Comparison the effect of individual donation NAT and minipool of 16 donations NAT

Objective To investigate the effect of individual donation-nucleic acid amplification test (ID-NAT) and minipool of 16 donations-NAT (P16-NAT) on the results of NAT of blood donors. Methods From February 2009 to June 2009, samples randomly collected from voluntary blood donors in Beijing were tested individually or in pooling of 16 donations by the PROCLEIX ULTRIO assay. For ID-NAT reactive samples with HBsAg, anti-HCV, or anti-HIV serologically unqualified，ID-NAT repeat reactive samples with serologically qualified, and P16-NAT reactive and followed resolution ID-NAT reactive samples, were performed for further discriminatory assays for HIV-1, samples and followed resolution ID-NAT reactive samples，were performed for further discriminatory assays for HBV，HCV and HIV-1 discriminatory reagents.Samples which were HBV NAT+ alone with serologically qualified were further quantified and confirmed of HBV DNA by Roche HBV quantitative PCR, analyzed by HBV serology and were diluted to simulate if they could be detected in P16-NAT. Results （1）Among 7613 samples tested by ID-NAT, 26 were NAT positive, i.e.the ID-NAT positive rate was 0.34% (26/7613). （2）Among 1004 P16 samples from 16 064 blood donations, 27 were NAT positive, i.e. the P16-NAT positive rate was 0.17%（27/16 064）. （3）In serological qualified donations, ID-NAT yield rate (1 in 826, 9/7438) was much higher than P16-NAT (1 in 7875，2/15 750) (χ2=11.880，P＜0.05). All these 9 ID-NAT positive and 2 P16-NAT positive donations were discriminated as HBV NAT positive. There were no HCV NAT yield or HIV NAT yield samples. （4）Dilution assay showed only 2 of the 9(22.22%) ID-NAT HBV yields were detected by P16-NAT. （5）Eight ID-NAT and 2 P16-NAT positive samples were quantified for HBV DNA and confirmed as HBV NAT yield, although the virus loads were very low:2 samples had HBV viral loads of 15 IU/ml and 472 IU/ml, 6 samples <12 IU/ml, and 2 could not be detected in the original samples while had ＜12 IU/ml and 14.3 IU/ml in the 10 times concentrated samples. （6）Among 11 HBV NAT yield cases, 3(27.3%) were possible HBV window-period donors with all HBV seromarkers negative, the other 8 (72.7%) had occult HBV infections with anti-HBc or anti-HBe positive, however anti-HBc IgM negative. （7）The rate of initial P16-NAT reactive pools needed to be further tested by ID-NAT was 2.49%（25/1004）. Initial P16-NAT reactive pools which caused by serologically qualified donations was 0.20%（2/1004）. Conclusions HBV NAT yield cases are detected at a higher frequency with ID-NAT than P16-NAT. In order to avoid samples with low viral loads would be undetected, NAT assay with high sensitivity should be selected and tested in minimized minipool donations or even with individual donation.（Chin J Lab Med，2012，35：53-58） Key words: Blood donors; Nudeic acids; Hepatitis B Virus; Hepacivirus; HIV; Immunoenzyme techniques