Characterisation of swabbing for virological analysis in the Spanish Influenza Sentinel Surveillance System during four influenza seasons in the period 2002-2006

This study sought to characterise the swabbing pattern in the Spanish Influenza Sentinel Surveillance System (SISSS) and ascertain to what extent the system meets the guidelines currently being drafted by The European Influenza Surveillance Scheme (EISS). Data on seasons 2002/2003 to 2005/2006 were drawn from SISSS. The study analysed collection and dispatch of swab specimens for virological analysis by reference to variables relating to patient sex, age group, vaccination status, specimen collection period, period of influenza activity, time of swabbing and epidemiological season. SISSS adapts to EISS recommendations with respect to the specimen collection period and period of influenza activity, but there is a tendency to collect fewer specimens than recommended as the age of patients increases, and in the case of elderly patients (65 years and older), frequency of collection is clearly insufficient. Furthermore, sentinel physicians collect a higher percentage of specimens in cases where patients have received the influenza vaccine.