Prevalence and reliability of asthma symptoms in primary school children in Cape Town

BACKGROUND

Childhood asthma is believed to be a serious problem in Cape Town, South Africa. This study aimed to measure the prevalence and reliability of asthma symptoms and reported asthma in Cape Town schoolchildren aged mainly 7 and 8 years, and to assess underdiagnosis.

METHOD

A questionnaire was completed by parents of 1955 children, followed by 620 personal interviews repeating the questions.

RESULTS

The prevalence of recent wheeze (previous 12 months) (26.8%) was high by international comparison, but not that of reported asthma (10.8%). Among children with more than 12 recent attacks of wheeze, only 60% were reported as asthmatic and 55% as receiving regular treatment. Symptom prevalences varied with the respondent's familial relationship to the child. On some questions the interview produced higher wheeze prevalences than the self-administered questionnaire. Repeatability of questions varied: asthma over (kappa = 0.69), recent wheeze (kappa = 0.59), and recent sleep disturbance by wheeze (kappa = 0.56) were the most reliable.

CONCLUSIONS

Prevalence based on symptom reports may vary with the respondent and between self- and interviewer-administered questionnaires. Also, certain questions currently proposed for childhood asthma questionnaires may be unreliable. Nevertheless, it can be concluded that the prevalence of wheeze is high in this population, and that underdiagnosis and undertreatment of asthma are a problem.

Accumulation of house-dust mite (Der-p-1) levels on mattress covers

Mattresses serve as a large reservoir for house-dust mite antigens and harbour the highest mite levels within the household. Mite reduction measures have previously been shown to be unsuccessful. The effect of mattress covers and acaracides on Der-p-1 levels in the mattresses of 60 patients with mite-allergic asthma was studied. Der-p-1 levels were measured using monoclonal antibodies (ELISA method). Baseline levels were recorded and re-assessed at 8-week intervals over a 6-month period. Patients were randomised into three equal groups. In group A mattresses were treated with Metsan (Snowchem) and benzylbenzoate only; group C had their mattresses covered with mattress covers (Allergy Control Products). Group B was the control group. We were unable to demonstrate any reduction of mite levels in the beds of all 3 groups. In fact all 3 groups demonstrated an increase in Der-p-1 levels over the study period, viz. group A (mean pre: 14.28, post: 34.18 micrograms/g dust); group C (mean pre: 8.26, post: 20.80 micrograms/g dust) and group B (mean pre: 18.21, post 38.47 micrograms/g dust). However, 12 patients in group C had their mattress covers washed in hot water at weekly intervals over a 5-week period at the end of the study. The results demonstrated a significant reduction in mite levels (mean pre: 41.95, post: 26.2 micrograms/g dust; P = 0.027). We therefore conclude that the use of mattress covers per se does not reduce Der-p-1 levels. The regular application of benzylbenzoate and Metsan does not prevent the accumulation of Der-p-1 on mattresses either.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of a single treatment of an acaricide, Acarosan, and a detergent, Metsan, on Der p 1 allergen levels in the carpets and mattresses of asthmatic children

Baseline levels of the house-dust mite allergen, Der p 1, were measured on the carpets and mattresses of 60 pure-mite-sensitive asthmatic children in the Cape Peninsula, by means of an enzyme-linked immunosorbent assay (ELISA). High levels of mite allergens were recorded (range 2-50 micrograms Der p 1/g dust). In order to investigate the efficacy of the application of acaricides to carpets and bedding, 3 groups of 20 children were studied. Carpets and mattresses in group A were treated with a detergent, Metsan (Snowchem), and in group B with Metsan combined with the acaricide, Acarosan (Noristan). Group C was a control group in which no treatment was applied. The level of airway hyperreactivity (PC20) to histamine was measured at the beginning of the study and again 3 months after acaricide treatment. Significant reductions in carpet Der p 1 levels were achieved in group A (22.83 v. 13.26 micrograms Der p 1/g dust; P = 0.04) and group B (21.76 v. 13.26 micrograms Der p 1/g dust; P = 0.01), but mite levels were not reduced in any of the mattresses treated. There was also no improvement in airway hyperreactivity in any of the groups. This study clearly demonstrates that at present it is not possible to reduce Der p 1 antigen levels in mattresses in the Cape Peninsula with the available acaricides, even when one of these is combined with a detergent solution. Until strategies are developed which will significantly reduce Der p 1 levels in the bedding of sensitive individuals, a reduction in ongoing airway inflammation and airway hyperreactivity cannot be expected.

