Beta-2 Transferrin May Not Be Specific for Presence of Cerebrospinal Fluid in Middle Ear Fluid

Objective: Quantify beta-2 transferrin (B2T)-positivity in the middle ear fluid of patients undergoing pressure equalization tube (PET) placement for recurrent acute otitis media (RAOM) or chronic otitis media with effusion (COME). Study design: Prospective. Setting: Tertiary referral center. Patients: Eighty-one ears from 60 patients undergoing PET placement. Mean age was 12.1 years. Forty-three ears (60.6% of ears) were male. Forty-five ears (63.4%) had COME. Mean effusion duration was 6.2 months. Interventions: PET placement. B2T was measured in middle ear aspirates using quantitative ELISA. Ten ears were excluded due to coefficients of variance >20% between duplicate wells, likely from sample viscosity. Main outcome measures: B2T-positivity rate and quantitative levels. Results: Of 71 ears, 55 (77.5%) were B2T-positive. Compared with B2T-negative ears, B2T-positive ears were more likely to be younger (6.1 vs. 32.9 y, P =0.004), have mucoid effusion (70.9% vs. 20.0%, P =0.001), and have RAOM (45.6% vs. 12.5%, P =0.02). Fifty-three of 61 pediatric ears (86.9%) were B2T-positive, compared with 2 of 10 adult ears (20%). B2T-positivity was not associated with gender, effusion duration, or color of aspirate. No patients had chronic otorrhea after PET placement. Conclusions: Although B2T is considered the gold standard to detect cerebrospinal fluid (CSF), our study shows high B2T positivity rates in the middle ear fluid of patients undergoing PET placement for RAOM or COME. B2T may not be specific for CSF leak into the middle ear. Clinicians should exercise caution when interpreting results of B2T testing, particularly in the pediatric population and those with mucoid effusions.