[Agreement between two devices for measuring exhaled nitric oxide]

[Diagnostic value of exhaled nitric oxide measurement in mild asthma]

OBJECTIVES

To assess the diagnostic value of fractional exhaled nitric oxide (FE(NO)) in mild asthma.

MATERIAL AND METHODS

Cross-sectional descriptive study in a group of patients with no history of respiratory or allergic illness (control group) and a group of patients with a history of mild asthma with no baseline treatment (asthma group), both aged 6 to 14 years. The following examinations were performed: measurement of FE(NO) using the portable NIOX MINO(®) device, allergy tests and spirometry. Repeatability of paired FE(NO) measurements was estimated with the intraclass correlation coefficient, the repeatability coefficient and the variation coefficient. The diagnostic value was assessed with the sensitivity, specificity, area under the ROC curve and positive likelihood ratio (LR+) for each cut-off point.

RESULTS

Eighty-seven patients were included in the control group and 57 in the asthma group. The mean FE(NO) value was 12.1 ppb (SD 13.5) in the control group and 42.9 ppb (SD 24.5) in asthmatics (P<.001). The intraclass correlation coefficient was 0.98 (95% CI: 0.96-0.99) and of 0.97 (95% CI: 0.92-0.99) in controls and asthmatics, respectively. The repeatability coefficient was 5.5 in controls and 9.2 in asthmatic children, and the median variation coefficient was 8.3% and 6.1%. The optimal cut-off value for FE(NO) was 19 ppb (sensitivity and specificity were 91.4% and 87.2%, respectively). The area under the ROC curve was 0.93 (95% CI: 0.88-0.97) (P<.001) and the LR+ was 7.1. Subclinical sensitisation to pneumoallergens accounted for most false positive cases.

CONCLUSIONS

The determination of FE(NO) with NIOX MINO(®) has an adequate repeatability, especially for healthy patients. For asthmatic patients we recommend determining the average of two measurements. The test has a high diagnostic value in mild asthma. Subclinical sensitisation to pneumoallergens can cause the FE(NO) value to rise to pathologic levels.

Association among lung function, exhaled nitric oxide, and the CAN questionnaire to assess asthma control in children

BACKGROUND

The aim of this study was to investigate the association among a validated symptom-based questionnaire for asthma control in children (CAN), forced expiratory volume in 1 sec (FEV(1)), and fractional exhaled nitric oxide (FE(NO)).

METHODS

Observational cross-sectional study was performed in a consecutive sample of asthmatic children aged between 7 and 14 years old from December 2007 to February 2008. FE(NO) was measured with a portable electrochemical analyzer and forced spirometry was performed according to American Thoracic Society/European Respiratory Society. The CAN questionnaire was completed by the parents (aged <9 years old) or by the children (> or = 9 years old). The strength of the association among FEV(1), FE(NO), and CAN questionnaire was studied using Spearman's rho, and the degree of agreement for asthma control among FEV(1), FE(NO), and CAN questionnaire, with classification of these variables according to values of normality, was studied using Pearson's chi(2) test and Cohen's kappa (KC).

RESULTS

We studied 268 children, mean age 9.7 +/- 2.1 years. Significant correlations were found between FE(NO) and CAN (r = 0.2), between FEV(1) and CAN (r = -0.3), and between FE(NO) and FEV(1) (r = -0.12). On classifying the variables according to values of normality, no agreement was found to establish the degree of asthma control between FE(NO) and CAN (KC = 0.18, chi(2) Pearson = 9.63); between FEV(1) and CAN (KC = 0.29, chi(2) = 38.5); or between FE(NO) and FEV(1) (KC = 0.07, chi(2) = 4.9).

CONCLUSIONS

The association among the three measurement instruments used to assess asthma control (FEV(1), FE(NO), and CAN) was weak. These are instruments that quantify variables that influence asthma in different ways, in this sense, none can be used instead of another in asthma management although they are complementary.

[Feasibility of FeNO measurement in asthmatic children in the primary care setting. CANON Study]

AIM

Asses the feasibility of exhaled nitric oxide (FeNO) measurement in asthmatic children using a hand-held device in the primary care setting.

METHODS

Multicentre study performed in the paediatric clinics in seven Spanish primary health care centres. Each centre consecutively included 6-14 year-old children with doctor-diagnosed asthma. Children were asked to obtain two valid measurements of FeNO with the hand-held device NIOX MINO (Aerocrine AB, Solna, Sweden). Feasibility analysis included: (a) percentage of children able to perform the manoeuvre, (b) time required to obtain a successful determination, (c) number of attempts needed, and (d) acceptability of the technical procedure by clinical personnel involved in their guidance.

RESULTS

The Study enrolled 151 children. A total of 149 (98.7%) were able to perform the FeNO manoeuvre. The majority (55%) of children had previous experience of using the hand-held device. The Overall median (and Interquartile Range, IQR) of attempts needed to reach a first valid measurement was 2 (1-3) and median (IQR) of time taken was 4 min (3-5). Nurses considered the overall procedure was very easy or easy in 87.8% (teaching) and 86.5% (performing) of children. Children with previous experience performed the manoeuvre in less attempts, less time and more easily than children without experience.

CONCLUSIONS

Measurement of FeNO using NIOX MINO device is technically feasible and acceptable for children and staff in the clinical context of asthma management in primary health care. Previous experience had a positive, learning effect, in teaching and performing the FeNO manoeuvre.

Exhaled nitric oxide measurements: correction equation to compare hand-held device to stationary analyzer

INTRODUCTION

Exhaled nitric oxide (FE(NO)) is a reliable non-invasive marker of airway inflammation. In 2003 FE(NO) chemiluminescence analyzer (NIOX; Aerocrine AB, Solna, Sweden) was approved by U.S. Food and Drug Administration for monitoring asthma therapy. Recently, the same company developed a portable device using electrochemical sensors (NIOX-MINO; Aerocrine AB). The aim of our study was to compare NIOX-MINO FE(NO) values to those obtained by NIOX and to calculate a correction equation.

METHODS

Two adequate measurements obtained by NIOX and NIOX-MINO were recorded in 32 subjects (16 females, mean age 41 years).

RESULTS

FE(NO) values measured by NIOX-MINO were systematically higher than those obtained by NIOX (47.1ppb, IC 95% 35.2-59.1 and 36.9ppb, IC 95% 25.0-49.0, respectively). There was a significant correlation (r=0.998, p<0.001) between FE(NO) measured by the two analyzers and the following conversion equation was calculated as: FE(NO(NIOX))=-1.656(SE=0.61)+0.808(SE=0.009)x FE(NO(NIOX-MINO)) DISCUSSION: FE(NO) values measured by the portable nitric oxide analyzer are reliable and strongly correlated with values obtained by the standard stationary device, with a systematic difference observed between the two instruments' values that can be described by the conversion equation we provided. This equation will help clinicians and researchers to compare data obtainable by the two analyzers.