Determining the Cause of Discrepant Results in HCV NAT Comparative Tests

Cho, Hyun Jin; Lee, Jae Sook; Kim, Myung Han; Huh, Kwang; Park, Quehn; Cho, Nam Sun

Abstract

BACKGROUND
The Korean Red Cross blood laboratory centers have been performing comparative tests for NAT reactive specimens since February 2005. However, five discrepant specimens were found in HCV-diluted specimens between 2007 and 2008 and the reasons for this has been investigated.
METHODS
For the five discrepant specimens, the HCV RNA concentration was measured in 5 tubes for each speciment. Subsequently, in order to compare the sensitivity of the low titer specimens measured by RT-PCR and TMA, comparative tests of diluted samples were examined six times per sample. Finally, the genotype was tested in order to determine the characteristics of the discrepant samples.
RESULTS
Result of the quantitative tests for HCV RNA demonstrated that aliquots of the plasma bag were homogenous in term of viral load quantitation. As a result of the comparative test, all samples were found to contain over 1.0x10(1) IU/mL as detected by the two analytical systems. In contrast, those less than 1.0x10(1) IU/mL were not entirely detected by the two systems.
CONCLUSION
It was impossible to completely detect using the two NAT system and the detection rates for both systems were equivalent for the samples examined. In particular, with respect to HCV, it may be undetectable on the NAT test because viral load decreases rapidly before and after sero-conversion. This result indicates that anti-HCV and NAT should be performed together as an HCV screening test prior to blood donation.