Transcutaneous CO-oximetry differentiates asthma exacerbation and convalescence in children

• Published in: Journal of allergy and clinical immunology Vol. 142; no. 2; pp. 676 - 678.e5
• Main Authors: Kantor, David B., Petty, Carter R., Phipatanakul, Wanda, Gaffin, Jonathan M.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.08.2018; Elsevier Limited
• Subjects: Asthma; Biomarkers; Carbon monoxide; Children; Children & youth; Convalescence; Enrollments; Hispanic people; Tobacco smoke
• ISSN: 0091-6749; 1097-6825; 1097-6825
• DOI: 10.1016/j.jaci.2018.02.048

To the Editor: There is a paucity of inflammatory biomarkers for asthma exacerbation, and current options require patient effort or discomfort and have not significantly affected management.1 Biologic production of carbon monoxide (CO) as a result of hemeoxygenase-1 upregulation in response to oxidative stress2 has been associated consistently with asthma activity.3 Increased levels of exhaled breath condensate CO and arterial carboxyhemoglobin are associated with loss of control and decrease with appropriate steroid therapy.4-6 In this context we tested whether pulse CO-oximetry (carbon monoxide percent saturation of hemoglobin [SpCO]) is associated with asthma exacerbation in a prospective observational cohort.7 Children aged 6 to 17 years with a history of physician-diagnosed asthma were enrolled during an emergency department visit for acute asthma exacerbation and returned 6 weeks later for a follow-up research visit (ie, the convalescent visit) when they had returned to symptomatic baseline (see Fig E1 in this article's Online Repository at www.jacionline.org). Eight (14%) subjects had frequent environmental tobacco smoke exposure (see Table E1 in this article's Online Repository at www.jacionline.org). There was a significant difference between exacerbation and convalescent mean SpCO values (6.02% ± 2.8% vs 3.42% ± 2.0%, P < .0001). [...]evaluation of each subject's mean SpCO regression (Fig 1) demonstrated that nearly all subjects had a negative slope (decreasing SpCO value) between exacerbation and convalescence. Characteristic Primary cohort (n = 59) SICAS-2 (n = 108) P value Male sex, no. (%) 34 (58) 63 (58) Age (y), mean (SEM) 11.0 (0.44) 7.7 (0.21) <.001 Race, no. (%) .12 White, non-Hispanic 9 (15) 13 (12) Black, non-Hispanic 22 (37) 32 (30) Hispanic 23 (39) 61 (56) Other 4 (7) 2 (2) Household income <$50,000 29 (49) 43 (40)∗ .24 Environmental tobacco smoke, no. (%) .79 Never 25 (42) 40 (37) Rarely 17 (29) 31 (29) Several times per month 2 (3) 8 (7) Several times per week 4 (7) 8 (7) Daily 8 (14) 19 (18) FEV1 (% predicted), mean (SEM) 109.6 (2.3) 98.6 (1.7) <.001 FEV1/FVC × 100, mean (SEM) 83.2 (2.2) 84.2 (0.6) .58 Aeroallergen sensitization 48 (91) 64 (60) <.001 Table E1 Selected characteristics of subjects Cut point Sensitivity Specificity Correctly classified ≥2 91.53% 13.56% 52.54% ≥3 89.93% 44.07% 66.95% ≥4 81.36% 67.80% 74.58% ≥5 61.02% 81.36% 71.19% ≥6∗ — — — ≥7 38.98% 94.92% 66.95% ≥8 23.73% 96.61% 60.17% ≥9 11.86% 96.61% 54.24% Table E2 Performance of SpCO measurement to differentiate exacerbation from convalescent visits