Fast and accurate spectrum sensing is crucial in realizing a reliable cognitive network. Cooperative spectrum sensing can help reducing the mean detection time and increasing the agility of the sensing process. However, when the number of cognitive users is large, the bandwidth need for the control channel that are used to report the secondary user nodes' results to the fusion center may become excessively large. In this paper, we apply the sequential probability ratio test (SPRT) to control the average number of the reporting bits. It is shown that the proposed technique not only reduces the mean detection time and bandwidth but also outperforms its non-sequential counterpart. We derive the relationships amongst the global performance, miss probability and false alarm probability and show how to control the average number of reports by thresholding the distributed cognitive users.