Choosing the right outcomes

Outcome measures are used to monitor the effects of interventions in clinic al practice or in formal clinical trials. They may also be used to assess c hanges within populations either spontaneously or as a result of public-hea lth measures. They are used to monitor the course of illness as part of a m anagement plan or, for larger groups, to identify changes brought about, fo r instance, by migration or immunization. The choice of outcome measure dep ends on the age of the child, the complexity of the outcome (for instance, whether its application is to individuals or populations), and the time sca le over which it is necessary to detect changes in outcome. The most common ly used outcome measures are clinical symptoms, which are often compiled in to scoring systems. Surprisingly, these are often the least well-validated measures of outcome. Physiologic measures, although well validated, are dif ficult to apply to infants and pre-school children. The role of inflammator y markers is currently limited to research rather than clinical practice. O ther outcome measures such as quality of life, impact-of-asthma instruments , and measures to determine the health-economic aspects of asthma are poorl y developed in childhood. The right outcome depends on the question being a sked, the age of the subjects, and the time scale and complexity over which measurement is required.