), B)selective-allergy to AX, C)selective-allergy to CLAV, D)co-sensitization to CLAV plus penicillingroup determinants or AX.RESULTS: Of a total of 1170 patients evaluated, 104 with IRs wereconfirmed as allergic: 36.5% to classical BP determinants, 26.9% to AX,32.7% to CLAV, and 3.8% to CLAV plus penicillin determinants or AX. Ingroups A, B and C diagnosis was established by skin-testing in 79%, 75%and 47% of the cases, respectively (P 0.001). DPT was necessary todiagnose the remaining cases. Concerning clinical symptoms, anaphylaxispredominated over urticaria/angioedema in all groups.CONCLUSIONS: More than 30% of cases with confirmed IRs after AXCLAV intake are confirmed as selective reactors to CLAV, beinganaphylaxis the most frequent clinical entity presented. The sensitivityof Skin-testing as diagnosis-tool for this group was bellow 50%.SUNDAY231

AB78 Abstracts234Comparison of two strategies for increasingprimary care referral for penicillin allergytestingSUNDAYRohan Achar1, Danielle Devlin, MD1, Josiah Smiley, MD1, HallieOBranovic, MSN RN NP-C1, Rajan Ravikumar, MD1, AlanBaptist, MD MPH FAAAAI1, Eric Walford, MD1; 1University ofMichigan.RATIONALE: Approximately 90% of documented penicillin allergiesare inaccurately reported, resulting in overuse of broad-spectrum antibiotics. The goal of this study was to determine if proactive phone calls vs. inperson clinic conversations with a PCP would result in a differentialnumber of patients who were referred and evaluated for their penicillinallergy.METHODS: Adult patients with a documented penicillin allergy at ageneral medicine clinic were identified through the medical record.Patients were randomized to either receive a phone call, or have a reminderplaced in their PCP’s appointment schedule, to discuss penicillin allergytesting. Eligible and interested patients underwent skin testing and oralchallenge at an outpatient allergy clinic. Referrals, scheduling, attendance,and testing outcomes were tracked over one year. Pearson’s Chi-squaredtest was used for analyses.RESULTS: One hundred twenty-two patients were identified and randomized to the call (N565) or in-person (N557) group. More patientswere referred to allergy testing from the call group than the in-person group(65% vs. 32%, p 0.01). However, patients in the in-person group weremore likely to attend testing after referral (50% vs. 19%, p50.034).Resultantly, there was no difference in the overall rate of testing (call 12%vs. in-person 16%, p50.770). Of the patients tested, 88% tested negativeand had their penicillin allergy removed.CONCLUSIONS: Calling patients with documented penicillin allergiesis more likely to generate a referral than relying on PCP discussion duringclinic visits. However, patients are more likely to actually attend a testingappointment if their PCP discusses testing during a clinic visit.235Current Knowledge and Management ofPenicillin Allergy by Primary Care Physiciansand Points for ImprovementYoram Faitelson1; 1Faculty of Medicine, Tel Aviv University, Tel Aviv,Israel.RATIONALE: Penicillin allergy is commonly misdiagnosed, leading to anegative impact on patients’ health. This study aimed to evaluate theknowledge and management of penicillin allergy by primary carephysicians (PCP), to investigate if PCP are willing to perform penicillinallergy evaluation (PAE) and what will facilitate such an evaluation.METHODS: A cross-sectional study using a 16-question questionnairethat was emailed to family physicians and pediatricians. The questions,utilizing case-scenario, focused on knowledge and management ofpenicillin allergy and on the motivation of PCP to perform PAE.RESULTS: Out of 328 PCP, 169 pediatricians (55%) and 134 familyphysicians (45%) completed the questionnaire. Only 64% of familyphysicians, compared to 88% of pediatricians, believed that PAE isimportant. Seventy percent of PCP overestimate the duration of penicillinallergy and 30% overestimate its severity. While 90% of PCP correctlyrecognized anaphylactic reaction to penicillin, 60% failed to recognizesevere delayed reactions (Such as Steven’s Johnson Syndrome). Bothgroups stated that having the appropriate equipment and staff are the mostimportant factors needed to perform PAE in the community. Givingappropriate resources, 62% of pediatricians and 42% of family physicianswill perform PAE. Junior pediatricians (less than 10 years seniority) weremore likely to perform PAE, compared to senior pediatricians (93% vs.52%, P50.03, respectively).CONCLUSIONS: Additional education is required to PCP regarding thenatural history of penicillin allergy and the management of severe delayedJ ALLERGY CLIN IMMUNOLFEBRUARY 2022reactions. By providing appropriate resources, especially to juniorpediatricians, a significant number of PCP are expected to perform PAE.236Raising Awareness among Medical Residents toDe-label Penicillin AllergyVinh Nguyen1, Renee Crawford, DO1, Christine Rukasin, MD1, CindyBauer, MD FAAAAI1, Kristen Samaddar, MD1; 1Phoenix Children’sHospital.RATIONALE: Approximately 90% of US patients with a reportedpenicillin-class antibiotic allergy are able to tolerate penicillin upontesting. The prevalence of these false labels have led to the use ofalternative antibiotics that are more expensive, less effective, and lead tohigher antibiotic resistance. We hypothesized that raising awareness of thisissue to pediatric residents and patients would lead to higher referral ratesto Allergy/Immunology and ultimately de-labeling.METHODS: A retrospective chart review of patients seen in theoutpatient general pediatrics clinic for the prior 6 months was conductedto gather baseline data. Phoenix Children’s Hospital then provided trainingfor residents in the form of didactics and journal club on penicillin allergy.Patients were also educated on the importance of confirming their drugallergy with an allergist. This was achieved through the use of face-to-facepresentations, videos, and handouts. The number of penicillin allergylabeled patients with an initial allergy referral was subsequently tracked bymonth through the electronic medical record. Patients were age 1 to 18years. Logistic regression was used for analysis.RESULTS: 244 charts had a penicillin allergy label pre-intervention. Ofthose charts, 46 had an allergist referral (19% referral rate). After 6 months,253 charts had a penicillin allergy label post-intervention. Of those charts,75 had an allergist referral (30% referral rate) (p50.04).CONCLUSIONS: Pediatric resident and patient education on penicillinallergy may be a useful tool to aid in referrals to Allergy/Immunology forevaluation and likely de-labeling of the penicillin allergy.

Abstracts AB79J ALLERGY CLIN IMMUNOLVOLUME 149, NUMBER 2CD203c showed greater diagnostic value thanCD63 for evaluating immediate reactions toamoxicillin-clavulanic by basophil activationtestJose Cespedes1, Ruben Fernandez-Santamaria1, Gador BogasHerrera, MD2, Maria Salas2, Inmaculada Dona2, Almudena TesteraMontes, PhD2, Cristobalina Mayorga, PhD2, Rocio Saenz de Santa Ma MD PhDria2, Adriana Ariza Veguillas, PhD1, Maria Torres JaAÓn,FAAAAI3; 1Instituto de Investigaci on Biom edica de M alaga-IBIMA,M alaga, Spain, 2Hospital Regional Universitario de M alaga, M alaga,Spain, 3Universidad de M alaga-UMA, M alaga, Spain.RATIONALE: Basophil activation test (BAT) is widely used in theevaluation of immediate allergic reactions to the combination of amoxicillin (AX) and clavulanic