PT - JOURNAL ARTICLE AU - Fergus W Hamilton AU - Rupert Payne AU - David T Arnold TI - Prior lymphopenia is associated with mortality in primary care pneumonia: a cohort study AID - 10.3399/bjgp20X713981 DP - 2020 Nov 24 TA - British Journal of General Practice PG - bjgp20X713981 4099 - http://bjgp.org/content/early/2020/11/29/bjgp20X713981.short 4100 - http://bjgp.org/content/early/2020/11/29/bjgp20X713981.full AB - Abstract Background: Lymphopenia (reduced lymphocyte count) during infections such as pneumonia is common and is associated with increased mortality. Little is known about the relationship between lymphocyte count prior to developing infections and mortality risk. Aim: To identify whether patients with lymphopenia who develop pneumonia have increased risk of death. Design and Setting: A cohort study in the Clinical Practice Research Datalink (CPRD), linked to national death records. This database is representative of the UK population, and is extracted from routine records. Methods: Patients aged >50 years with a pneumonia diagnosis were included. We measured the relationship between lymphocyte count and mortality, using a time-to-event (multivariable Cox regression) approach, adjusted for age, sex, social factors, and potential causes of lymphopenia. Our primary analysis used the most recent test prior to pneumonia. The primary outcome was 28 day, all-cause mortality. Results: 40,909 participants with pneumonia were included from 1998 until 2019, with 28,556 having had a lymphocyte test prior to pneumonia (median time between test and diagnosis 677 days). When lymphocyte count was categorised (0-1×109/L, 1-2×109/L, 2-3×109/L, >3×109/L, never tested), both 28-day and one-year mortality varied significantly: 14%, 9.2%, 6.5%, 6.1% and 25% respectively for 28-day mortality, and 41%, 29%, 22%, 20% and 52% for one-year mortality. In multivariable Cox regression, lower lymphocyte count was consistently associated with increased hazard of death. Conclusion: Lymphopenia is an independent predictor of mortality in primary care pneumonia. Even low-normal lymphopenia (1-2×109/L) is associated with an increase in short- and long-term mortality compared with higher counts.