Hepatitis B: isses in abaty diagnsis and vainatin
David Siebet, Mibigy egista, ya hiden's Hspita, Mebne; and Stephen anini, Vitian Infetis Diseases efeene abaty, Mebne
Intdtin
In Astaia, amst 1% f the ppatin may be hniay infeted with hepatitis B vis (HBV). This ests in p t 1200 deaths annay.1 The highest aiage ates ae in indigens pepe (10-25%), Minesian and Sth-East Asian immigants (5-15%) and pepe fm Sth-East Epe (2-5%). Despite the existene f an estabished matena seening and infant vainatin pgam, it has been vitay impssibe t identify pepe at isk befe thei expse t the vis. Vainatin aimed at high-isk gps has theefe faied t signifianty ede the bden f hni infetin in w pevaene nties ike Astaia.1 F these easns, a new pgam f nivesa vainatin has eenty been emmended.2
Via stte and pdts
Hepatitis B vis is a mpat 42 nm sphee (Fig. 1). The te envepe is mpsed f nits made fm hepatitis B sfae antigen (HBsAg) pteins, abhydates and ipids. Beneath this te aye is fnd the e, a 27 nm patie, made f ptein sbnits aed hepatitis B e antigen (HBAg).
The hepatitis B e antigen (HBeAg) is nt a stta mee; hweve, me than tw thids f its amin aid seqene is identia t that f the e ptein. It an be seeted fm hepatytes diety int bd as a sbe ptein3, whih is thght t pmte and maintain pesistent infetin.
Ate hepatitis B infetin
HBV is aqied by ntat with bd bdy fids ntaining infetis vis. Infetivity has ny been eay shwn f bd, genita seetins and, n asin, saiva. The inbatin peid anges fm 6-26 weeks with an aveage f 12 weeks (Fig. 2).
Fig. 1
A mde f hepatitis B vis.
Nte the 3 mpnents f sfae antigen pe-S1, pe-S2 and S.
Fig. 2
A gaphi epesentatin f segia events in ate hepatitis B.
Maj makes, hepatitis B sfae antigen (HBsAg) and
anti-hepatitis B e IgM (anti-HB IgM) ae in bd.
AT - aanine amintansfease
Tta anti-HB = anti-HB IgM + IgG
abaty diagnsis (Tabe 1)
HBsAg fist appeas in the bd ding the inbatin peid, whie the vis is ativey `epiating' in ive es. The antigen is pded in vast exess s that it is nt ny assiated with new infetis vis paties, bt as s in the sem as sma nn-infetis spheia and fiaments fms. In ate infetin, the HBsAg say disappeas within 3 mnths f nset. The HBeAg and HBV DNA an as be deteted in bd whie the vis is ativey epiating in the ive (Fig. 2). Symptms say appea as the nentatins f biibin, aanine amintansfease and eah f the maj via mpnents peak in the sem. These events inide with the fist appeaane f antibdies t HBV pteins (Fig. 2).
Antibdy t HBAg (anti-HB) ises fist. As a geneaisatin, the detetin f IgM antibdy speifi t the hepatitis B e is the pimay indiat f ate infetin. It say appeas at jst befe the nset f symptms and emains detetabe f at east 6 mnths. The IgG mpnent f anti-HB say pesists f ife.
Anti-HBe is the send antibdy t appea and is assiated with the apid eaane f HBeAg. ate, anti-HBe deines and pesists f ny a few mnths yeas if thee is n ative via epiatin.
The antibdy t HBsAg, anti-HBs, may nt beme detetabe f 3-6 mnths afte ate infetin. It is assiated with estin f the iness. This antibdy is egnised as the make f immnity t HBV.
Thee is a ange f vaiatins in the segia pfie and when in dbt an expet pinin an be sght. F exampe, in sme patients wh ea HBsAg and eve iniay, the anti-HBs antibdy may ny be pesent at w eves emains bew the eve f detetin.
hni hepatitis B infetin
Between 1% and 10% f infeted adts and de hiden devep hni infetin. Adts wh devep hni HBV ae nt say immnsppessed, bt when they ae, hni infetin is mmn. Me than 85-95% f newbns and hiden infeted nde the age f 3 yeas, bn t HBeAg psitive mthes, beme hni aies. This is thght t bease f the immngia immatity in the hid and the effet f matena HBeAg in te. Thse aies infeted in eay ife have an ineased isk f bth hni pesistent and hni ative hepatitis.
abaty diagnsis (Tabe 2)
Fm a abaty pespetive, hni infetin is defined as the pesistene f HBsAg in the bd f a peid f 6 mnths me. The segia pite depends n the degee f via ativity in hniay infeted hepatytes (Fig. 3).
A eenty infeted hni aie wi shw evidene f nging via epiatin in ive es. HBeAg and HBV DNA an be deteted in bd f mnths yeas afte ate infetin. High eves f anti-HB IgM antibdy ae n nge pesent.
Pepe with ng-standing HBV infetin may eventay ente a phase f w eve via epiatin. T ahieve this, hni aies mst ea HBeAg and HBV DNA fm the bd by ativey pding anti-HBe antibdy and eaing via DNA fm infeted ive es, msty via e mediated immnity.3 Sevea abtive attempts t ea HBeAg may ve many yeas and `faes' f ative hepatitis an (with witht symptms) nti anti-HBe is eventay made (Fig. 3). Patients wh annt ea the vis fae pesistent ative hepatitis and ae at a vey high isk f the devepment f ihsis and hepatea ainma.