title: The clinical usefulness of lymphocyte:monocyte ratios in differentiating influenza from viral non-influenza-like illnesses in hospitalized adults during the 2015 influenza A (H3N2) epidemic: the uniqueness of HPIV-3 mimicking influenza A.
abstract: During influenza epidemics, influenza-like illnesses (ILIs) viruses cocirculate with influenza strains. If positive, rapid influenza diagnostic tests (RIDTs) identify influenza A/B, but false-negative RIDTs require retesting by viral polymerase chain reaction (PCR). Patient volume limits testing during influenza epidemics, and non-specific laboratory findings have been used for presumptive diagnosis pending definitive viral testing. In adults, the most useful laboratory abnormalities in influenza include relative lymphopenia, monocytosis, and thrombocytopenia. Lymphocyte:monocyte (L:M) ratios may be even more useful. L:M ratios <2 have been used as a surrogate marker for influenza, but there are no longitudinal data on L:M ratios in hospitalized adults with viral ILIs. During the 2015 influenza A (H3N2) epidemic at our hospital, we reviewed our experience with L:M ratios in 37 hospitalized adults with non-influenza viral ILIs. In hospitalized adults with non-influenza A ILIs, the L:M ratios were >2 with human metapneumovirus (hMPV), rhinoviruses/enteroviruses (R/E), and respiratory syncytial virus (RSV), but not human parainfluenza virus type 3 (HPIV-3), which had L:M ratios <2. HPIV-3, like influenza, was accompanied by L:M ratios <2, mimicking influenza A (H3N2). In influenza A admitted adults, L:M ratios <2 did not continue for >3 days, whereas with HPIV-3, L:M ratios <2 persisted for >3 days of hospitalization.
authors.affiliation: Infectious Disease Division, Winthrop-University Hospital, 222 Station Plaza North (Suite #432), Mineola, NY, 11501, USA. bacunha@winthrop.org.|School of Medicine, State University of New York, Stony Brook, NY, USA. bacunha@winthrop.org.
authors.forename: B A
authors.initials: BA
authors.lastname: Cunha
authors.affiliation: Infectious Disease Division, Winthrop-University Hospital, 222 Station Plaza North (Suite #432), Mineola, NY, 11501, USA.|School of Medicine, State University of New York, Stony Brook, NY, USA.
authors.forename: J J
authors.initials: JJ
authors.lastname: Connolly
authors.affiliation: Infectious Disease Division, Winthrop-University Hospital, 222 Station Plaza North (Suite #432), Mineola, NY, 11501, USA.|School of Medicine, State University of New York, Stony Brook, NY, USA.
authors.forename: N
authors.initials: N
authors.lastname: Irshad
mesh_terms: D000328:Adult; D003937:Diagnosis, Differential; D058872:Epidemics; D005260:Female; D006760:Hospitalization; D006801:Humans; D007251:Influenza, Human / Q000175:diagnosis* / Q000453:epidemiology* / Q000473:pathology; D007958:Leukocyte Count; D008137:Longitudinal Studies; D008214:Lymphocytes / Q000276:immunology*; D008231:Lymphopenia / Q000175:diagnosis*; D008297:Male; D009000:Monocytes / Q000276:immunology*