Increase in hospital admissions for acute childhood asthma in Cape Town, 1978-1990

To determine whether hospital admissions for acute childhood asthma were rising in Cape Town in line with the experience of other countries, Red Cross War Memorial Children's Hospital's records for the period 1978-1990 were analysed. These were compared with total admissions for non-surgical causes and lower respiratory tract illness as well as those for bronchiolitis and pneumonia. Asthma admissions showed a sharp upward trend from 1978 to 1984, a slower rise through 1987 and a levelling off since. The profile of hospital admissions for respiratory illness was also analysed. Black children were under-represented among asthma admissions compared with those for pneumonia. Asthma admissions occurred throughout the year but showed seasonal peaks in May and November. Reasons for these trends and patterns are discussed, as well as hypotheses for further research into the epidemiology of asthma in South Africa.

Comparison between the Acarex R test and a Der p 1 ELISA for the detection of house-dust mites in the homes of asthma sufferers

Exposure to house-dust mite allergens in early childhood is an important determinant of the subsequent development of asthma. The Acarex R semi-quantitative test (Noristan) is marketed for use in patients' homes to assess mite levels in house dust. In order to evaluate the reliability of the test in a coastal area where house-dust mites are known to be prevalent, house-dust mite levels were estimated in 119 dust samples obtained from the homes of asthmatic children in a comparative study, by means of the Acarex R test and a Der p 1 enzyme-linked immunosorbent assay (ELISA). A linear regression of the 4 Acarex classes against log Der p 1 revealed a significant correlation (P = 0,0001) but there was a poor correlation between low Acarex R scores and the Der p 1 allergen levels determined by ELISA. Acarex R scores of 2 and 3 were usually associated with Der p 1 levels greater than 10 micrograms/g dust. Our studies indicate that the Acarex R test will identify high levels of mite allergens. Although its application may be limited in coastal areas such as the Cape Peninsula, it may be more useful inland, in climates where house-dust mites are not commonly encountered in all homes.

A placebo controlled trial of fluticasone propionate in asthmatic children

Fluticasone propionate is a synthetic steroid for use by the inhaled route. It's high topical potency and low systemic bioavailability make it suitable for use in asthmatic children. A total of 258 children were randomised in a double-blind study to receive fluticasone propionate (50 micrograms bd) as the dry powder formulation inhaled via a Diskhaler inhaler, or matched placebo (with current therapy) for 4 weeks throughout which time diary cards were completed. During clinic visits lung function and adrenal function were measured. Fluticasone propionate produced a significantly greater increase in morning peak expiratory flow rate (PEFR) (adjusted mean difference over days 1-28, 17 l/min (95% CI; 10, 24); P < 0.001) and evening PEFR (adjusted mean difference over days 1-28, 16 l/min (95% CI; 9, 23); P < 0.001). In addition, diary card symptom scores, beta 2-agonist rescue and clinic lung function improved significantly on fluticasone propionate. There were few adverse events and basal plasma cortisol remained within the normal range. In conclusion fluticasone propionate at 50 micrograms bd is superior to placebo (current therapy) in the treatment of childhood asthma with no evidence of adverse effects.

Seasonal and recurrent intensive care unit admissions for acute severe asthma in children

Life-threatening attacks of asthma requiring intensive care unit (ICU) management at Red Cross War Memorial Children's Hospital in Cape Town were noted to occur in some patients in the same or adjacent months of different years. A retrospective case-controlled study was performed of 21 such 'seasonal' patients who presented to the ICU over a 14-year period. The group made up 6.5% of all asthma patients admitted to the ICU and their 65 admissions made up 15.6% of all ICU asthma admissions during this period. The control group consisted of patients with recurrent admissions that occurred in 'random' months. The two groups were compared in respect of demographic and clinical data. Patients requiring seasonal admissions were shown to form a distinct sub-population of children with severe asthma, some with a family history of fatal asthma, who were less likely to 'outgrow' asthma in childhood, were more likely to require maintenance steroid therapy for asthma management, and significantly more often had positive radioallergosorbent tests to Aspergillus and Cladosporium sp. and to grass pollen. A retrospective analysis of dates of severe asthma attacks may identify individual seasonality, which is a risk factor for life-threatening and intractable asthma.

