[The life span of red blood cell in patients with severe/very severe aplastic anemia].

Objective: To explore the life span of red blood cells (RBC) in patients with severe/very severe aplastic anemia (SAA/VSAA).
Methods: Clinical data of 128 SAA/VSAA patients from November 2016 to April 2017 were retrospectively analyzed, and 13 healthy volunteers in the same period was used as normal control. The endogenous Breath Carbon Monoxide (CO) test was used to detect the life span of RBC in SAA/VSAA patients, and the effect of immunosuppressive therapy (IST) on the life span of RBC in these patients was explored.
Results: The mean life span of RBC in 51 untreated SAA/VSAA patients was (50.69±21.43) d, which was significantly shorter than that in normal controls[(111.85±31.55) d](t=-6.611, P<0.001). The mean life span of RBC in 77 patients treated with IST was (87.14±39.28) d. The mean life span of RBC in complete responses (CR), hematologic response (HR) and non-response (NR) patients were (106.15±32.12) d, (92.00±38.60) d and (50.44±21.56) d, respectively. The life span of RBC in patients with HR was significantly longer than that in newly diagnosed and NR patients (t=7.430, P<0.001; t=4.846, P=0.002), which was similar to that in the normal controls (t=-1.743,P=0.085). There was no statistical significance between CR patients and the normal controls in the mean life span of RBC (t=-0.558, P=0.579). No factor affecting the RBC life span was found in univariate logistical regression analyses in the newly diagnosed SAA/VSAA patients. The serum levels of IL-2R and IL-6 were much lower in HR patients than NR patients[IL-2R: 4.3×105 U/L vs 6.5×105 U/L, z=-2.733, P=0.006; IL-6: 2.6 (2.0-17.7) ng/L vs 6.1 (2.0-14.4) ng/L, z=-2.968, P=0.003]. Of the 51 newly diagnosed patients, 38 received IST and their 3-month curative effect was evaluated. Receiver operator characteristics (ROC) curve was used to analyze the predictive effect of RBC life span of untreated patients on the efficacy of IST before treatment. The cut-off point was 60 days with sensitivity of 37.5% and specificity of 86.4%. In 9 cases with life span of RBC>60 d before IST, 6 cases acquired HR, while in 29 cases with life span of RBC ≤ 60 d before IST, 10 cases acquired HR, the difference was not statistically significant (P=0.128).
Conclusion: The life span of RBC in SAA/VSAA patients was shortened, which can be improved even recovered to the normal after IST. Elevated cytokines might play a role in the pathophysiology of the shortened RBC life span in SAA/VSAA.