====== Beta-2 transferrin ======
Beta-2 transferrin is a carbohydrate-free (desialated) isoform of [[transferrin]], which is almost exclusively found in the [[cerebrospinal fluid]]. It is not found in blood, mucus or tears, thus making it a specific marker of [[cerebrospinal fluid]], applied as an assay in cases where [[Cerebrospinal fluid fistula]] is suspected.

Beta-2 transferrin would also be positive in patients with perilymph fluid leaks, as it is also present in inner ear perilymph. Thus, beta-2 transferrin in [[otorrhea]] would be suggestive of either a Cerebrospinal fluid fistula or a perilymph leak.
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The effect of time and temperature on [[beta-2 transferrin]] stability in [[cerebrospinal fluid]] (CSF) is not well established. After collecting nasal CSF for testing, beta-2 transferrin has been found to be stable and detectable for 1 week, whether being refrigerated or stored at room temperature. The purpose of a study was to determine if beta-2 transferrin remained detectable longer than 1 week and whether refrigeration improved its detectability.

In patients undergoing therapeutic CSF diversion, 2-mL CSF samples were collected from 18 patients. The samples were divided and stored either at room temperature, or at 4°C, and tested for beta-2 transferrin at 7 and 14 days. CSF was collected from external ventricular drains (EVDs) (n = 15), lumbar drains (n = 2), and subdural drains (n = 1).

Of the 18 CSF samples originally testing positive for beta-2 transferrin, none turned negative at 7 or 14 days, in both the refrigerated and room temperature groups (95% confidence interval [CI], 0% to 18.5%).

Beta-2 transferrin remained detectable for 14 days in all CSF samples, regardless of being stored at 4°C or room temperature
((Zervos TM, Macki M, Cook B, Schultz LR, Rock JP, Craig JR. Beta-2 transferrin 
is detectable for 14 days whether refrigerated or stored at room temperature. Int
Forum Allergy Rhinol. 2018 May 3. doi: 10.1002/alr.22136. [Epub ahead of print]
PubMed PMID: 29722921.
)).