DIAGNOSTIC-VALUE OF ANTI-HEPATITIS-D VIRUS (HDV) ANTIBODIES REVISITED- A STUDY OF TOTAL AND IGM ANTI-HDV COMPARED WITH DETECTION OF HDV-RNA BY POLYMERASE-CHAIN-REACTION

A high serum titre (greater than or equal to 1000 or greater than or e qual to 5000) of total antibody to hepatitis D virus (anti-KDV) and po sitive for immunoglobulin (Ig)M anti-HDV have been used to represent H DV replication, while reverse transcription-polymerase chain reaction (RT-PCR) is currently the most sensitive assay for detecting HDV virae mia. The aim of the present study was to re-evaluate the correlation o f total anti-HDV and IgM anti-HDV with KDV viraemia based on RT-PCR an d to assess the clinical significance of these markers in acute and ch ronic KDV superinfection. Chronic HDV infection was defined as positiv e HDV-RNA by RT-PCR for more than 6 months, while total anti-HDV titre was defined by serial dilution. Of 178 hepatitis B virus (HBV) carrie r patients studied, 119 cases had been anti-HDV positive for more than 6 months. Two-thirds (79/119) were positive for HDV viraemia by RT-PC R. Only half the chronic HDV viraemic patients had a high titre (great er than or equal to 1000) of total anti-HDV, and there was only modera te agreement (kappa=0.41) between total anti-HDV titre/IgM anti-HDV an d HDV-RNA and chronic HDV viraemia. Based on cross-sectional and longi tudinal follow-up analyses, serum total anti-HDV titres greater than o r equal to 100 appeared to be an excellent cut-off titre (kappa=0.91) in differentiating chronic from acute HDV infection among viraemic pat ients. In summary, IgM and a high titre total of anti-HDV are not good markers of HDV viraemia, but an anti-KDV titre of greater than or equ al to 100 appears to be an excellent marker for the differentiation of acute from chronic HDV superinfection.