以核酸擴增技術評估台灣地區捐血者B型肝炎病毒陽性率

Abstract

在已開發或開發中國家，對捐血者篩檢B型肝炎之策略不同，B型肝炎盛行率低的國家（例如：美國），捐血者篩檢B型肝炎表面抗原（Hepatitis B surface antigen, HBsAg）及B型肝炎核心抗體（Hepatitis B core antibody, anti-HBc）；B型肝炎盛行率高的國家（例如：台灣）， HBsAg陽性率高達15-20%，而台灣地區90%以上的人過去曾經感染或正感染B型肝炎病毒，因而anti-HBc陽性率高，所以在台灣，捐血者目前僅篩檢是否有持續感染的跡象（HBsAg陽性和ALT直升高），而不檢測過去是否發生B型肝炎病毒感染情形（anti-HBc陽性）。然而核酸擴增技術（Nucleic acid testing, NAT）等新技術之發展，各國陸續以NAT篩檢病毒，以縮短空窗期，增加輸血安全。特別是過去感染B型肝炎之人口中約有10-30％血中存在病毒DNA，即使是anti-HBc及anti-HBs皆陽性，傳統上認為過去感染但已恢復之病人，仍有1-10％為HBV DNA陽性，且只是病毒量很低。本研究為了解台灣捐血者以NAT篩檢HBV DNA之效益。研究結果顯示以位於B型肝炎病毒S 基因之引子，進行巢式聚合酶連鎖反應（Nested PCR），其靈敏性（95％ 偵測極限）為10 IU/ml，結果，HBsAg陰性且HBV NAT之陽性率為0.18％，可作為評估捐血者篩檢方式之參考。

Currently, serologic screening is the method used in Taiwan to reduce the frequency of transfusion-transmitted viral infections. The screening program for HBV infection among blood donors differs between developed countries and developing countries. In some developed countries, like the US, blood donors are screened for both hepatitis B surface antigens (HBsAg) and also antibodies against hepatitis B core antigen (anti-HBc). People positive for either one are disqualified on the basis of evidence of ongoing or past infections. Such practice is feasible in developed countries in which hepatitis B infection rate is low. In contrast, in developing countries, like the Taiwan, where hepatitis B is endemic, about 90% of adults have anti-HBc antibody, indicating either past or ongoing hepatitis B infections. Therefore new screening method is needed. With the advent of new viral detection technology, especially the NAT, around 10-30％ of people with past hepatitis B infection seronegative for HBsAg actually harbored viral DNA in their blood or blood cell. Even in people positive for anti-HBs and anti-HBc, a conventional criteria for recovery from past hepatitis B infection, there are still 1-10％ reported positive for HBV DNA by NAT, though at a very low titer. It is imperative to know among blood donors qualified by current hepatitis B serologic screening protocol, the prevalence of seropositivity for HBV DNA. The result is also very important to re-evaluation develop blood screen strategy, to improve the safety of blood transfusion in Taiwan. Our data showed that our in-house assay is very sensitive（95％ detect limit：10 IU/ml）, and the positive rate for HBsAg negative blood donation is 0.18％.