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Cerebrospinal fluid rhinorrhea diagnosis

difference. 11 It also carries very little risk of harm to the patient because the test is noninvasive, consisting simply of collecting a sample of nasal rhinorrhea to send for test ing. Given that many patients have to collect these samples over time, Bleier et al. 26 assessed the reliability of the beta-2 transferrin assay in CSF samples from 6 patients stored in the refrigerator or at room temperature over 7 days. There were no adverse effects on the accuracy of the test regardless of storage temperature. All of these studies verify the beta-2 transferrin testing results with other modalities, such as IF, cisternography, or even clinical history based on chart review. These modali ties have their own limitations, however, making it difficult to know the exact accuracy of beta-2 transferrin testing. The consistently high sensitivities and specificities in mul tiple studies, as well as the fact that it is noninvasive and inexpensive, support it as a very reliable and cost-effective test for the confirmation of CSF leak (Supporting material 4). 14, 20–25, 27 Aggregate grade of evidence: C (Level 3: 8 studies; Level 4: 1 study); Benefit: Noninvasive, highly accurate test; Harm: Delay in diagnosis due to the need to perform the test in a specialty laboratory; Cost: $37.90; Benefits-harm assessment: Preponderance of benefit over harm; Value judgments: Preference for high accuracy in diagnosis prior to further intervention. Low level of evidence; Recommendation level: Recommendation for; Intervention: Using beta-2 transferrin testing for diagnosing CSF leaks. Beta trace protein Similar to beta-2 transferrin, beta trace protein is also present in high concentrations in the CSF, produced pri marily in the leptomeninges and choroid plexus. Seven ar ticles pertinent to beta trace protein testing in the setting of possible CSF leak were identified. One of these 7 was a case-control study, and 6 were cross-sectional studies. The sensitivity and specificity of beta trace protein testing reported from these studies ranges from 91% to 100% and 86% to 100%, 19, 22, 28–30 rivaling beta-2 transferrin in its accuracy. In the McCudden et al. 22 study, the 100% and 86% sensitivity and specificity reported for beta trace protein immunoassay was superior to the 87% to 100% sensitivity and 71% to 94% specificity of beta-2 transferrin. Because beta trace protein is present in both the blood and CSF, only at vastly different concentrations, blood lev els can affect CSF levels, and therefore the accuracy of beta trace protein testing. Meco et al. 31 noted that renal insuf ficiency and bacterial meningitis greatly increase and de crease CSF levels of beta trace protein, respectively, and therefore the test should not be used in these population groups. Apart from this, the study reported that beta trace protein was a more sensitive test than beta-2 transferrin, as

did 2 other studies. 22, 30 Other reported benefits of the test include its low cost at $20, 31 as well as its quick turnaround time, requiring less than 15 minutes for completion with the nephelometric assay. 19, 31 Although beta trace protein is not typically used in the United States, these studies indicate that this screening method merits consideration. This is particularly true con sidering it could offer potential benefits such as even lower cost and faster results with comparable accuracy to beta-2 transferrin (Supporting material 5). 19, 22, 28–32 Aggregate grade of evidence: C (Level 3: 6 studies; Level 4: 1 study); Benefit: Noninvasive, highly accurate test; Harm: Delay in diagnosis due to the need to perform the test in a specialty laboratory; limited availability in the United States; Cost: Low; Benefits-harm assessment: Preponderance of benefit over harm; Value judgments: Highly reliable test for the confirmation of CSF leak is important prior to further intervention; Recommendation level: Recommendation for; Intervention: Using beta trace protein testing for diagnosing CSF leaks. Radionuclide cisternography RNC is a nuclear medicine study in which a radioisotope is injected intrathecally via lumbar puncture, and pledgets are placed in the nasal cavities for several hours at a time, then removed and measured for radioactive tracer. This study may be able to better detect a CSF leak that is too slow or intermittent to produce a sufficient sample for beta-2 transferrin testing. It is an invasive study, however, and therefore carries the potential risks inherent to any other lumbar puncture with intrathecal injection. RNC is con sidered a diagnostic or confirmatory study rather than a localization study. The tracer may exit the skull base at the location of the fistula but contact the pledget at a sec ond separate site. In addition, it cannot guarantee that the CSF is from a rhinologic leak and not an otologic leak that has traveled down the Eustachian tube into the nasopharynx. Following the standard search of the 3 databases, a total of 5 studies were relevant to the use of RNC for the diag nosis of CSF leak and were included in this review. Four of these are cross-sectional studies, and 1 is a case series. These studies report a sensitivity of 76% to 100%, 24, 33, 34 a specificity of 100%, 24 and an accuracy of 90%. 24 Zapalac et al. 24 also report a cost of RNC of $2800. Because of its high cost, the fact that it has a lower sensitivity than beta-2 transferrin, and that it is invasive, they recommend beta-2 transferrin be repeated if necessary prior to proceeding with RNC for CSF leak confirmation. A localization study will likely still be necessary following confirmation with RNC. Although the level of evidence is rather low, the avail able data indicate that this is a more invasive, more

International Forum of Allergy & Rhinology, Vol. 6, No. 1, January 2016

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