PAFS: population–adjusted frequency of sensitization

Abstract

Sensitization rates are influenced by sex and age. Crude rates from different departments cannot be compared without taking into account these variables. However, the influence of sex and age has never been considered quantitatively. In 2 hypothetical populations with identical age-specific sensitizations rates, but differing age distributions, the influence of age on the overall sensitization rate (crude rate) is demonstrated. Furthermore, by an abstract reflection on rates, the influence of the proportions of a population category (e.g., age) on crude rates is shown (crude rate = sigma (category-specific rate x proportion of 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 rate is defined as: SR = sigma (category specific rate x proportion of standard population in category). Using a standard population with a rectangular structure (i.e., with equal proportions in each of the category (age) specific groups), the standardized rate is the arithmetic average of the category (age) specific rate. Only for simple routine evaluations can a standard population with 2 equal groups be used, namely over 39 years and under 40 years. The standardized rate can easily be calculated as SR: (positive rate (%under 40 + positive rate (%) over 39)/2. The general rule should be to use a "rectangular" standard population with 9 age groups of a 10-year sequence. By using the standardization procedure; remaining differences found in different departments can no longer be attributed to age and sex. Other factors, such as selection of patients or real epidemiological differences, can then be discussed. The application of population-adjusted frequency of sensitization (PAFS) in any publication on prevalences of sensitization is highly recommended.

Contact Sensitivity in Patients with Psoriasis in Vojvodina

“…In order to overcome these differences, sensitization rates to allergens were standardized. Following the recommendations of PAFS (population adjusted frequency of sensitization), the study population was divided into nine separate age groups by decade for age standardization, whereas sex standardization was based on the standard distribution of 40% men and 60% women [4]. …”

“…Apart from 1 irritant reaction to Stellaria media extract 3% pet. (in an AD patient), there was no irritant or delayed reaction suggesting active sensitization produced by other originally made plant extracts [4]. …”

“…Therefore, we performed a prospective study. Sensitization rates to allergens were standardized for age and sex, and rates in women and men were both standardized for age [4]. …”

Epikutantestung mit chemisch modifiziertem Kolophonium

“…In conclusion, patch testing with chemically modified colophony products currently on the mar− ket continues to be helpful. [7]. Die Berechnung von Reak− tions−Index (RI) und Positivity Ratio (PR) erfolgte gemäß den Ori− ginal−Formeln [8,9].…”

The Epidemiology of Fragrance Allergy: Questions and Needs

“…However, being based on floating numerators it does not escape the methodological problems we have already discussed with evaluating the true sensitiaztion rates in the underlying population. The same drawback can be discussed with attempts to standardize by age the sensitization proportions obtained in clinical series, which has been referred to as ‘population-adjusted frequencies’ [15]. By using a standard population with a rectangular structure and nine age groups of 10 years, it has been proposed to calculate the age-adjusted frequency as the arithmetic average of age-specific proportions.…”