Operation and validation of rapid diagnostic test kit for CSF leak detection

The schematic representation of the user steps for our developed diagnostic test kit is shown in Fig. 1. To determine whether a sample fluid contained CSF, the fluid was first absorbed into the collection swab. The swab was then inserted into the buffer in tube A and twirled around the edge of the tube for 10 s at 2 rotations per second in order to release the sample from the swab into the buffer. Tube A was then inverted 5 times to ensure the released sample was well-mixed. Next, 100 μL of the liquid in tube A was transferred to tube B using one of the provided disposable transfer pipettes. Tube B was then inverted 5 times to ensure complete mixing. The release of the sample from the swab into tube A and the subsequent transfer into tube B resulted in an overall 300-fold dilution of the original sample. Lastly, 100 μL of the solution in tube B was transferred into tube C where the barcode-style LFA test strip was also inserted. After 20 min, the results were interpreted where the formation of 0 and 1, 2, or 3 visible test lines indicated a diagnosis of negative, gray zone, or positive, respectively. Photographs of the test strips were taken by a Nikon D3400 digital camera (Nikon, Tokyo, Japan) in a controlled lighting environment.

Schematic representation of the procedure for operating our rapid diagnostic test kit for the detection of CSF leaks. (1) Swab with collected sample is dipped and twirled in tube A buffer to release sample. (2) Released sample from tube A is further diluted in tube B using disposable transfer pipettes and then transferred to tube C. (3) Barcode-style LFA test strip is inserted into the fluid in tube C for 20 min. (4) Test results are interpreted by the user.

We first evaluated the ability of our diagnostic test kit to detect for βTP by testing samples containing purified, recombinant βTP in PBS. Then we evaluated a variety of different patient samples collected at the Ronald Reagan UCLA Medical center which were either negative or positive for the presence of CSF. These included fluid collected from skull base sites during endoscopic transnasal transsphenoidal (TNTS) surgeries, superior semicircular canal dehiscence (SSCD) repair surgeries, and brain tumor resection surgeries. Rhinorrhea and otorrhea specimens from healthy volunteers and patients with suspected CSF leaks were also included (University of California Los Angeles [UCLA] Institutional Review Board approval 17–001065).