A downhole completion system includes a production casing installed in a borehole and an annular barrier system to be expanded in an annulus between a production casing and a wall of a borehole or another well tubular structure downhole for providing zone isolation between a first and second zones. An annular barrier has a tubular metal part adapted to be mounted as part of the production casing. The downhole completion system further includes a sensor device which is in communication with the first zone and/or second zone, respectively, the sensor device being adapted to measure the first pressure of the first zone and the second pressure of the second zone for verifying the zone isolation.