COMPARISON OF SYMPTOM SEVERITY IN NATURAL AND EXPERIMENTALLY-INDUCED COLDS

Antiviral and symptomatic therapies for the common cold have been eval uated in studies that use either natural colds in the community or col ds induced by experimental infection with rhinovirus. The purpose of t his study was to compare the severity and natural history of experimen tally induced and naturally occurring colds of undetermined etiology. Forty-one subjects with natural colds were compared to 24 subjects wit h experimental rhinovirus colds. The highest mean daily symptom score, rhinorrhea score, and nasal obstruction score in the natural cold sub jects were 14.2, 2.1, and 2.5 respectively. In contrast, the highest m ean daily symptom score, rhinorrhea score, and nasal obstruction score in the experimental rhinovirus colds were 9.3, 1.8, and 1.8, respecti vely (P < 0.005 compared to natural colds). Similarly, the highest mea n daily mucus weight in the natural colds, 2.9 gms, was significantly higher than in the experimental colds, 2.3 gms (P = 0.01). There was n o significant difference in the lowest mean nasal airflow in the natur al and experimental models, .552 l/sec and .508 l/sec, respectively. T hese results suggest that subjects with natural colds have more severe symptoms than subjects with experimental colds, however, these differ ences may be due to selection bias inherent in the natural cold study design. Both study designs have potential advantages and selection of the most appropriate design is dependent on the specific aims of the s tudy.