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Transfusion safety has undergone last two decades significant improvement and many measures have been introduced to achieve near the “zero risk” goal in blood safety. The significant improvement was implementation of nucleic acid testing (NAT) in blood screening worldwide. The main advantages of NAT screening are detection of window period (WP) of infections and identification of occult hepatitis B infections, offering blood centers higher sensitivity in detection of transfusion transmitted infections (TTI). Croatia implemented individual donation NAT testing in March 2013 as a routine blood screening program, concordantly with serological screening. ID-NAT screening was introduced after reorganization of blood transfusion service in whole country and is centralized on one site in CITM. Aims: We found 2 WP infections during three years after NAT implementation. One WP was HIV-1 infection two years ago and second is WP HBV infection presented in this case report. Methods: From 2013-2016 a total of 573.365 donations from voluntary blood donors in Croatia were collected and screened for HBV, HCV and HIV-1 using ID-NAT, by a multiplex transcription-mediated amplification, TMA test on Procleix Tigris System (Grifols, Spain). Donations that were repeatedly reactive were submitted to additional discriminatory assay to resolve which viral genome was present, and then the confirmatory PCR testing was done. All initial reactive donations were submitted to anti-HBc testing. For HBsAg donations were screened by Abbott Prism HBsAg test (Abbott, USA). HBV-DNA viral load was detected by COBAS AmpliPrep/COBAS TaqMan HBV test, V2.0 (Roche Diagnostics, Germany). The donors were recalled for follow-up studies and the collection of clinical and epidemiologic data. Results: By a routine ID-NAT checkup of a 30-years old repeat donor (16 donations) we found positive ID-NAT triplex screening test with negative all serological screening markers (HBsAg (S/CO 0, 66), HIV Ag/Ab, anti-HCV i anti-TP. Once the NAT was repeatedly reactive three times, the discriminatory assay was performed and found to be dHBV positive while all HBV serological markers were negative. Viral DNA was confirmed and determined load as 1.11E+2 IU/mL. In the follow up sample taken 14 days after the index donation, we determined the increasing HBV viral load 1.06E+03 IU/mL, and this time also positive HBsAg with S/CO of 4, 01 and all other HBV markers (anti-HBs, anti-HBc IgG/IgM, HBeAg and anti-HBe) negative. Donor confirmed risk sexual behavior 1 month before donation. Summary/conclusion: ID-NAT offered significant early window period closure and prevented a moderate number of residual HBV transmissions previously not detected by HBsAg assays. HBV still remains the most frequent TTI in many countries, as well in Croatia. The infection risk is mainly related to HBsAg negative units collected in WP or during late stage of infection and highly sensitive ID-NAT could detect both. The case report shows successful prevention of the possible HBV transmission by ID-NAT screening. |
