Successful triage of suspected hantavirus cardiopulmonary syndrome by peripheral blood smear review: a decade of experience in an endemic region.

Abstract

In 2001, the University of New Mexico Hospitals implemented a rapid screening tool for the triage of suspected hantavirus cardiopulmonary syndrome based on peripheral blood smear morphology. Five criteria guided clinical decisions: thrombocytopenia, hemoconcentration, granulocytic left shift, absence of toxic changes, and more than 10% immunoblasts. Smears meeting four of five criteria were previously shown to have high predictive value for infection. Our retrospective study aimed to determine clinical performance of this test over the past decade. Computerized records of 188 smear results were compared with serology. Receiver operator characteristic curve analysis confirmed that the four of five cutoff was the most clinically useful, with sensitivity and specificity of 89% and 93%, respectively. All patients meeting five of five criteria had confirmed infections. Fifteen discordant results were uncovered, explained by positive subsequent tests in the same patient or severe disease without further testing. Our findings confirm that peripheral smear analysis is clinically useful in this endemic region.