Technical Advantages and Quality Control Considerations of Latex Immunochromatography in Multiplex Respiratory Virus Antigen Detection

Technical Principle of Latex Immunochromatography

Latex immunochromatography involves coating specific antibodies onto the surface of latex microspheres, which are then labeled and immobilized on the conjugate pad. When a sample flows through the conjugate pad, the target antigen binds to the antibody-latex complex, forming an immune complex that continues to migrate to the test line, where it is captured by immobilized antibodies and produces a visible color. Latex particles have uniform particle size and a large specific surface area, providing enhanced signal amplification. Compared with the traditional colloidal gold method, latex immunochromatography generally offers higher detection sensitivity and less inter-batch variation.

Comparison with Colloidal Gold and PCR Methods

In multiplex respiratory virus antigen detection, the colloidal gold method has lower cost but limited sensitivity, and may produce false negatives, especially for low-titer samples. The PCR method has extremely high sensitivity but requires specialized equipment, longer turnaround time, and higher cost, making it unsuitable for point-of-care rapid testing. Latex immunochromatography falls between the two: its limit of detection typically reaches 10³–10⁴ PFU/mL, results are available within 15 minutes, and the procedure is simple, requiring no heating or washing steps. For common pathogens such as adenovirus, respiratory syncytial virus, and parainfluenza virus, the latex method offers clear practical advantages in primary care hospitals, emergency departments, and pediatric clinics.

Key Elements of Kit Design

A triplex detection kit must address the issue of cross-reactivity. The specificity of each virus antibody must be validated to avoid nonspecific binding with common pathogens such as rhinovirus and influenza virus. The conjugation process of latex particles, the pore size and hydrophilicity of the membrane material, and the buffer formulation all affect the chromatography speed and signal intensity. A properly designed control line (e.g., anti-human IgG) can monitor reagent efficacy. In addition, the sample treatment solution must balance stable release of viral antigens and suppression of interfering substances.

Quality Control and Common Issues in Use

Routine internal quality control should be performed in laboratory and clinical use, including the use of positive and negative controls. If the control line does not develop color, it indicates reagent failure or operational error, and results should not be reported. Common issues include: slow chromatography due to viscous samples, excessively high background signal (possibly due to sample hemolysis or inappropriate buffer), and difficulty in interpreting weak positive bands. It is recommended that operators receive standardized training, strictly follow the reading time window specified in the instructions, and avoid delayed reading that may cause false positives. For samples with questionable results, confirmation by another method (such as PCR) is recommended. A stable supply chain and proper storage conditions (2–30°C, protected from light and moisture) are also important factors in ensuring kit quality.