Lower respiratory tract infections appear to be the most important risk factor for current asthma in subarctic schoolchildren.

AIM: The aim of this study was to identify possible risk factors for current asthma revealed by two studies in Northern Norway in 1985 and 2008 and to evaluate these factors contributing to the increased prevalence of asthma over these 23 years. METHODS: As part of the 'Asthma and allergy study among schoolchildren in Nordland county' we performed a case-control study (70.0% attendance) comparing 153 children with current asthma (cases) to their non-asthmatic controls. The results from this 2008 study were compared to a similar case-control study (93.2% attendance) performed in 1985 based on 62 current asthmatics. RESULTS: In 1985, the most important risk factors for current asthma were repeated lower respiratory tract infections (LRTIs) with adjusted odds ratio (aOR) 52.11, together with urticaria ever and atopic disease in the family. In 2008, the most important risk factors were food allergy with aOR 7.06, LRTIs during the first three years of life with aOR 5.80 and hospitalisation caused by LRTIs. CONCLUSION: In both studies, LRTI was the most important risk factor for current asthma. Whether or not LRTIs have contributed to the increased asthma prevalence in this population over 23 years remains unresolved.

The effect of exercise on exhaled nitric oxide depends on allergic rhinoconjunctivitis in children.

OBJECTIVE: Fractional exhaled nitric oxide (FENO) and exercise testing are widely used for the evaluation of pediatric asthma. The evidence relating to the effects of strenuous exercise on FENO in children is conflicting. Little information is available on the association between exercise and FENO in relation to allergic rhinoconjunctivitis (AR). We aimed to investigate the effects of AR on children's FENO in response to a standardized treadmill exercise test. METHODS: A total of 124 children with current asthma and 124 non-asthmatic children aged 8-16 years were studied. FENO was measured at baseline, at 1 and 30 min after an exercise challenge test using the single breath technique with EcoMedics Exhalyzer. A structured parental interview, spirometry, serum allergen-specific IgE and skin prick tests were performed. RESULTS: Baseline FENO was higher in both asthmatics and non-asthmatics with AR than without AR (both p < 0.001). The FENO time trend was dependent on AR (p = 0.039), irrespective of asthma (p = 0.876). In children with AR, FENO had declined at 1 min by a mean of 6.1 ppb with a 95% confidence level of 5.1-7.5 ppb; at 30 min, the reduction was 2.8 (2.5-3.3) ppb. In children without AR, at 1 min the decline in FENO was 2.7 (2.1-3.5) ppb and by 30 min post-exercise it was 1.6 (1.3-2.0) ppb. CONCLUSIONS: The impact of exercise on FENO was dependent on the allergic phenotype, regardless of asthma status. FENO decreased immediately after exercise, and did not return to baseline level within 30 min.

Validation of a questionnaire against clinical assessment in the diagnosis of asthma in school children.

AIM: A questionnaire has been used repeatedly in cross-sectional studies to determine the prevalence of asthma, allergic rhinoconjunctivitis (AR) and eczema among schoolchildren in Nordland County, Norway. The current study was designed to validate the questionnaire against clinical assessment as the diagnostic gold standard and to investigate the extent of possible misclassification. METHODS: A subsample of 801 schoolchildren of 4150, whose parents had answered a questionnaire covering asthma and atopic diseases, underwent a detailed clinical evaluation including a standardized interview, a clinical examination, skin prick tests (SPT), blood samples, spirometry an exercise treadmill test (EIB test) and measurement of exhaled nitrogen oxide (FeNO). RESULTS: The questionnaire had a sensitivity of 0.96 and a specificity of 0.87 for the diagnosis of asthma ever compared to clinical assessment. The overall agreement (kappa) was 0.80. After clinical assessment the prevalence of asthma ever was adjusted from 17.6 % to 16.9 % (95% CI: 15.8-18.0). The most sensitive and specific questions in identifying asthmatic children by the questionnaire were questions asking about diagnosis ('Has the child ever had asthma?') rather than those covering asthma symptoms such as wheeze, shortness of breath and/or cough. A positive exercise test increased the post-test probability for the asthma diagnosis only to a minimal degree. CONCLUSION: Based on the good agreement between the questionnaire responses and the clinical assessments, it is concluded that the questionnaire had good validity and served as a useful epidemiological tool. Detailed clinical testing added little additional information.

Establishing IMMULITE® 2000 cut-off values for serum allergen-specific immunoglobulin and exploring their relationship to exhaled nitric oxide.

