Background and rationale: Allopurinol is a first-line urate-lowering therapy for gout but is a leading cause of severe cutaneous adverse reactions (SCARs), including SJS/TEN and DRESS. These reactions carry substantial morbidity, mortality, and healthcare costs. Genetic susceptibility-particularly carriage of HLA-B\*58:01-has been consistently associated with allopurinol-induced SCARs, and pre-treatment HLA screening has reduced SCARs in several Asian settings. However, implementation evidence in Vietnam remains limited. This study is designed to generate local clinical and economic evidence to support an HLA-guided prescribing strategy.
Study objectives:
Describe the prevalence of HLA-B\*58:01 among adult Vietnamese patients with gout initiating allopurinol for the first time.
Compare effectiveness and safety outcomes between an HLA-guided strategy (allopurinol for HLA-B58:01 negative; febuxostat for HLA-B58:01 positive) and a non-tested febuxostat strategy.
Evaluate the cost-effectiveness of HLA-B\*58:01 screening in preventing SCARs and informing treatment selection.
Study setting and timeframe: Single-center study at Hai Phong International General Hospital, Vietnam, from January 2025 to June 2027.
Design overview:
Descriptive cross-sectional component to estimate HLA-B\*58:01 positivity among tested, eligible patients.
Prospective comparative follow-up over 12 months to evaluate real-world effectiveness and safety of urate-lowering strategies.
Cost-effectiveness analysis using direct medical costs.
Participants:
Inclusion criteria include age ≥18 years, gout diagnosis according to ACR/EULAR 2020, first-time indication for allopurinol, and willingness to provide clinical data and undergo HLA testing (for tested groups). Exclusion criteria include prior allopurinol exposure or prior allopurinol hypersensitivity, severe comorbid/complex conditions likely to confound treatment (e.g., end-stage kidney disease, advanced malignancy, bone marrow transplantation, current immunosuppression), or inability to adhere to follow-up.
Interventions/Groups:
Group 1 (HLA-B\*58:01 negative; allopurinol): participants tested negative and start allopurinol.
Group 2 (HLA-B\*58:01 positive; febuxostat): participants tested positive and use febuxostat as an alternative.
Group 3 (No HLA test; febuxostat): participants treated directly with febuxostat without HLA testing.
Procedures and follow-up schedule:
HLA-B\*58:01 genotyping is performed on whole blood using PCR with sequence-specific primers; results are classified as positive or negative.
Follow-up visits at baseline, 1, 3, 6, and 12 months.
Clinical and laboratory monitoring includes serum uric acid and safety labs (AST/ALT, creatinine/eGFR) at predefined time points; gout flare frequency and severity are recorded (including pain assessment using VAS).
SCARs are actively surveilled and clinically diagnosed; supportive laboratory findings include eosinophilia and hepatic/renal involvement when applicable.
Outcome measures:
Genetic outcome: prevalence of HLA-B\*58:01 positivity among tested participants.
Effectiveness outcomes: change in serum uric acid over time; proportion achieving target uric acid control; frequency and severity of gout flares during follow-up.
Safety outcomes: incidence of SCARs (SJS, TEN, DRESS); other adverse events including liver enzyme elevation and renal function deterioration; mild hypersensitivity manifestations (e.g., pruritus, urticaria).
Economic outcomes: direct costs of HLA testing, drug therapy, laboratory monitoring, and SCAR management (hospitalization, medications, procedures, investigations). Cost-effectiveness metrics include the cost per unit of SCAR risk reduction and comparative total costs between strategies.
Sample size considerations:
A descriptive sample size is calculated to estimate HLA-B\*58:01 prevalence, and a comparative sample size is calculated for effectiveness/safety comparisons between allopurinol and febuxostat strategies; the planned comparative cohort is approximately 114 participants per treatment strategy group.
Ethics:
The study is conducted in accordance with the Declaration of Helsinki and Good Clinical Practice. Participants provide informed consent; confidentiality is maintained; participants may withdraw at any time without affecting standard clinical care.
