Diagnosing asthma in children: what is the role for methacholine bronchoprovocation testing?

OBJECTIVE: To determine whether measurement of airways responsiveness to methacholine can help physicians diagnose asthma in children. METHODS: Children from the 1995 Manitoba birth cohort were assessed by asthma specialists, had skin testing and measurement of airways responsiveness to methacholine (PC20). We selected children with doctor-diagnosed asthma and healthy children as controls (no asthma, no allergic rhinitis, negative skin tests). Sensitivities and specificities for asthma were calculated. Receiver operating curves were calculated to determine the best fit of the methacholine challenge as a diagnostic test. RESULTS: 640 children were assessed. Two hundred fifteen children with doctor diagnosed asthma and 197 healthy controls successfully completed a methacholine challenge. Airways hyperresponsiveness was a moderately sensitive and specific measure for the diagnosis of asthma in girls, whether atopic (sensitivity of 71% and specificity of 69% at PC20 < or = 4.0 mg/ml) or not (sensitivity of 77% and specificity of 53% at PC20 < or =8.0 mg/ml). Airways hyperresponsiveness was also helpful for the diagnosis of asthma in atopic boys (sensitivity of 67% and specificity of 75% at PC20 < or =2.0 mg/ml), but of absolutely no help in the diagnosis of asthma in nonatopic boys. CONCLUSION: Measurement of airways hyperresponsiveness to methacholine can be useful in children who are atopic and of some value in nonatopic girls. The presence or absence of airways hyperresponsiveness to methacholine is of no help for the diagnosis of asthma in nonatopic boys. Laboratory tests must be placed in context of the clinical assessment of children for asthma.

Should Younger Siblings of Peanut-Allergic Children Be Assessed by an Allergist before Being Fed Peanut?

: The objective of this study was to determine the risk of peanut allergy in siblings of peanut-allergic children. In 2005-2006, 560 households of children born in 1995 in the province of Manitoba, Canada, were surveyed. The index children (8-to 10-year-olds) were assessed by a pediatric allergist and had skin-prick testing and/or capRAST for peanut allergy. Surveys were completed by parents for siblings to determine the presence of peanut allergy. Of 560 surveys, 514 (92%) were completed. Twenty-nine (5.6%) index children were peanut allergic. Fifteen of 900 (1.7%) siblings had peanut allergy. Four of 47 (8.5%) were siblings of peanut-allergic children and 11 of 853 (1.3%) were siblings of non-peanut-allergic children. The risk of peanut allergy was markedly increased in siblings of a peanut-allergic child (odds ratio 6.72, 95% confidence interval 2.04-22.12). Siblings of peanut-allergic children are much more likely to be allergic to peanut. An allergy assessment by a qualified allergist should be routinely recommended before feeding peanut to these children.

Asthma is not enough: continuation of smoking among parents with an asthmatic child.

BACKGROUND: Ideally, on diagnosis of asthma in a child, parents are counselled to decrease environmental tobacco smoke exposure to their children. OBJECTIVE: To determine whether a diagnosis of asthma in children altered parental smoking behaviour toward a reduction in environmental tobacco smoke exposure. METHODS: In 2002/2003, a survey was sent to 12,556 households with children born in 1995 in Manitoba. Parents were asked whether their seven-year-old child had asthma, and whether smokers were present in the home in 1995 and/or currently. The likelihood (OR) of a change in parental smoking behaviour was determined according to the presence of asthma in their child, a family history of asthma, the location of residence (rural or urban) and their socioeconomic status. RESULTS: A total of 3580 surveys (28.5%) were returned. The overall prevalence of parental smoking in 1995 and 2002/2003 was 32.2% and 23.4%, respectively (31.9%/23.2% and 32.3%/23.6% in rural and urban environments, respectively). In 2002/2003, the prevalence of parental smoking in homes with asthmatic children was 29.8%. Parents were not more likely to quit smoking (OR=1.01, 95% CI 0.66 to 1.54) or smoke outside (OR=1.02, 95% CI 0.56 to 1.83) if their child developed asthma. Parental smoking behaviour (quit smoking or smoked outside) did not change if there was a positive family history of asthma (OR=1.04, 95% CI 0.78 to 1.37), if they lived in a rural or urban location (OR=0.94, 95% CI 0.71 to 1.23), or if they were from a low- or high-income household (OR=1.12, 95% CI 0.85 to 1.47). CONCLUSIONS: The likelihood of altering parental smoking behaviour occurred independently of a diagnosis of asthma in their child, a family history of asthma, the location of residence and their socioeconomic status.

