Point-of-care end-tidal carbon monoxide reflects severity of hemolysis in sickle cell anemia

Abstract

Carbon monoxide (CO) production from heme catabolism is increased with hemolysis. A portable end-tidal CO (ETCO) monitor was used to analyze breath samples in 16 children with sickle cell anemia (SCA, 5-14 years). Median (range) ETCO for SCA was 4.35 ppm (1.8-9.7) versus 0.80 ppm (0.2-2.3) for controls (P < 0.001). ETCOc >2.1 ppm provided sensitivity and specificity of 93.8% (69.8-99.8%) for detecting SCA. ETCO correlated with reticulocytosis (P = 0.015) and bilirubin (P = 0.009), and was 32% lower in children receiving hydroxyurea (P = 0.09). Point-of-care ETCO analysis may prove useful for non-invasive monitoring of hemolysis and as a screening test for SCA.

Keywords: hemoglobinopathies; red blood cell disorders; sickle cell anemia.

Figure 1

(A) End-tidal carbon monoxide concentration in children with sickle cell anemia (SCA) and healthy age-matched controls (n=16 for both groups). Whiskers extend from 10-90^th percentile (+: mean). (B) Receiver-operator characteristic curve (solid line) for ETCOc in children with or without a diagnosis of SCA. A threshold ETCOc value of 2.1 ppm provided a sensitivity and specificity of 93.8% to differentiate between the two groups. (Dotted line: line of identity).

Figure 2

Association of end-tidal carbon monoxide concentration (ETCOc) with absolute reticulocyte count (Figure 2A, n=15), and serum bilirubin concentration (Figure 2B, n=12).