Following the success of the CAVD-VIMC Elispot comparison study, the CAVD-VIMC ELISpot Assay Transfer study was designed to evaluate the transfer of the ELISpot assay SOP from IAVI CL to NVITAL. Assay results for the parent SOP (IAVI) from the comparison study will be used as golden standards to compare to those for the transferred SOP (NVITAL) obtained in this transfer study. The two co-primary objectives of this study are to ensure 1) the proportions of positive responders are equivalent; and 2) the positivity calls on the same set of specimens are concordant between the two assays.

Based on previous data from the comparison study, sample size calculations showed that satisfactory statistical power can be achieved if the true proportion of concordance is at least 90% when the true difference in response rates is no more than 6% based on a sample size of 150. To allow for an early look of futility, an interim analysis at n=75 was conducted to address possibly stopping the testing early due to un-equivalence.

Results from the interim analysis showed that both acceptance criteria on response rates and positivity calls were met. Specifically, the 95% C.I. on the difference in response rates is contained in the pre-specified equivalence margin of interval -15% and 15% (i.e., (-2.8%, 2.8%) for CMV and (-1.6%, 13.0%) for FEC responses); the lower bound of the 95% score confidence interval on the proportion of concordant positivity calls is greater than the pre-specified margin of 70% (i.e., 94.7% for CMV and 82.1% for FEC responses).  We expect to present the final study results at the time of presentation, if accepted.

The interim analysis of the transfer study allowed for an early look of futility and helped to identify sources of any possible differences between the parent and the transferred SOP. Valuable resources have been saved.