Use of alveolar carbon monoxide to measure the effect of ribavirin on red blood cell survival

A major side effect of ribavirin (RBV) treatment is anemia. While this anemia is thought to result from increased RBC turnover, RBC survival has not been determined in subjects receiving RBV due to the complexity of the techniques commonly used to quantitate RBC life span. We recently described a simple, rapid, non-invasive technique that utilizes measurements of alveolar carbon monoxide (CO) concentration to determine RBC survival. In the present report, this method was employed to assess RBC survival in patients receiving RBV for hepatitis C. Each of the 31 measurements of RBC survival in 12 subjects with RBV-associated anemia was below the lower limit of normal (77 days), and the average survival (46 ± 14 days) in these subjects was only about 38% of that of healthy controls (122 ± 23 days). Five hepatitis C patients not undergoing RBV treatment had normal RBC survivals (112 ± 17 days). While the mean reticulocyte percentage was significantly elevated in subjects treated with RBV, 59% of these measurements fell within the limits of normal. We conclude that RBV-associated anemia consistently is associated with reduced RBC survival as determined from breath CO measurements and that this reduced survival frequently is not associated with an elevated reticulocyte count.