View PDF Version - RePub - Erasmus Universiteit Rotterdam
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Statistical analysis<br />
Early on-treatment prediction of response to PEG 109<br />
Sustained response (SR), the predefi ned primary endpoint in the original study, was<br />
defi ned according to the EASL guidelines as the combined presence of serum HBV<br />
DNA level below 10,000 copies/mL (1,714 IU/mL) and normalization of ALT at the end<br />
of follow-up (week 72). 20 The association between baseline factors and SR was assessed<br />
by univariate logistic regression analyses. Predictive values of early on-treatment serum<br />
HBsAg, as well as HBV DNA and ALT levels (weeks 4, 8, and 12) were explored applying<br />
logistic regression analysis techniques. Discrimination, which is the ability to distinguish<br />
patients who will develop SR from those who will not, was quantifi ed by the area under<br />
the receiver-operating characteristic curve (AUC). The best model-fi t was assessed comparing<br />
the AUC and the Akaike’s Information Criteria (AIC). Hereafter the optimal cut-off<br />
values for serum HBsAg and HBV DNA levels during treatment were established with<br />
the use of explanatory plots and the maximum chi-square approach to fi nd a clinically<br />
useful rule for (dis)continuation of therapy. 21 SPSS version 15.0 (SPSS Inc., Chicago, IL,<br />
USA) and the SAS 9.2 program (SAS Institute Inc., Cary, NC, USA) were used to perform<br />
statistical analyses. All statistical tests were two-sided and were evaluated at the 0.05<br />
level of signifi cance.<br />
RESULTS<br />
Sustained response rate<br />
Twenty-four (22%) of 107 patients developed SR. The number of sustained responders<br />
was comparable between the peginterferon alfa-2a monotherapy and the peginterferon<br />
alfa-2a and ribavirin combination therapy group (14 (26%) of 53 versus 10 (19%) of 54<br />
patients, respectively, p=0.33). The two treatment groups were therefore pooled for<br />
further analysis. Among the 24 sustained responders, one patient cleared HBsAg from<br />
serum and developed anti-HBs.<br />
Baseline characteristics<br />
Baseline characteristics of the 107 patients are shown in table 1. The mean pretreatment<br />
serum HBsAg level was 3.8 log IU/mL (range 1.1-5.0 log IU/mL) and the mean serum HBV<br />
DNA level was 6.8 log copies/mL (range 4.3-9.5 log copies/mL), both were stable during<br />
the screening period. There was no signifi cant correlation between serum HBsAg and<br />
other factors at baseline including serum HBV DNA and ALT, HBV genotype, age, gender,<br />
body mass index (BMI) or liver histology. Baseline characteristics were comparable