Hydration in severe acute asthma

Twenty children were studied during severe attacks of acute asthma to find out how dehydrated they were on admission to hospital. Mean body weight on admission was 97.8% of their reference stable weight seven to 10 days after the attack and in only three children was it less than 95% of the stable weight. Bedside assessment of dehydration was unreliable. The mean packed cell volume was significantly higher on admission than 7-10 days later (0.44 compared with 0.42, difference 0.02 SE 0.01). Serum sodium and potassium concentrations and osmolality on admission were within normal ranges. The degree of dehydration correlated best with a fall in blood pH. There was no association between the degree of dehydration and the recovery of the peak expiratory flow rate during the first 24 hours or thereafter. We conclude that mild dehydration is common in severe acute childhood asthma. Fluid given at a rate of 50 ml/kg/24 hours was safe and appropriate for these children.

Genetic and environmental influences on cord blood serum IgE and on atopic sensitisation in infancy

It has recently been reported that cord blood serum IgE (CBsIgE) concentrations in a black Third-World cohort were significantly higher than those in a similar cohort of white and coloured newborns, and were not influenced by an atopic family history (aFH). This study reports on the 1-year follow-up of these newborns carried out to determine whether statistical differences in median CBsIgE values at birth could be found between infants in each ethnic group who subsequently developed clinical atopy in the first year of life and those who remained healthy. The infants were seen at 3, 7 and 12 months of age. At each visit a detailed history was taken from the mothers, the infants were examined clinically for the presence of atopic disease and blood was taken for immunological assay (total serum IgE by paper-disc radio-immunosorbent testing, and radio-allergosorbent testing for egg-white, cow's milk and Dermatophygoides pteronyssinus). A combination of clinical and immunological variables was assessed in order to categorise the infants into 'atopic' or 'not atopic' groups at the end of the 1-year follow-up period. The black infants who completed the study had the lowest incidence of aFH (16%), but 64% of them developed atopic disease during infancy. The median CBsIgE values for the black infants who became atopic were lower than, but not statistically different from, those for the group who remained non-atopic (P = 0.57). The white and coloured infants who completed the study had 81.6% and 30.4% incidences of aFH respectively, with 47.4% and 58.7% respectively developing atopic disease during infancy.(ABSTRACT TRUNCATED AT 250 WORDS)

A multi-allergen screening test for suspected allergic disease in coloured children

The measurement of total serum IgE levels is widely used as a screening test for allergic disease but lacks specificity in South African subjects because of the presence of ethnic and environmental factors, e.g. parasite infestation, which also raise total serum IgE. The reliability of a new in vitro multi-allergen test, Phadiatop (Pharmacia), which is not influenced by parasitic infestation, was investigated as a screen for allergic disease in coloured children. Phadiatop assays and total serum IgE levels performed on 18 children with known allergic disease were compared with 21 non-allergic individuals. All the allergic, but only 2 of the non-allergic children had a positive Phadiatop result (P = less than 0.01; chi-square test) but there was no significant difference between the number of allergic or non-allergic children with elevated total serum IgE levels (P = greater than 0.1). The Phadiatop test demonstrated a specificity of 90% compared with 28% for total serum IgE. The predictive value of a negative Phadiatop result was 90% compared with 54% for total serum IgE levels. These data indicate that the Phadiatop test is a more specific screening test for allergic disease than total serum IgE levels in coloured children.

The influence of ethnicity, an atopic family history, and maternal ascariasis on cord blood serum IgE concentrations

Raised concentrations of cord blood serum (CBs) IgE have previously been demonstrated to reflect a hereditary predisposition for atopy in First World, predominantly white populations. A cross-sectional study of 53 black, 52 white, and 58 mixed race newborn infants and maternal pairs was performed in a multiethnic, mixed First and Third World society. The CBs IgE concentrations were measured with a modification of the standard IgE PRIST, which could reliably determine IgE concentrations to an accuracy of 0.01 kU/L. The black group had the highest geometric mean and median CBs IgE concentrations (0.21; 0.16 kU/L), followed by the white group (0.12; 0.12 kU/L) and the mixed group (0.10; 0.08 kU/L). If those newborn infants with an atopic family history and maternal ascariasis were excluded, the remainder had geometric mean and median CBs IgE concentrations of 0.20; 0.16 kU/L in the black subgroup, followed by values of 0.06; 0.05 kU/L in the mixed subgroup, and 0.05; 0.07 kU/L in the white subgroup. Statistically significant ethnic differences in the median CBs IgE concentrations of these subgroups were demonstrated between the black-white (p less than 0.05) and the black-mixed (p less than 0.005) ethnic groups. A positive family history of atopy influenced the CBs IgE concentrations in the white and mixed groups but not in the black group. Of those newborn infants with a CBs IgE concentration greater than 0.5 kU/L, a family history of atopy was found in 100% of the white newborn infants, in 58.3% of the mixed newborn infants, and only in 14.3% of the black newborn infants. Many of the black newborn infants without a family history of atopy had extremely high CBs IgE concentrations. The influence of maternal ascariasis was equivocal in the mixed group but of no significance in the black group. The high CBs IgE concentrations in the black newborn infants, independent of an atopic family history and maternal ascariasis, suggest that this atopic marker may therefore be of limited use in identifying the "high allergic-risk" newborn infant in black Third World populations who appear to represent a pool of genetic high IgE-responder phenotypes.