acid (CLV). Although the CD63 activationmarker is usually employed, some authors claim that CD203c is better forthese reactions. The aim of this study was to evaluate the real value ofCD63 and CD203c as activation markers in BAT for diagnosing AX-CLVreactions.METHODS: We prospectively evaluated 212 patients with allergicreactions after AX or AX-CLV administration. BAT was performed in allpatients using both CD63 and CD203c as activation markers. Results wereexpressed as %CD63 or %CD203chigh basophils and as stimulation index(ratio between stimulated and unstimulated basophils).RESULTS: From all evaluated patients, 106 were confirmed as allergic toAX, 42 to CLV, and 74 as non-allergic. In AX-allergic patients, BATshowed a sensitivity of 41% and a specificity of 90% using CD63; of 45.7%and 95% with CD203c; and of 50.5% and 88.8% combining both markers.The best predictive values were observed using CD203c: positive predictive value (PPV) 5 92.3% and negative predictive value (NPV) 5 57.2%.Similar results were obtained in CLV-allergic patients, with a sensitivity of42.8% and a specificity of 79.2% for CD63; of 50% and 100% for CD203c;and of 54.8% and 79.2% for the combination. Best predictive values werealso observed using CD203c (PPV 5 100%; NPV 5 77.9%).CONCLUSIONS: CD203c seems to be the best activation marker in BATto evaluate immediate allergic reactions to AX-CLV, with good PPValthough improvable NPV.238Direct Oral Challenge is a Safe and EffectiveStrategy to Delabel Low-Risk Penicillin Allergyin Immunocompromised Patients Admitted tothe ICUGrace Koo, MD1, Joanna Stollings, PharmD1, ChristopherLindsell, PhD1, Mary Lynn Dear, PhD1, Sunil Kripalani, MD, MSc1,Todd Rice, MD1, Elizabeth Phillips, MD FAAAAI FIDSA1, Cosby Stone,MD MPH1, and the VanderbiltLearning Healthcare System Investigators1.1Vanderbilt University Medical Center.RATIONALE: Increasing evidence supports that adults with low-riskpenicillin allergy labels (PALs) can be delabeled with direct oralamoxicillin challenge. Immunocompromised patients admitted acutelyare at increased risk of infection and likely benefit disproportionately fromdelabeling. We investigated the efficacy, safety, effectiveness, andinfection outcomes of immunodeficient patients with low-risk PALsdelabeled in the intensive care setting.METHODS: PAL patients admitted to the Medical Intensive Care Unit(MICU) at Vanderbilt University Medical Center from March 2019 untilMarch 2021 were defined as immunodeficient by: diabetes mellitus, endorgan disease, transplantation, HIV, inflammatory bowel disease, primaryimmunodeficiency, sickle cell disease, malignancy, autoimmune disorders,and immunosuppressive medications. All low-risk PAL patients wereoffered direct challenge with oral amoxicillin. The proportion of immunodeficient patients tolerating direct oral challenge and subsequenttolerance of a penicillin were documented.RESULTS: 156/240 (65.0%) of low-risk PAL patients were defined asimmunodeficient; the most common conditions identified were: diabetesmellitus (75/240, 31.3%), end-organ disease (55/240, 22.9%), malignancy(41/240, 17.1%), autoimmune disorders (26/240, 10.8%), and immunosuppressive medications (43/240, 17.9%). Of these 156, 131 (84.0%)patients underwent amoxicillin challenge and had their penicillin allergydelabeled. 