AIM: Paediatric cut-off values for serum allergen-specific IgE (sIgE) using the Siemens IMMULITE(®) 2000 system to diagnose allergic rhinoconjunctivitis have not been established. We aimed to determine cut-off levels for sIgE for 10 common inhalant allergens and to study the relationship between sIgE, total IgE and fractional exhaled nitric oxide (FENO ). METHODS: We enrolled 243 schoolchildren, including 164 with allergic rhinoconjunctivitis. Parental interviews, skin prick tests, sIgE, total IgE, FENO measurements, spirometry and exercise tests were performed. RESULTS: Cut-off values with the best combined sensitivity and specificity were above the detection limit of the assay for seven of the ten allergens (0.23-1.1 kU/L). The overall accuracy of the IMMULITE(®) in detecting allergic rhinoconjunctivitis was good. sIgE was superior to total IgE and FENO in predicting allergic rhinoconjunctivitis to timothy, birch, mugwort, cat, dog and house dust mite. FENO was elevated in children with allergic rhinoconjunctivitis, irrespective of asthma. CONCLUSION: Cut-off values for sIgE were dependent on the allergic phenotype and were above the IMMULITE(®) detection limit for seven of ten inhalant allergens. Consequently, using the detection limit for sIgE as the decision point would result in over-diagnosing allergic rhinoconjunctivitis. When measuring elevated FENO in children, allergic rhinoconjunctivitis should be suspected.

Increasing prevalence of asthma, allergic rhinoconjunctivitis and eczema among schoolchildren: three surveys during the period 1985-2008.

AIM: The prevalence of asthma, allergic rhinoconjunctivitis (AR) and eczema among children has increased worldwide in the last four decades, but recent studies disagree as to whether the prevalence is continuing to rise or is levelling off or declining. The aim of this study was to assess time trends in a subarctic population. METHODS: A cross-sectional, questionnaire-based survey was carried out in 2008 among children aged 7-14 years in randomly selected schools in Nordland County, Norway (n = 4150). The results are compared with results from identical studies in 1985 (n = 4870) and 1995 (n = 4456). RESULTS: The main findings were an increasing prevalence of asthma ever (7.3% in 1985 to 17.6% in 2008, p for trend < 0.001) and AR ever (15.9% in 1985 to 24.5% in 2008, p for trend < 0.001), while the prevalence of eczema ever, after an increase between 1985 and 1995, remained unchanged in the last time period. The prevalence of current disease doubled and trebled between 1995 and 2008 for all three diseases. CONCLUSION: A repeated cross-sectional survey between 1985 and 2008 documented an increasing prevalence of asthma ever and AR ever among schoolchildren (7-14 years), together with a considerably increase in current asthma, AR and eczema between 1995 and 2008.

Exhaled nitric oxide decreases during exercise in non-asthmatic children.

INTRODUCTION: Exhaled nitric oxide (FENO) measurements are recommended to be performed before spirometry and exercise challenge tests because forced breathing might influence FENO values. Information on the effect of exercise on FENO is lacking in non-asthmatic children. AIM: To investigate the effect on FENO of a standardized exercise challenge test on a treadmill in non-asthmatic children with and without allergic rhinoconjunctivitis (AR) symptoms. METHODS: From the case-control study 'Asthma and allergy among school children in Nordland', 330 non-asthmatic pupils age 8-16 years were enrolled. FENO was measured at baseline and at 1 min and 30 min after exercise challenge test by the single breath technique with EcoMedics Exhalazer® (Eco Physics, Duernten, Switzerland). RESULTS: Pair-wise comparison of FENO from baseline demonstrated a highly significant reduction in FENO post-exercise for all children at 1 min (27.4%) and at 30 min (16.1%) (P < 0.001). The AR group had a significantly higher decline in FENO value at 1 min post-exercise compared to the non-AR group, 4.2 parts per billion (ppb) vs 2.6 ppb (P < 0.001). Decline in FENO immediately post-exercise was more significant if baseline FENO was ≥ 20 ppb; mean reduction 9.9 (95% CI: 8.7-11.4) ppb. CONCLUSION: FENO is reduced by 27.4% immediately after a standardized treadmill exercise test in non-asthmatic children. Pupils reporting AR symptoms demonstrate a larger decline in FENO value at 1 min post-exercise compared to pupils without AR symptoms. These findings confirm that children should refrain from physical activity before FENO measurement.