Anti-Staphylococcus aureus-specific IgE in atopic dermatitis

Serum samples from 60 adults and 64 children with atopic dermatitis were tested for antistaphylococcal IgE antibodies with RAST discs coupled to cellular proteins from Wood 46 strain S. aureus. Anti-S. aureus IgE antibodies were detected in 19 (29.6%) of the children and 14 (23.3%) of the adult patients. Anti-S. aureus IgE-positive adults had more severe and prolonged disease than those who were negative. Two groups of children comprising 10 who were anti-S. aureus IgE positive and 10 who were negative were compared. Children with anti-S. aureus IgE antibodies had more severe and more extensive disease (p less than 0.05), a greater prevalence of cutaneous S. aureus infections (p less than 0.05), higher mean total serum IgE level (p less than 0.05), a greater prevalence of specific IgE responses to food allergens (p less than 0.05), and a higher percentage of helper T cells (p less than 0.05) than children who were negative for these antibodies.

The effects of soft-drink preservatives on asthmatic children

Sulphites, used extensively as preservatives in foods and soft drinks, are known to precipitate asthma attacks in 5-10% of susceptible children. Among children attending the Allergy Clinic at the Red Cross War Memorial Children's Hospital, Cape Town, many were found to be sensitive to sulphites. The basis of asthma therapy is modification of the environment and avoidance of precipitating factors. Medical personnel counselling parents of asthmatic children should be aware of this factor. A list of soft drinks containing sulphites and other preservatives is included.

Is Mycoplasma pneumoniae a precipitating factor in acute severe asthma in children?

A randomized prospective trial in 39 children with acute severe asthma admitted to the emergency ward of the Red Cross War Memorial Children's Hospital and a matched comparative group showed that Mycoplasma pneumoniae was not a precipitating factor.

Bee venom allergy

Bee venom allergy is a common problem in medical practice. The immunological mechanisms and management thereof are reviewed.

Sodium cromoglycate in asthma therapy. A retrospective survey

The data obtained in a retrospective survey of the use and effectiveness of sodium cromoglycate (Lomudal; Fisons) therapy in 635 children and young adults support the findings of other long-term studies that this drug is effective and safe in the treatment of children and young adults with clear evidence of allergy contributing towards their asthma. Its administration by Spinhaler can be commenced successfully at 4 years of age or even younger and continued for as long as is required. The drug is worth a therapeutic trial in any patient with asthma requiring regular medication to control symptoms. The absence of demonstrable allergy does not entirely preclude a favourable response. Once a patient's asthma has been stabilized, sodium cromoglycate enables concomitant therapy (especially with beta 2-adrenergic stimulants and corticosteroids) to be reduced.

The effect of terbutaline sulphate on exercise-induced asthma in children

Terbutaline sulphate (Bricanyl; Keatings) aerosol or placebo aerosol was administered in a randomized fashion to 26 asthmatic children with proven exercise-induced asthma. The children were then subjected to the modified standard exercise challenge test involving running on the level for 6 minutes. Terbutaline sulphate aerosol had a marked protective effect against exercise-induced asthma in these children. Compared with placebo, a significant reduction in exercise-induced bronchospasm was achieved. The improved design of the mouthpiece, incorporating a newly introduced 'misting tube' enabled the children to handle the apparatus easily. The need to synchronize the activation of the aerosol with inhalation was eliminated. Terbutaline aerosol can be recommended to protect children affected by exercise-induced asthma. The preparation can be given prior to the exercise challenge and will offer prolonged and adequate protection against exercise asthma.

'Honking': Psychogenic cough tic in children

Psychogenic cough tic is a troublesome complaint. The cough is a noisy bark or honking, repeated frequently while the child is awake, but absent during sleep. Clinical and laboratory findings are negative, and cough suppressants and other medications are ineffective. The cough usually starts in the winter months and may be preceded by an upper respiratory tract infection. School phobia is frequently a contributory cause, but other psychological problems must also be considered. Treatment is usually by suggestion and identification of the underlying psychological problem. In some cases tranquillizers may be required.