Delayed diagnosis of Plasmodium vivax malaria and associated factors among Thai patients and patients from neighboring countries at the Hospital for Tropical Diseases, Bangkok, Thailand

PURPOSE: Plasmodium vivax is the predominant malaria species in Southeast Asia, yet diagnosis may be delayed in non-endemic urban settings where clinicians encounter malaria infrequently. This study described patient characteristics and identified factors associated with delayed diagnosis of P. vivax malaria at the Hospital for Tropical Diseases (HTD), Bangkok, Thailand. METHODS: A retrospective study was conducted among patients admitted with P. vivax malaria at HTD between 2010 and 2024. Data collected included demographics, travel history, illness and healthcare-seeking history prior to admission, clinical manifestations, laboratory findings, and outcomes. Characteristics of patients with and without delayed diagnosis were compared. Logistic regression was used to identify factors independently associated with delayed diagnosis. RESULTS: Among 384 patients, 58.3% experienced delayed diagnosis (> 4 days from symptom onset). Care-seeking delay (> 3 days) occurred in 73.7%, medical diagnostic delay (> 1 day) in 14.1%, and misdiagnosis at the first healthcare facility in 25.5%. Independent factors of delayed diagnosis included age 45-54 years (adjusted odds ratio [AOR] 2.79; 95% CI 1.12-6.94; p = 0.027); working as an employee/office worker/business owner (AOR 4.93; 95% CI 1.19-20.50; p = 0.028); no prior history of malaria (AOR 2.36; 95% CI 1.26-4.42; p = 0.008); and misdiagnosis at the first healthcare facility (AOR 2.99; 95% CI 1.52-5.89; p = 0.002). CONCLUSION: Delayed P. vivax malaria diagnosis was common in this urban near-elimination setting, with care-seeking delay contributing more than medical diagnostic delay. Age 45-54 years, office-based occupation, no prior history of malaria, and initial misdiagnosis were independently associated with delayed diagnosis. Malaria should be considered in febrile patients with relevant epidemiological exposure.