Background: the role of neutrophil and lymphocyte counts as predictors of prognosis in Community Acquired Pneumonia (CAP) has not been appropriately studied. Methods: this was a retrospective study to evaluate by multivariate regression analysis, the association between neutrophil and lymphocyte counts with mortality at 30-days post discharge in two large cohorts of hospitalized patients with CAP and no prior immunosupression: a multicentric with 1550 patients recruited at 14 hospitals in Spain and a unicentric with 2840 patients recruited at the Hospital Clinic-Barcelona. Findings: The unicentric cohort accounted with a higher proportion of critically ill patients: 586 (20.6%) vs 131 (8.5%) and non survivors 245 (8.6%) vs 74 (4.8%). Lymphopenia (< 1000 lymphocytes/mm3) was present in the 52.8% of the patients in both cohorts. A sub-group of lymphopenic patients, those with lymphocyte counts below decil 3 (677 lymphocytes/mm3 in the multicentric cohort and 651 lymphocytes/mm3 in the unicentric one), showed > 2-fold increase in the risk of mortality, independently of the CURB-65 score, critical illness and receiving an appropriated antibiotic treatment: (OR [CI95%], p) (2.18 [1.21-3.92], 0.009) and (2.33 [1.61-3.33], <0.001) respectively. Neutrophil counts were not associated with mortality risk. Interpretation: Lymphopenia is present in a half of the patients with CAP needing of hospitalization, in absence of antecendents of immunosupression. Lymphopenic CAP with lymphocyte counts < 664 lymphocytes/mm3 constitutes a particular immunological phenotype of the disease which is associated to an increased risk of mortality.

Lymphopenic community acquired pneumonia, an unnoticed phenotype associated to mortality in non immuno-suppressed patients: a retrospective cohort study