Comparative study on infection-induced thrombocytopenia among returned travellers

Abstract

Thrombocytopenia is a frequent finding among ill returned travellers and may be caused by a large number of different conditions, including infectious diseases specific or typical for tropical and subtropical regions. In order to assess the diagnostic significance of thrombocytopenia we investigated a large cohort of returned travellers. This was a comparative study in which data collected on 19,473 returned travellers who consulted the outpatient travel clinic of the the University of Munich Hospital between 1999 and 2009 were analysed. Of these, 732 (3.8%) travellers were diagnosed with thrombocytopenia, and their data were compared with those of the remaining 18,741 travellers with normal platelet counts. Thrombocytopenia was significantly more frequent among patients with malaria (63%), acute human immunodeficiency virus infection (48%), dengue fever/dengue haemorrhagic fever (DF/DHF; 47%), Epstein-Barr virus infectious mononucleosis (23%), paratyphoid/typhoid fever (14%), and rickettsiosis (12%). Malaria and DF/DHF caused 25% of all cases of thrombocytopenia (platelet count <140,000/μl) and 75% of all cases of severe thrombocytopenia (platelet count <30,000/μl). Sex, age, country of origin, duration and type of travel were not significantly correlated with thrombocytopenia. The most frequent travel destinations were Asia (42%), Africa (33%), and Latin America (14%). Travellers to Sub-Saharan Africa (high risk for malaria) and to South/South-east Asia (high risk for DF/DHF) had the highest relative risk for thrombocytopenia. Platelet count among returned travellers is an essential screening parameter, as thrombocytopenia is highly correlated with important infectious diseases, particularly with malaria and DF/DHF.