Modification analysis is part of most maintenance processes and includes among other activities, early prediction of potential change impacts, feasibility studies, cost estimation, etc. Existing impact analysis and regression testing techniques being source code based require at least some understanding of the system implementation. In this research we present a novel approach that combines UCM with FCA to assist decision makers in supporting modification analysis at the requirements level. Our approach provides support for determining the potential modification and re-testing effort associated with a change without the need to analyze or comprehend source code. We demonstrate the applicability of our approach on a telephony system case study.