37/131 (28.2%) patients went on to tolerate at least one courseof a penicillin. Collectively, the 37 patients tolerated 64 subsequent coursesof penicillin including: piperacillin-tazobactam (33/64, 51.6%), amoxicillin-clavulanate (8/64, 12.5%), ampicillin (7/64, 10.9%), ampicillinsulbactam (7/64, 10.9%).CONCLUSIONS: Immunodeficiency is a common co-morbidity inpatients admitted to the ICU. When labeled with a low-risk penicillinallergy, point-of-care direct oral challenge with amoxicillin is anefficacious, safe and effective delabeling mechanism.239Dendritic Nanostructures for Effector CellActivation to Study Allergic Reactions toAmoxicillinAmene Ayane1, Sara Bened e2, Alba Rodr ıguez-Nogales1, Tahia Fern andez3, Juan Paris1, Maria Rodriguez3, Isabel Jim enez3, Gador Bogas MDHerrera, MD4, Cristobalina Mayorga, PhD5, Maria Torres JaAÓn,PhD FAAAAI6, Maria Monta nez1; 1Andalusian Centre for Nanomedicineand Biotechnology-BIONAND, M alaga, Spain, 2Instituto de Investigaci on en Ciencias de la Alimentaci on (CIAL, CSIC-UAM), 3AllergyResearch Group, Instituto de Investigaci on Biom edica de M alaga-IBIMA,M alaga, Spain, 4Hospital Civil de Malaga, 5IBIMA, 6Hospital RegionalUniversitario de Malag.RATIONALE: Amoxicillin (AX) is the penicillin currently regarded asthe main culprit in eliciting allergic reactions. According to haptenhypothesis, AX immunogenicity can only be gained by forming covalentconjugates with proteins. Structural properties of conjugates could benano-engineered to be appropriate for crosslinking of specific IgE (sIgE)bound to high-affinity receptor on basophils or mast cells (MCs).METHODS: Bidendron nanostructures, multi-functionalized with amoxicilloyl, and spaced with polyethylene glycol (PEG) chains of distinctlengths (600 - 12000 Dalton) were synthesized. The ability of AX-sIgE torecognize the nanostructures was evaluated by competitive radioimmunoassay using sera from AX-allergic patients. The formation of immunocomplexes was studied by transmission electron microscopy (TEM).Allergenic activities were assessed using bone marrow-derived MCs,primed with mouse anti-AX IgE, and humanized RBL-2H3 cells, primedwith polyclonal antibodies from sera of AX-allergic patients and tolerantsubjects.RESULTS: All nanostructures were recognized by AX-sIgE. Botheffector cell assays revealed that IgE-mediated degranulation is polymericspacer length dependent, taking place only with longer nanostructures(PEG 6000-12000). Nanostructures forming greater proportion of immunocomplexes, and the largest number of antibodies per complex, asvisualized by TEM, were the most successful in activating cellularresponses.CONCLUSIONS: This study evidences the structural limitations of drugconjugates for IgE receptor crosslinking to occur and establishes structuralrequirements for activation of effector cells. A minimum amoxicilloylgroup spacing of 13 nm (PEG 6000) of nanostructures in-solution isnecessary for cell activation, with 18 nm (PEG 10000) distance beingoptimal for effective crosslinking.SUNDAY237

AB80 Abstracts240Beta-lactam Allergy Assessment and SkinTesting (BLAAST)SUNDAYLakhini Vyas1, Karan Raja, PharmD, BCPS, BCIDP, AAHIVP1, SusanMorrison, MD1, Donald Beggs, MD1, Mark Attalla, PharmD, MBA1, Mitesh Patel, PharmD, BCCCP1, Mona Philips, RPh, MAS1; 1Clara MaassMedical Center.RATIONALE: Beta-lactam antibiotics comprise 8-20% of all selfreported medication allergies. Antibiotic allergy misidentification isdetrimental since broad-spectrum alternatives can lead to suboptimaltreatment and potentiate resistance. The multidisciplinary Beta-lactamAllergy Assessment and Skin Testing (BLAAST) program was implemented to facilitate comprehensive allergy history documentation andincrease use of targeted beta-lactams. The study objective was to assessrates of complete allergy histories and beta-lactam days of therapy (DOTBL) per 1,000 days-present before versus after program implementation.METHODS: The BLAAST team screened and interviewed adult inpatients with documented beta-lactam allergies receiving antimicrobialtherapy daily. Patients were stratified as high, moderate, or low-risk of IgEmediated allergy