Nasal lavage concentrations of free hemoglobin as a marker of microepistaxis during nasal provocation testing

BACKGROUND: The constituents of nasal mucus may be contaminated by plasma if there is epistaxis. Gross epistaxis is apparent as a red lavage fluid, while microepistaxis may yield a clear fluid. If gross or microepistaxis are present, it will be difficult to decide whether plasma protein concentrations are elevated because of plasma exudation or bleeding. In order to discriminate between these two possibilities, we measured erythrocyte-derived free hemoglobin (fHb) in nasal lavage fluids. METHODS: Single-blinded subjects underwent standard hypertonic saline nasal provocation. Unilateral hypertonic nasal provocation was performed in normal, allergic rhinitis (AR) and nonallergic rhinitis (NAR) subjects (total of 1316 specimens). fHb was measured using the Sigma-Aldrich kit (St. Louis, MO). Grossly bloody specimens were analyzed separately from the remainder. Statistical analysis defined the means and 95th percentiles for fHb and albumin in the nonbloody normal group. RESULTS: fHb concentrations ranged from below the limits of detection (< 1 microg/ml) to > 164 microg/ml fHb was 79.3 microg/ml +/- 4.7 (mean +/- SEM) in four normal, 31 AR and 25 NAR grossly bloody specimens. The 95th percentile of fHb in the nonbloody normal samples (n = 68 subjects, n = 681 specimens) was 16.5 microg/ml. This value was defined as the threshold to detect potential microepistaxis, and corresponded to approximately 245 000 erythrocytes per ml of lavage fluid. Total protein (P < 0.05) and albumin (P < 0.001), but not markers of glandular secretion, were significantly increased in samples with fHb > 16.5 microg/ml compared to those < or = 16.5 microg/ml. Elevations of fHb without changes in albumin were more prevalent in nonallergic rhinitis. CONCLUSIONS: Significant bleeding into nasal lavage samples can contaminate the specimens and increase the concentrations of both fHb and plasma proteins. Increased albumin alone would indicate increased vascular permeability. The mechanism(s) leading to elevated fHb without increased plasma proteins require further investigation.