Collaborative study to establish a replacement World Health Organization International Standard for parvovirus B19 DNA nucleic acid amplification technology (NAT)-based assays

Background and objectives The aim of the study was to replace the 1st World Health Organization International Standard for parvovirus B19 DNA for nucleic acid amplification technique (NAT)-based assays (code 99/800). Two lyophilized preparations (coded 99/800 and 99/802) had been evaluated in the original collaborative study. The present study re-evaluates these two preparations in terms of potency, stability and encapsidation of virus DNA. Materials and methods The 1st International Standard (99/800) and 99/802 were re-coded as Samples 1 and 2, respectively. The samples were distributed to six laboratories and assayed on four separate occasions. Accelerated thermal degradation samples of the two preparations were examined after storage at 20 degrees C for 7 years. Nuclease treatment was used to investigate the encapsidation of virus DNA. Results Data were returned from a total of six different quantitative NAT-based assays. The results of the present study confirm those of the original, with no significant differences found in estimated international units (IU)/ml for the 1st International Standard (Sample 1 in this study) and the proposed replacement preparation, Sample 2 (99/802). Accelerated thermal degradation studies demonstrate that both samples are very stable, with no loss of potency after storage at 20 degrees C for 7 years. Both lyophilized preparations contained the majority of B19V DNA encapsidated in virions. Conclusions On the basis of the data presented in this collaborative study, Sample 2 (code number 99/802) was established as the 2nd International Standard for parvovirus B19 DNA for NAT-based assays with a potency of 106 IU/ml (500 000 IU/vial).