Assay for rapid detection of cerebrospinal fluid leaks

A method of detecting the presence of cerebrospinal fluid in a liquid biological sample comprising:

• a) distributing the liquid biological sample on to a sample pad of a lateral flow device which comprises, in lateral flow sequence:
• a sample pad, a conjugate pad, a binding portion, and an absorbent pad, so as to permit the sample to flow along the lateral flow device;
• and wherein:
• (i) the conjugate pad thereof, downstream in lateral flow from the sample pad, comprises both (A) and (B) thereon, wherein:
• (A) is a first plurality of transferrin-binding antibodies conjugated to a first plurality of nanoparticles, and
• (B) is a plurality of lectin molecules conjugated to a second plurality of nanoparticles;
• (ii) the binding portion thereof, downstream in lateral flow from the conjugate pad, comprises the following separate domains:
• a. a domain which comprises a second plurality of transferrin-binding antibodies which are adhered to a surface of the lateral flow device;
• b. a dried blood serum domain reagent adhered to a surface of the lateral flow device;
• b) determining an intensity of an optical signal present at domain (ii)(a) and also at domain (ii)(b);
• c) calculating an optical value, wherein the optical value is determined as =(T1 intensity)2×(T2 intensity), wherein T1 intensity is the optical signal intensity at domain (ii)(a), and T2 intensity is the optical signal intensity at domain (ii)(b), and determining if the optical value is above or below a pre-determined cut-off value for the lateral flow device, wherein if the optical value is above the predetermined cut-off value for the lateral flow device then the sample is identified as containing cerebrospinal fluid, and wherein if the optical value is below the pre-determined cut-off value for the lateral flow device then the sample is identified as not containing cerebrospinal fluid.