Cellular response to influenza infection:Lymphopenia and a reduced lymphocyte/monocyte ratio

Objectives: Provisional work has proposed a diagnostic role investigating cellular responses in acute viral respiratory pathology. Analysing patients with influenza(flu), objectives were(1)to assess magnitude of lymphocyte and monocyte responses in acute infection and(2)report on the potential benefit if detecting lymphopenia and a reduced lymphocyte to monocyte ratio(LMR) Methods: Retrospective analysis of all adults with flu admitted to this trust during winter season 2016/7. Computer records provided differential white cell counts as relative(%of total white cell counts, WCC)and absolute counts for lymphocytes(normal range 1-4x109)and monocytes(0.1-0.9x109);analysis was with SPSS Results: 143(54% female)adults(142 Flu A [H3N2]and 1 Flu B)were admitted. Mean age was 70.3(SD 19.4, range 20-98)years. Flu was primary diagnosis for 53(37%);43/90(48%) remaining also had a respiratory presentation. Lymphocyte count<20% WCC presented in 122(85%)and monocyte count >10%WCC in 43 (30%)with both markers in 35(25%). Lymphocyte counts were skewed, median 0.8(IQ 0.5-1.2)with lymphopenia at initial testing in 87(60%);among others there was a fall from admission values in 45 (31%). The lymphocyte/monocyte ratio (LMR) was <2 in 115(80%)of all presentations and specifically in 82/87(94%)with initial lymphopenia Conclusions: Irrespective of whether primarily with flu or as a concurrent illness, acute lymphopenia and a LMR<2 at presentation as a measure of cellular response in admitted patients potentially presents an early and alternative strategy identifying patients with acute flu. Future work is required to establish sensitivity, specificity, negative and positive predictive values in a wider unselected similar population