Method for distinguishing disruptions of the flow resistance in a blood treatment system which comprises the following steps: a) measuring at least three pressure signals selected from the group comprising (PB1, PB2, PD1, PD2) which are measured on at least three pressure sensors which are selected from the group comprising,, and, wherein refers to the pressure sensor in the blood circulation upstream of the blood inlet in the tangential flow filter TFF and PB1 refers to the pressure measured at the pressure sensor, refers to the pressure sensor in the blood circulation downstream of the blood outlet from the tangential flow filter TFF and PB2 refers to the pressure measured at the pressure sensor, refers to the pressure sensor in the dialysate circuit upstream of the dialysate inlet in the tangential flow filter TFF and PD1 refers to the pressure measured at the pressure sensor and refers to the pressure sensor in the dialysate circuit downstream of the dialysate outlet from the tangential flow filter TFF and PD2 refers to the pressure measured at the pressure sensor; b) calculating the quotients and/or the differences from the pressure signals measured according to step a), wherein the quotients and/or differences are calculated from the pressure signals selected from the group comprising (PB1, PB2) and/or (PB1, PD1) and/or (PB1, PD2) and/or (PB2, PD1) and/or (PB2, PD2) and/or (PD1, PD2) and/or (PB1, PDM) and/or (PB2/PDM) and/or (PD1, PBM) and/or (PD2, PBM) and/or (PDM, PBM) in a central processing unit, wherein PBM or PDM refers to the respective mean value from (PB1, PB2) or (PD1, PD2); c) at least one occurrence of time-delayed repetition of the steps a) and b), wherein a measurement operation is carried out at the same at least three pressure sensors as in the previous measurement and from the measured pressure signals the same quotients and/or differences are calculated; d) producing at least one time trend from the measured pressure signals selected from the group comprising (PB1, PB2, PD1, PD2) and/or the calculated differences or quotients of the pressure signals (PB1, PB2) and/or (PB1, PD1) and/or (PB1, PD2) and/or (PB2, PD1) and/or (PB2, PD2) and/or (PD1, PD2) and/or (PB1, PDM) and/or (PB2, PDM) and/or (PD1, PBM) and/or (PD2, PBM) and/or (PDM, PBM); e) evaluating the at least one time trend, whether a change of the at least one time trend beyond a tolerance range has occurred; f) producing a pattern for the evaluation of the at least one time trend; g) associating the pattern with an interference image and h) indicating the interference on a display device of the central processing unit. a) measuring at least three pressure signals selected from the group comprising (PB1, PB2, PD1, PD2) which are measured on at least three pressure sensors which are selected from the group comprising,, and, wherein refers to the pressure sensor in the blood circulation upstream of the blood inlet in the tangential flow filter TFF and PB1 refers to the pressure measured at the pressure sensor, refers to the pressure sensor in the blood circulation downstream of the blood outlet from the tangential flow filter TFF and PB2 refers to the pressure measured at the pressure sensor, refers to the pressure sensor in the dialysate circuit upstream of the dialysate inlet in the tangential flow filter TFF and PD1 refers to the pressure measured at the pressure sensor and refers to the pressure sensor in the dialysate circuit downstream of the dialysate outlet from the tangential flow filter TFF and PD2 refers to the pressure measured at the pressure sensor; b) calculating the quotients and/or the differences from the pressure signals measured according to step a), wherein the quotients and/or differences are calculated from the pressure signals selected from the group comprising (PB1, PB2) and/or (PB1, PD1) and/or (PB1, PD2) and/or (PB2, PD1) and/or (PB2, PD2) and/or (PD1, PD2) and/or (PB1, PDM) and/or (PB2/PDM) and/or (PD1, PBM) and/or (PD2, PBM) and/or (PDM, PBM) in a central processing unit, wherein PBM or PDM refers to the respective mean value from (PB1, PB2) or (PD1, PD2); c) at least one occurrence of time-delayed repetition of the steps a) and b), wherein a measurement operation is carried out at the same at least three pressure sensors as in the previous measurement and from the measured pressure signals the same quotients and/or differences are calculated; d) producing at least one time trend from the measured pressure signals selected from the group comprising (PB1, PB2, PD1, PD2) and/or the calculated differences or quotients of the pressure signals (PB1, PB2) and/or (PB1, PD1) and/or (PB1, PD2) and/or (PB2, PD1) and/or (PB2, PD2) and/or (PD1, PD2) and/or (PB1, PDM) and/or (PB2, PDM) and/or (PD1, PBM) and/or (PD2, PBM) and/or (PDM, PBM); e) evaluating the at least one time trend, whether a change of the at least one time trend beyond a tolerance range has occurred; f) producing a pattern for the evaluation of the at least one time trend; g) associating the pattern with an interference image and h) indicating the interference on a display device of the central processing unit.