Comparison of Exhaled Nitric Oxide, Serum Eosinophilic Cationic Protein, and Soluble Interleukin-2 Receptor in Exacerbations of Pediatric Asthma Miguel J. Lanz, MD, 1,2 Donald Y.M. Leung, MD, PhD, 1,2 David R. McCormick, MS, 4 Ronald Harbeck, PhD, 5 Stanley J. Szefler, MD, 1 and Carl W. White, MD 1,3 * Summary. The hypotheses tested in this study were that during acute asthma exacerbations (1) exhaled nitric oxide concentrations [eNO] are a more sensitive, noninvasive indicator of asthma disease activity than serum markers of inflammation such as eosinophil cationic protein (ECP) or soluble interleukin 2 receptor (sIL2R), and (2) elevated [eNO] are reduced after treatment with glucocorticoids (GC). Peak eNO levels were measured by chemiluminescence during slow expiration. Seven asthmatic subjects (mean age 11 yrs; mean morning FEV1 65% predicted) receiving inhaled GC, and with no radiographic evidence of acute sinusitis, were studied before and after a course of oral GC. Measurements of [eNO], ECP and sIL2R levels, and FEV1% were obtained before and after a course of GC. Six atopic nonasthmatic subjects (mean age 12 years; mean FEV1 94% predicted) and seven normal subjects (mean age 13 years; mean FEV1 100% predicted) were studied. The mean peak [eNO] level (parts per billion: ppb) for the asthma subjects before treatment (52 ± 5 ppb SEM) was greater than the value for both nonasthmatic atopic and normal subjects (16 ± 2 ppb and 14 ± 2 ppb SEM, respectively; P < 0.0001). There was no significant difference in ECP or sIL2R values between asthmatic subjects and either atopic or normal subjects (P > 0.05). Baseline pre-GC treatment ECP levels in the asthmatic subjects were significantly higher (P < 0.002) than post-GC treatment values. The mean peak [eNO] level in the asthmatic subjects declined after oral GC treatment to 14 ± 1 ppb (P < 0.0002) and was less than 2 ppb different from either control group (P > 0.75). We conclude that [eNO] is a more sensitive marker of asthma disease activity than ECP and sIL2R levels. In addition, [eNO] appears to be a more useful indicator of the beneficial response to GC therapy than these other measurements in pediatric asthma. Pediatr. Pulmonol. 1997; 24:305–311. © 1997 Wiley-Liss, Inc. Key words: asthma; corticosteroids; treatment; inflammation; cytokines; nitric oxide. 1 Department of Pediatrics, National Jewish Medical and Research Center and University of Colorado Health Sciences Center, Denver, Colorado. 2 Division of Allergy/Immunology, National Jewish Medical and Re- search Center and University of Colorado Health Sciences Center, Denver, Colorado. 3 Division of Pediatric Pulmonology, National Jewish Medical and Re- search Center and University of Colorado Health Sciences Center, Denver, Colorado. 4 Department of Biostatistics, National Jewish Medical and Research Center, Denver, Colorado. 5 Department of Medicine, National Jewish Medical and Research Cen- ter, Denver, Colorado. Presented in part at the annual meeting of the American Academy of Asthma, Allergy and Immunology, San Francisco, CA, February 1997. Contract grant sponsor: National Jewish Center Clinical Investigation Committee; Contract grant sponsor: National Institutes of Health, con- tract grant number: HL36577, HL46481, MO1RR0051. *Correspondence to: Dr. Carl W. White, National Jewish Medical and Research Center, 1400 Jackson Street, Denver, CO 80206. E-mail: whitec@njc.org Received 2 April 1997; accepted 9 August 1997. Pediatric Pulmonology 24:305–311 (1997) Original Articles © 1997 Wiley-Liss, Inc.