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Background: Basophil activation tests (BATs) are useful in identifying culprits of perioperative anaphylaxis (PA), but their utility remains limited due to technical limitations, cost, and availability. Being able to prioritize patients with likely higher yields for BAT would be useful in reducing costs and manpower. Objective: We sought to investigate whether tryptase levels and clinical parameters may be useful for selecting patients for BATs. Methods: We performed a 10-year retrospective study in Hong Kong to investigate the performance of BATs associated with tryptase levels (taking during PA) and other clinical parameters. Results: Of 90 patients, 70 (77.8%) showed significant tryptase level elevation and 37 (41.1%) had a positive BAT result. BAT-positive patients presented with significantly higher absolute levels (15.9 μg/L vs 9.1 μg/L; P = .018), absolute elevation (12.8 μg/L vs 7.1 μg/L; P = .012), and fold elevation (5.6- vs 4.1-fold; P = .014) of acute tryptase than did BAT-negative patients. Among patients with positive BAT result, 94.6% (35 of 37) demonstrated elevated acute tryptase, significantly more than the BAT-negative group (66.0%; P < .001). In regression analysis, tryptase elevation was the sole significant factor correlated to BAT positivity (odds ratio, 10.14; 95% CI, 2.15-47.85; P = .003). Overall, elevated acute tryptase demonstrated a sensitivity of 94.7% and a negative predictive value of 90.0% in predicting positive results with BATs. Conclusions: We observed that tryptase elevation is a very sensitive predictor of BAT positivity among patients with identified culprits of PA. Acute elevation of tryptase would not only aid in confirming anaphylaxis but may also help guide the decision toward selecting labor-intensive and costly in vitro tests such as BATs.

Background: Chronic spontaneous urticaria (CSU) is an immunologic condition with an estimated prevalence of 0.1%. For CSU that is poorly controlled despite the use of antihistamines, omalizumab is the only treatment approved and recommended by international guidelines. Objective: Our aim was to outline the impact of treatment accessibility on CSU outcomes in the real world. Methods: Serial data on adult patients with CSU receiving care for at least 6 months at a dedicated, immunologist-led urticaria clinic at Grantham Hospital in Hong Kong between 2018 and 2023 were analyzed. Patients’ clinicodemographic data, drug eligibility status (eligible for reimbursement or not), treatment step, and disease activity (weekly Urticaria Activity Score [UAS7]) were collected and compared according to drug eligibility status. Results: This study included 238 patients, 80 (33.6%) of whom were eligible for reimbursement and 158 of whom were not. No significant clinicodemographic differences, including disease activity, were found at baseline. At latest follow-up, significantly more patients in the eligible group were receiving omalizumab (28.7% vs 5.7% [P < .001]), which is equivalent to a multivariate odds ratio of 9.35 (95% CI = 3.689-23.703 [P < .001]). The discrepancy persisted even in patients with moderate-to-severe CSU whose UAS7 was 16 or higher (40.6% [13 of 32] vs 10.2% [6 of 59]; P < .001). In addition, there was significantly less dose reduction (

Background: Hereditary angioedema (HAE) is a rare genetic disease. Patients with type II HAE have normal or elevated C1-inhibitor (C1-INH) levels but C1-INH protein is dysfunctional. C1-INH function requires careful sample handling and technical expertise and may account for the lack of diagnosed patients with type II HAE in resource-limited countries. Objective: We sought to assess the diagnostic performance of elevated C1-INH levels in diagnosing type II HAE. Methods: All patients with confirmed type II HAE in Hong Kong and India were analyzed. Diagnosis was confirmed by persistent low C1-INH function and/or pathogenic SERPING1 gene mutations. Their C1-INH levels were compared with those of matched controls. Results: A total of 31 (14 Chinese, 17 Indian) patients with type II HAE and 31 matched controls were analyzed. Overall, 77.4% (24/31) of patients with type II HAE had elevated C1-INH levels compared with 38.7% (12 of 31) of controls (odds ratio, 2.00; 95% CI, 1.34-2.98; P = .017). C1-INH levels in patients with type II HAE were significantly higher than in controls (52.2 ± 20.0 mg/dL vs 29.1 ±3.6 mg/dL; P < .001). Findings were consistent when C1-INH values in the Chinese and Indian subgroups were analyzed separately. Receiver-operating characteristic curve demonstrated excellent performance for elevated C1-INH levels to diagnose patients with type II HAE with an area under the curve of 0.953 (95% CI, 0.941-0.992; P < .001). Positive and negative predictive values of both a low C4 and an elevated C1-INH level for patients with type II HAE were 100% and 82.9%, respectively. Conclusions: Low C4 and elevated C1-INH levels may be considered as a screening tool for type II HAE, especially in countries where C1-INH function testing is not readily available.