The relationship of breast-feeding, overweight, and asthma in preadolescents.

BACKGROUND: Breast-feeding is suggested to be associated with overweight or asthma in children. Overweight and asthma may share common environmental influences of which breast-feeding may be one. OBJECTIVE: We evaluated whether short duration of exclusive breast-feeding and subsequent overweight were associated with asthma. METHODS: A nested case-control study included 246 children with pediatric allergist-diagnosed asthma and 477 controls without asthma at age 8 to 10 years. Information on exclusive breast-feeding was obtained from questionnaire data. Overweight at 8 to 10 years of age was defined as body mass index >/=85th percentile of age and sex-specific growth charts. The association between asthma and exclusive breast-feeding <12 weeks plus overweight, adjusted for sex, parental asthma, aboriginal origin, passive smoking at birth, residence location, and family income, was determined in logistic regression analyses. RESULTS: Exclusive breast-feeding <12 weeks was closely associated with overweight at age 8 to 10 years (P < .001). Exclusive breast-feeding <12 weeks plus overweight was significantly associated with asthma (adjusted OR, 1.81; 95% CI, 1.11-2.95; P = .018). This association appeared to be strong in children whose mothers had asthma (adjusted OR, 3.93; 95% CI, 1.17-13.2) and also in boys (adjusted OR, 2.22; 95% CI, 1.14-4.34). Asthma was not associated with either exclusive breast-feeding <12 weeks or overweight in the absence of the other. CONCLUSION: Short duration of exclusive breast-feeding and subsequent overweight are associated with asthma in susceptible children, suggesting a common pathway. CLINICAL IMPLICATIONS: This finding adds to the importance of promoting prolonged breast-feeding for the prevention of overweight and asthma.

Transient tachypnea of the newborn may be an early clinical manifestation of wheezing symptoms.

OBJECTIVE: To determine risk factors associated with transient tachypnea of the newborn (TTN) and whether TTN is associated with development of wheezing syndromes in early life. STUDY DESIGN: The Population Health Research Data Repository at the Manitoba Centre for Health Policy is a healthcare administrative and prescription database. Data for children diagnosed with a wheezing syndrome (defined as bronchiolitis, acute bronchitis, chronic bronchitis, asthma, or prescription for asthma medication) were obtained. Term children diagnosed with TTN at birth were selected. Cox proportional hazards regression analysis for time to first event of hospitalizations, physician visits, or prescription for an asthma medication up to 7 years of age were calculated. The hazard ratios for wheezing in a child with TTN were compared with healthy newborns. RESULTS: Twelve thousand seven hundred sixty-three children were born at term in 1995 and currently live in the province of Manitoba. Of these children, 308 (2.4%) developed TTN. Maternal asthma, birth weight > or = 4500 g, male sex, and urban location were risk factors for development of TTN. Infants with TTN at birth were at significantly increased risk of a wheezing disorder in childhood (adjusted hazard ratio [HR] = 1.17, 95% CI 1.02-1.34). CONCLUSION: TTN is associated with development of wheezing syndromes in childhood.

The risk of developing food allergy in premature or low-birth-weight children.

BACKGROUND: Premature or low-birth-weight children have increased gut permeability compared with term or normal-birth-weight children. OBJECTIVE: To determine whether premature or low-birth-weight children have an increased risk of developing food allergy compared with term or normal-birth-weight children. METHODS: The 1995 Manitoba Birth Cohort was studied using the Manitoba Health Services Insurance Plan (MHSIP) database. This database is a population-based, health care administrative and prescription database. It has records of every child born and subsequent utilization of the provincial health care system. The diagnosis of food allergy (ICD-9-CM code of 693 in hospital/medical claims or a prescription of injectable epinephrine excluding a sole diagnosis of venom allergy) was obtained up until the year 2002. The relative risks of food allergy in premature or low-birth-weight children compared with term or normal-birth-weight children were determined. RESULTS: A total of 13,980 children were born in 1995 and continue to live in the province of Manitoba. Of these, 592 children (4.23%) were found to have food allergy and epinephrine was prescribed in 316 (2.26%) children. No gestational age or birth weight group had a statistically significant increased risk for food allergy. CONCLUSION: Prematurity and low birth weight are not associated with a change in risk for development of food allergy in childhood. CLINICAL IMPLICATIONS: Immaturity of the gastrointestinal tract or immune response does not seem to change the risk for development of food allergies. We ask whether early exposure to food antigens may protect premature children by increasing immune tolerance to those antigens.