The cultured lymphocytes (NAMALWA) known to contain EBV genome were collected as internal control. The applicability of the internal control with commercial EBV kits was evaluated, and the amounts in international units by tracing the internal control to the international standard were established. The panel consisted of 5 blindly coded samples diluted with human plasma and distributed to external quality assessment participates in Shanghai. The results from the participates were summarized and analyzed.

The original NAMALWA cells were all positive with different commercial EBV PCR kits. The concentration of internal control valued by international standard was 2.13×10⁵ IU/mL. False positivity and false negativity errors were found in parts of participating laboratories. The coincidence rates were 100% for high-concentration samples (10⁵ and 10⁴ IU/mL), 92% and 40% for low-concentration samples (10³ and 10² IU/mL) and 90% for negative samples, respectively. For samples replicated in the panels, the average coefficient of variation (CV) for intra-laboratory was 4.1% (1.4%-11.3%), and that for inter-laboratory was 6%. Good overall linearity was observed for most of the laboratories (75%).

The quality control materials for EBV PCR kits have been established successfully, and the applicability in external quality assessment is proved. These results indicate that most of participating laboratories show good performance in determining EBV DNA, and it is necessary for individual laboratories to improve their operation.