Aconitine and related alkaloids are potent cardiotoxins and neurotoxins found in the Aconitum species used in traditional Chinese medicine (TCM), such as 'Chuanwu', 'Caowu' and 'Fuzi'. They pose significant health risks when used inappropriately without professional supervision. Patients with acute aconite poisoning often present with a combination of cardiovascular, neurological, and gastrointestinal toxicities, which can occur after an overdose, inadequate processing of the aconite roots, erroneous use of tincture preparations, and contamination or substitution of other herbs with aconite roots. Timely diagnosis of aconite poisoning remains challenging due to the long laboratory turnaround time. The aim of this study is to develop an aptamer-based lateral flow device (LFD) for point-of-care detection of aconitine and its metabolites (benzoylaconine and aconine) and evaluate its diagnostic performance.

In this study, the investigators will first develop an aptamer-based LFD for point-of-care detection of aconitine, benzoylaconine and aconine in human urine samples. The investigators will perform in vitro selection of binding aptamers for each of the target alkaloids (aconitine, benzoylaconine and aconine) using systematic evolution of ligands by exponential enrichment (SELEX). High throughput sequencing (HTS) and bioinformatics analysis will be performed to characterise the selected aptamers. The selected aptamers will be integrated into ELISA and LFD competition assay. Spiked samples (80 samples, including 20 for each target alkaloids and 20 controls) will be used for calibrating the LFD reader and determining the cutoff points.

The investigators will then conduct a cross-sectional study on stored human urine samples to evaluate the diagnostic performance of the newly developed LFD. The gold standard will be the independent laboratory analysis by the Centre for PanorOmic Sciences (CPOS) at The University of Hong Kong.

Patient urine samples will be stored at 4°C in emergency departments or Chinese medicine clinics. The samples will then be transported to the Laboratory Block of the School of Biomedical Sciences by our research staff within 12 hours of collection. LFD assays will be performed in batch with 5 replicates. 150 µL aliquots of patients' urine sample will be thawed on ice and added to the LFD sample pad. After the flow has completed (approximately 5 minutes), a LFD reader will be used to scan the line intensities for statistical analysis and diagnosis. The operators of the LFD assays will be blinded to the CPOS analytic results.

The primary outcome is the accuracy of the newly developed LFD in detecting aconitine, benzoylaconine and aconine in human urine samples. The secondary outcomes include other diagnostic metrics, such as sensitivity, specificity, positive and negative predictive values, positive and negative likelihood ratios, the area under the receiver operating characteristic curve and their respective 95% confidence intervals (CIs). The hypothsis is that the LFD can achieve a high diagnostic accuracy, with a sum of the lower bounds of sensitivity and specificity 95% CIs exceeding 1.75.

The study will be conducted in full compliance with the Declaration of Helsinki. The risks of participating in this study will be minimal since the recruited participants only need to submit urine samples. This study will also adhere to the safety guidelines of the University of Hong Kong Biological Safety Policy.

Inclusion Criteria (Aconite Poisoned Group):

• adult patients aged 18 years or above
• clinical presentations consistent with acute aconite poisoning, including neurological, gastrointestinal, or cardiovascular symptoms
• exposure to aconite alkaloids within 3 days

Exclusion Criteria (Aconite Poisoned Group):

• refusal of informed consent for urine collection
• alternative explanations for clinical presentations

Inclusion Criteria (Aconite Therapeutic Use Group):

• adult patients aged 18 years or above
• documented history of using aconite for therapeutic purposes, as prescribed by a qualified practitioner in a Chinese medicine clinic
• exposure to aconite alkaloids within 3 days

Exclusion Criteria (Aconite Therapeutic Use Group):

- Refusal of informed consent for urine collection.

Inclusion Criteria (Control Group):

• adults aged 18 years or above
• no documented history of exposure to aconitine, benzoylaconine, or aconine within 30 days
• no clinical evidence of aconite toxicities

Exclusion Criteria (Control Group):

• refusal of informed consent for urine collection
• recent history of poisoning or overdose from any other substances within 30 days

The patient participants are recruited from 3 sources. The Aconite Poisoned Group will include adult patients who present to the emergency departments of Queen Mary Hospital or United Christian Hospital and are reported to the Hong Kong Poison Control Centre for acute aconite poisoning.

The Aconite Therapeutic Group will include adult patients who have therapeutic use of aconite in Chinese Medicine Clinics.

The Control Group will include adult emergency department patients who have no exposure to aconitine, benzoylaconine, or aconine within 30 days and no clinical evidence of aconite toxicities

Additional IRB approval for IPD is required due to local regulations on data privacy