The natural history of bronchial hyperresponsiveness

Prognostic factors for the outcome of childhood asthma in adolescence

By the second decade of life asthma symptoms often abate and it may seem that patients with mild asthma have "outgrown" the disease. Unfortunately this is likely to be the exception rather than the rule. Although the severity of asthma symptoms fluctuates with time, the inherited tendency towards respiratory symptoms never disappears and many teenagers who seem to be free of symptoms do, in fact, have persistent asthma. During symptom-free periods subclinical, but nevertheless significant, airways obstruction and/or bronchial hyperresponsiveness may be present. It is not unusual for adults who have been asymptomatic for a number of years to redevelope asthma symptoms. Indeed, much of the so-called adult onset asthma has its roots in childhood. Levison concluded that, in these subjects, it is often not the asthma that is outgrown but the paediatrician. The more severe asthma is in childhood the more likely it is that the disease will persist in adulthood. A complete list of the characteristics of the disease in childhood, and the potential risk factors associated with an unfavourable prognosis, such as pulmonary function and bronchial responsiveness and markers of airway inflammation, is therefore needed. As properly matched and controlled prospective long term studies have not been published it has not been possible to evaluate the effects on prognosis of any single class of antiasthma agent. Such studies are needed to find out if it is possible to alter the natural history of the disease. In theory modern asthma treatments, because they are able to improve symptoms and underlying disease phenomena, are also beneficial in the long term prognosis of childhood asthma. The majority of patients with persistent asthma included in the currently available studies were not receiving adequate treatment. Since compliance with therapeutic regimens in asthma, especially in adolescence, is low, a monitoring system is needed to guarantee adequate follow up and treatment during and beyond puberty.

Asymptomatic bronchial hyperreactivity and the development of asthma and other respiratory tract illnesses in children

BACKGROUND

It is not clear whether asymptomatic bronchial hyperresponsiveness (BHR) in children is a risk factor for the subsequent development of asthma. A longitudinal study was conducted to determine the predictive value of BHR for the development of asthma in a primary care patient population.

METHODS

A standard free running asthma screening test (FRAST) was applied to 956 schoolchildren aged between 4 and 11 years in 1985. Peak expiratory flow (PEF) rates were measured before hard running for six minutes and following a three minute rest period. Children with a fall in PEF of more than 15% were labelled as having a positive FRAST. Clinical data from the patients' notes and from symptom questionnaires were compared with age and sex matched controls for children known to have asthma, and for those with a positive FRAST but no asthma (BHR group). Over the ensuing six years to 1991 further clinical data were gathered to compare the development of asthma and other diseases of the airways in both the BHR groups and their controls.

RESULTS

Of the 956 children exercised in 1985, 60 who were not known to have asthma had an abnormal test. Of the 55 of these studied in 1991, 32 (58%) had developed asthma. The sensitivity of a positive FRAST for the development of asthma was 58%, its specificity 97%, and positive predictive value 72%. Hay fever, eczema, otitis media, "bronchitis," and family history of atopy also occurred more commonly in this group.

CONCLUSIONS

Asymptomatic BHR, as shown by exercise challenge, can predict the development of clinical asthma. This study has also shown a relation between BHR, asthma, and other diseases of the airways, notably upper respiratory tract infection, "bronchitis," and otitis media.

Ketotifen. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic use in asthma and allergic disorders

Ketotifen is an orally active prophylactic agent for the management of bronchial asthma and allergic disorders. Accumulated evidence indicates that after 6 to 12 weeks of administration, ketotifen significantly reduces respiratory symptoms and the need for concomitant antiasthmatic drugs in about 70% and 50%, respectively, of patients with mild to moderate bronchial asthma. However, absolute improvement in lung function is generally slight. Ketotifen also has pronounced antihistaminic and antianaphylactic properties which result in moderate to marked symptom improvement in the majority of patients with atopic dermatitis, seasonal or perennial rhinitis, allergic conjunctivitis, chronic or acute urticaria or food allergy. Comparative trials with established agents--notably sodium cromoglycate (cromolyn sodium) in asthma and histamine H1-antagonists in allergic disorders--indicate that ketotifen has comparable clinical utility. Unlike inhaled sodium cromoglycate, ketotifen ameliorates the symptoms of asthma, rhinitis and dermatitis when present together in atopic patients. Patient acceptance of ketotifen is good, although sedation can be troublesome in older children and adults for the initial 2 weeks of treatment. Weight gain is another notable effect in a small percentage of patients. Thus, ketotifen appears to be a useful agent for the management of allergic disorders and bronchial asthma, particularly in patients for whom oral therapy is preferred. Although a lengthy run-in period is needed in the treatment of asthma, in those patients who respond, continued reduction in the frequency and severity of symptoms and in the use of additional antiasthmatic drugs can be anticipated.