and referred to an allergist for either penicillin skin test(PST) or drug challenge. The electronic medical record was updated withinterview details, drug challenge and/or PST results. The primary endpointwas complete allergy documentation rates. The secondary endpoint wasinpatient DOT-BL. Allergy de-labeling and outpatient beta-lactam prescribing rates were evaluated.RESULTS: One hundred eighty-four were included in the pre-intervention cohort compared to 208 patients in the post-intervention group.Complete allergy histories increased from 49.1% to 71.2% after programimplementation (RR 1.45 [1.24,1.70]). DOT-BL increased from 126.9 to285.7 per 1,000-days-present. There were 91 patient interviews, 75allergist referrals, 2 drug challenges, and 62 PST during the postintervention period. Sixty patients tested negative, all were de-labeled,and 49 had subsequent antibiotic changes. BLAAST cohort patientsreceiving outpatient antibiotics were more likely to receive beta-lactams.CONCLUSIONS: Multidisciplinary beta-lactam allergy managementimproved rates of complete allergy histories and increased use of targetedbeta-lactams.241Direct provocation in children with nonimmediate reaction to beta-lactamChayaniss Pachasidchai, MD1, Watcharoot Kanchongkittiphon, MDPhD2, Wiparat Manuyakorn, MD, PhD2, Kranjana Chayutimaphan2, Wanlapa Jotikastira2, Potjanee Kiew-ngam2, Adithep Sawatchai2; 1Faculty ofMedicine Ramathibodi Hospital, Mahidol University, 2Ramathibodi Hospital, Mahidol university.RATIONALE: Beta-lactam antibiotics (BLs) are frequent causes of drugallergies. We perform direct oral challenge for children with low-risk BLsallergies.METHODS: Children age 4-18 years who had report BLs allergy wereenrolled. Risks were assessed by evidence-based criteria. Low risk patientsunderwent direct oral challenge by 2 graded dose (10/90%) and continuedfor a total of 5 days.RESULTS: A total of 46 children met the criteria for a direct oral BLschallenge, having the mean age was 8.6 years (range from 4-18 years), 25(54.3%) were females. The mean age at BLs allergy diagnosis was 4 years(range from 0.8 -12.7 years). Of these, 34 patients (74%) were penicillinallergy and 12 patients (26%) were cephalosporin allergy. Symptoms ofallergic reaction included 22 (47.8%) maculopapular rash, 15 (32.6%) nonspecific rash, 9 (19.6%) urticarial rash, and 3 isolate GI symptom. Sixchildren (13%) had previously taken a culprit medication before labeledwith drug allergy. Regarding direct oral challenge, 45 (97.8%) childrentolerated the challenge without any reactions. One child (2%) developed aJ ALLERGY CLIN IMMUNOLFEBRUARY 2022reaction on the second dose with urticarial rash resolved with an oralantihistamine. There was no anaphylaxis occurred.CONCLUSIONS: Children categorized as low-risk by risk-stratificationcriteria can perform safe and effective direct oral challenge test to BLsallergy diagnosis.242Detection Of Serum Specific IgE By FluoroEnzyme Immunoassay For The Diagnosis OfImmediate Allergic Reactions To PenicillinsAdriana Ariza Veguillas, PhD1, Gador Bogas Herrera, MD2, FrancescoGaeta3, Mar ıa Salas2, Rocco Valluzzi4, Marina Labella2, Natalia P erezS anchez2, Cristiano Caruso3, Ana Molina Bueno5, Tahia Fern andez6,Cristobalina Mayorga, PhD7, Mar ıa Jos e Torres8, Antonino Romano9; 1Instituto de Investigaci on Biom edica de M alaga-IBIMA, 2Instituto de Investigaci on Biom edica de M alaga-IBIMA, M alaga,

A)allergy to classical BP determinants G), B)selective-allergy to AX, C) selective-allergy to CLAV, D)co-sensitization to CLAV plus penicillin group determinants or AX. RESULTS: Of a total of 1170 patients evaluated, 104 with IRs were confirmed as allergic: 36.5% to classical BP determinants, 26.9% to AX,