Longitudinal case analysis in atopic dermatitis

The current knowledge on atopic dermatitis comes mainly from cross-sectiona l studies, which are not suited to establish time-courses or causal links i n complex diseases. As an alternative approach, the method of longitudinal case analysis by the auto-regressive integrated moving average (ARIMA) meth od has been introduced to investigate the pathogenesis of atopic dermatitis . The method was applied to the investigation of 2 patients suffering from severe and moderate atopic dermatitis, Disease activity, peripheral blood p arameters (differential blood count, lymphocyte subpopulations, immunoglobu lin E, eosinophilic cationic protein, soluble interleukin-2 receptor), ment al stress and environmental factors were determined daily for 50 days. Both patients showed a positive correlation between CD4(+) and CD25(+) T-cells, a negative correlation between CD16/56(+) natural killer cells and CD4(+) T-cells, a negative correlation between eosinophils and polymorphonuclear l eukocytes, and a time-shifted positive correlation of up to 2 days between scores quantifying mental stress and disease activity. A positive correlati on between T-cells and polymorphonuclear leukocytes, CD4(+) T-cells and the CD45RA(+) subtype, as well as a negative correlation between stress and eo sinophils, sports and eosinophils, and sports and disease activity were fou nd only in one patient with more severe atopic dermatitis. In conclusion, l ongitudinal time-series analysis might represent an interesting and adequat e method to generate and test new hypotheses on biomedical problems which c annot be addressed by cross-sectional studies.