['Effect of the pneumatic tube system (PTS) on sample quality is controversial. Herein we aim at evaluating the impact of sample transportation via the PTS on complete blood count (CBC) results.', 'Duplicate CBC samples from normal donors and anemic patients were sent in parallel to the laboratory for testing through the PTS and the courier (CO). We used scatter plots, Bland-Altman plots, correlation coefficient (r), and coefficient of determination for the validation.', 'A total of 115 samples (donors: 59, patients: 56) were tested. There was excellent correlation between both methods for red blood cell parameters (r range\xa0=\xa00.9213-0.9958) and platelet count. White blood cell (WBC) count and differential count showed similar results (r range\xa0=\xa00.8605-0.9821) for all, with exception of basophils which showed modest correlation (r\xa0=\xa00.4827 for patients and 0.5758 for normal donors). Most of the differences in measurement of all CBC parameters were within the 95% confidence interval of the mean difference on Bland-Altman plots.'] Does the pneumatic tube system affect complete blood count results ; a validation study at a tertiary care hospital?