Devices and methods are provided for the detection of CSF in a biological sample. In certain embodiments the device is a lateral flow device comprising: a porous substrate; a sample addition zone disposed on or in said porous substrate; a detection zone disposed on or in said porous substrate where said detection zone comprises at least a first test line (T1) and a second test line (T2) each test line comprising binding moieties that bind a complex formed between beta-trace protein (βTP) and an indicator attached to a βTP binding molecule; wherein said porous substrate defines a flow path through which a sample applied to the sample addition zone flows under capillary action away from said sample addition zone into said detection zone; and wherein said first test line (T1) and said second test line (T2) are is configured so that either no test line signal or just a signal at the first test line (T1) is detectable when βTP concentration in a sample applied to said device is lower than the βTP level indicative of a CSF leak; and said second test line (T2) is configured so that a signal is detectable at said second test line when βTP concentration in a sample applied to said device is greater than the βTP level indicative of a CSF leak.