Quality Control Points and POCT Management of Respiratory Syncytial Virus Antigen Detection Kit (Colloidal Gold Method)

Quality Management Challenges of Colloidal Gold Method in POCT Settings

Respiratory syncytial virus (RSV) antigen detection kits (colloidal gold method) are widely used in point-of-care testing (POCT) scenarios such as fever clinics, pediatric emergency departments, and community hospitals due to their ease of operation and rapid results. However, the implementation of POCT also brings a series of quality control issues: non-professional laboratory personnel performing operations, environmental temperature and humidity variations, and non-standard sample processing can all affect result accuracy. Therefore, establishing standardized operating procedures and quality control systems is particularly critical.

Kit Storage and Shelf-Life Management

Colloidal gold method kits are generally required to be stored in a dry, light-protected place, typically at a temperature range of 2-30°C. During high-temperature summer or low-temperature winter conditions, direct exposure of reagents to extreme conditions should be avoided. Each batch of kits should have a clear lot number and expiration date, and package integrity must be verified before use. Reagents after opening (e.g., damaged desiccant bags) may experience reduced sensitivity and should be discarded promptly. Laboratories or clinical departments should establish reagent requisition registration and inventory tracking systems to prevent the use of expired products.

Standardization of Sample Collection and Processing

The quality of nasal swab or nasopharyngeal swab collection directly determines the success or failure of antigen detection. Operators should receive standardized training: the swab should be inserted at least 2-3 cm into the nasal cavity, rotated 3-5 times, and left in place for 10 seconds to adsorb more cells. After collection, the swab should be promptly placed into the extraction tube, and buffer solution should be added dropwise and thoroughly mixed according to the instructions. The extracted sample should be tested within the specified time (usually within 30 minutes). For infants and young children, smaller swabs may be used, but sampling depth must still be ensured. Common errors include insufficient swab collection depth, inadequate sample volume, or hemolyzed samples, all of which can lead to false negatives.

Quality Control of Result Interpretation

Result interpretation for the colloidal gold method should be performed within the specified time after sample application (e.g., 15-20 minutes); interpretation too early or too late may produce erroneous results. The color intensity of the test line is positively correlated with viral load, but weak positive bands are easily overlooked. It is recommended that positive and negative controls be included with each batch of tests to verify reagent validity. For internal quality control, weak positive reference materials can be used to assess inter-batch variation. Temperature and humidity should be recorded for each test; if environmental conditions deviate from the range permitted by the reagent instructions, result reliability is reduced.

Improvement of POCT Management Systems

Departments using respiratory syncytial virus (RSV) antigen detection kits (colloidal gold method) should develop written SOPs specifying personnel training, operating procedures, quality control frequency, and handling of abnormal results. Quality control evaluation should be conducted at least once per month, including calculation of sensitivity, specificity, positive predictive value, and other indicators (external quality assessment may be utilized). In cases of consecutive false negatives or abnormal positive rates, reagent lot numbers and operating procedures should be traced, and timely communication with the manufacturer should be initiated. Hospital management should assign oversight responsibilities to a POCT coordination group to ensure uniform standards across all use sites.

Regulatory Compliance and Instructions for Use Requirements

In China, this type of kit is classified as a Class II in vitro diagnostic medical device and requires registration with the National Medical Products Administration. Using institutions should verify the product registration certificate number, applicable instrument models (if applicable), and performance specifications. The instructions for use must clearly state the intended use, detection principle, limitations, storage conditions, and other information. Operators must carefully read and follow them, and must not arbitrarily change sample types or reaction times. For emerging variant strains, the detection capability of the kit may be affected, and manufacturers' statements and updates should be monitored.