PAFS - POPULATION-ADJUSTED FREQUENCY OF SENSITIZATION .1. INFLUENCE OF SEX AND AGE

Sensitization rates are influenced by sex and age. Crude rates from di fferent departments cannot be compared without taking into account the se variables. However, the influence of sex and age has never been con sidered quantitatively. In 2 hypothetical populations with identical a ge-specific sensitizations rates, but differing age distributions, the influence of age on the overall sensitization rate (crude rate) is de monstrated. Furthermore, by an abstract reflection on rates, the influ ence of the proportions of a population category (e.g., age) on crude rates is shown crude rate=Sigma (category-specific rate x proportion o f population in category)). To account for differing distributions of sex and age, we propose 2 ways. Sex-specific rates should be presented separately. Age-specific rates should be standardized. The standard r ate is defined as: SR=Sigma (category specific ratexproportion of stan dard population in category). Using a standard population with a recta ngular structure (i.e., with equal proportions in each of the category (age) specific groups), the standardized rate is the arithmetic avera ge of the category (age) specific rates. Only for simple routine evalu ations can a standard population with 2 equal groups be used, namely o ver 39 years and under 40 years. The standardized rate can easily be c alculated as SR: (positive rate (%(under 40)+positive rate (%)(over 39 ))/2. The general rule should be to use a ''rectangular'' standard pop ulation with 9 age groups of a 10-year sequence. By using the standard ization procedure, remaining differences found in different department s can no longer be attributed to age and sex. Other factors, such as s election of patients or real epidemiological differences, can then be discussed. The application of population-adjusted frequency of sensiti zation (PAFS) in any publication on prevalences of sensitization is hi ghly recommended. (C) Munksgaard, 1996.