Twin study of adolescent genetic susceptibility to mosquito bites using ordinal and comparative rating data

Ordinal and comparative rating measures of mosquito attraction and mosquito bite frequency and symptoms were administered in a self-report questionnai re format to a sample of 197 monozygotic and 326 dizygotic Australian adole scent twin pairs at age 12 between 1992 and 1999, in order to investigate t he environmental and possibly genetic determinants of variation between ind ividuals. Repeat measures were obtained from the twin pairs at age 14. Ordi nal variable measures, although providing some support for genetic effects on mosquito susceptibility, were affected by low repeatability. However, an alysis of a comparative rating variable "compared with your twin, who is bi tten by mosquitoes more often?" indicated a strong genetic influence on fre quency of being bitten by mosquitoes, with no significant differences obser ved between males and females. Comparative rating questionnaire items are a potentially valuable tool for complementing and improving the results obta ined from more conventional absolute measures. (C) 2000 Wiley-Liss, Inc.