Elevated erythrocyte carbonic anhydrase activity is a novel clinical marker in hyperventilation syndrome

Background: The aim of this study was to evaluate the erythrocyte carbonic anhydrase (CA) activity in patients with hyperventilation syndrome. Methods: A total of 71 patients with hyperventilation syndrome and 60 controls were recruited in this study for measurement of the erythrocyte CA activity. CA activity was analyzed from erythrocyte using CA esterase activity analysis. Results: The erythrocyte CA activity was significantly elevated in the patients with hyperventilation syndrome compared to controls (31.07 +/- 1.37 U/g Hb vs. 24.67 +/- 0.99 U/g Hb, p=0.003). The standardized beta value and significant R-2 value of total CA activity for prediction of hyperventilation was 0.155 (p=0.016) and 0.024, respectively. Moreover, a significant negative correlation was found between total CA activity and partial pressure of carbon dioxide (PaCO2) (r=-0.185, p=0.03, n=131). Furthermore, the adjusted odds ratios for patients with hyperventilation were 11.6 (95% CI: 4.8-27.9) and 51.0 (95% CI: 5.8-445.2) for individuals with either PaCO2 <= 28.1 mm Hg or CA activity >= 29.71 U/g hemoglobin (Hb), and for individuals with both PaCO2 <= 28.1 mm Hg and CA activity >= 29.71 U/g Hb, respectively, compared to individuals with both (PaCO2) 28.1 mm Hg and CA activity < 29.71 U/g Hb. Conclusions: Erythrocyte CA activity was significantly elevated in patients with hyperventilation. Detection of erythrocyte CA activity may provide a potential explanatory parameter for the prediction of hyperventilation syndrome. Clin Chem Lab Med 2009;47:441-5.