Comparison of gramineae and ragweed pollen counts measured by Hirst's and Cour's traps.

The aim of this study is to appreciate what conclusions may be drawn from the comparison between two different methods for pollen count determination in clinical allergology. In Lyon (France), two pollen collectors are set up in two places separated by ten kilometers, as the crow flies. The Hirst-type trap is on the roof of the Pasteur Institute in the town; the Cour's trap (French Association for Ragweed Study), is located at the meteorological station in the country at the east of the town. In the Rhône-Alpes region, pollinosis is essentially due to Poacae and Ambrosia elatior. The weekly data have been recorded during three years. The results of the two categories of herbaceous plants are not comparable, except as regards the date at which the pollen season commenced. Graminae pollination (GP) commences between 20th April and 6th of May. Ragweed pollination (RP) accurately commences 5th and 6th of August! Differences in the fluctuations of peak concentrations of GP from one trap to the other can be imputed to the collectors, the site where these are located, the method used to process the data, the herbaceous weeds themselves. RPC (the dates of the peaks) are closer and more coherent. Lastly, in allergological practice, the Jacques Dechamp's rule, to only emply with the A.F.E.D.A. trap, is a hardy aid used to predict the week of the all-important peak pollen concentrations of G and R.