Postoperative lymphopenia: An independent risk factor for postoperative pneumonia after lung cancer surgery, results of a case-control study

Objective Postoperative lymphopenia has been proposed as a risk factor for postoperative infections but has never been identified as such in a multivariate analysis. Postoperative pneumonia (POP) is one of the most common complications after lung cancer surgery and is associated with a worse outcome. We aimed to evaluate the association between postoperative lymphopenia and POP after lung cancer surgery. Methods Patients admitted for lung cancer surgery (lobectomy, bilobectomy, or pneumonectomy) aged. 18 years and with no history of an immunosuppressive state were eligible for inclusion. Lymphocyte counts were determined in blood drawn on the day before surgery and at postoperative days 1, 3 and 7. POP diagnosis was based on clinical, biological and radiological data. A logistic regression model adjusted on currently described risk factors for POP was used to explain the onset of this condition. Results Two hundred patients were included, of whom 43 (21.5%) developed POP. Preoperative lymphocyte count was 1.8 +/- 0.6x10(9) cells/L and 2.0 +/- 0.7x10(9) cells/L in patients with and without POP, respectively (P = .091). In both groups, the lymphocyte count nadir occurred at postoperative day 1. In multivariate analysis, lymphopenia at postoperative day 1 was significantly associated with increased risk of POP (odds ratio: 2.63, 95% CI [1.03-5.40]). POP rate at postoperative day 7 was higher in patients presenting low lymphocyte counts (<= 1.19x10(9) cells/L) at postoperative day 1 (P = .003). Conclusions Our study showed that lymphopenia following lung cancer surgery was maximal at postoperative day 1 and was associated with POP.