Background: With no approved long-term prophylaxis (LTP) for the prevention of hereditary angioedema (HAE) attacks in Hong Kong, patients rely on compassionate use programs and drug trials. Moreover, studies regarding the use and efficacy of LTP in Asia are lacking. Objectives: Our aim was to assess 2 LTP medications for HAE in Hong Kong: lanadelumab and garadacimab. Methods: A prospective study was performed. Adult patients with a diagnosis of type I or type II HAE with 1 or more expert-confirmed attacks per month were consecutively recruited. The patients had been receiving treatment for at least 6 months. Clinical data were obtained, and questionnaires were administered before treatment periodically for at least 6 months following initiation of LTP. Results: Almost one-third of the patients with HAE experienced frequent attacks and began receiving LTP (8 of the 11 received garadacimab and 3 of the 11 received lanadelumab). At baseline, the time-normalized number of HAE attacks was 2.5 plus or minus 1.3 per month. At month 6, there was an overall reduction of time-normalized number of attacks per month of –2.4 attacks per month (95% CI = –3.3 to –1.5. [P < .01]). The time-normalized number of HAE attacks at month 6 was 0.1 plus or minus 0.1 per month. More than 70% of the patients (8 of 11) were completely attack-free during the 6-month period while receiving LTP, and no patients required hospitalization. LTP improved patients' scores of the Angioedema Quality-of-Life Questionnaire (P < .001) and reduced activity impairment due to health (P = .008). Patients experienced significant improvement across all dimensions of the Treatment Satisfaction for Medication Questionnaire (54.5%-76.8% [P = .002]), and no adverse events were reported. Conclusion: The patients receiving LTP with garadacimab and lanadelumab experienced a significant reduction in number of HAE attacks and improvement in quality of life, and they were satisfied with treatment.

Background: Anaphylaxis is a life-threatening allergic reaction that poses a considerable burden on populations across all ethnicities and age groups. The Hong Kong Multidisciplinary Anaphylaxis Management Initiative (HK-MAMI) was established to streamline the assessment of patients with anaphylaxis via a multidisciplinary and protocol-driven approach. Objective: This prospective study aims to define the etiology, clinical manifestations, and treatment of patients with anaphylaxis in Hong Kong. Methods: Prospective clinical data from allergologic investigations from patients who completed evaluation by the HK-MAMI pathway between January 2017 and August 2022 were analyzed. Results: Of the 161 patients referred via the HK-MAMI, 131 (81.4%) met the diagnostic criteria for anaphylaxis. The median delay in diagnosis was 2 years (range 0-30 years). The majority of anaphylaxis cases were attributed to food-dependent exercise-induced anaphylaxis (FDEIA), especially wheat-dependent exercise-induced anaphylaxis. In acute management settings, paired tryptase samples were taken in only around one-third of anaphylaxis cases, with 82.5% of the samples demonstrating significant elevation. There was a general underprescription of adrenaline autoinjectors, especially for food-related anaphylaxis. Patients with FDEIA had later ages of onset and diagnosis, and they presented with more cardiovascular manifestations. Skin prick tests and specific IgE level tests were able to diagnose 95% of FDEIA cases. Conclusion: Our study highlights the significant burden of FDEIA, and especially WDEIA, in Hong Kong, its association with severe presentations, and difficulties encountered in emergency or primary care settings. We advocate appropriate adrenaline use during acute-care management and discharge plans, as well as taking serum mast cell tryptase samples during acute episodes. Interdisciplinary collaboration remains crucial to upholding proper and optimized care for patients with anaphylaxis in Hong Kong.