Serum D-dimer changes and prognostic implication in 2009 novel influenza A(H1N1)

Background: The patients with Influenza A (H1N1) have a higher mortality compared with suffering from seasonal influenza. However, many clinical characteristics are still not clear. In the course of clinical treatment on H1N1, we found there were some apparent abnormal clinical indexes being detected at the preliminary diagnosis for severely ill patients, especially the obvious increasing of D-dimer. D-dimer may be associated with the prognosis of Influenza A (H1N1).

Methods: Patients' clinical data (age, gender, body mass index, primary diseases, etc.) and the preliminary diagnostic clinical indexes including blood creatine kinase (CK), creatine kinase isoenzyme (CK-MB), lactic dehydrogenase (LDH), T cell subsets, blood gas analysis, D-dimer, activated partial thromboplastin time (APTT), prothrombin time (PT) and plasma fibrinogen (FG) were retrospectively analyzed.

Results: Compared with the non-respiratory failure group, the cases in respiratory failure group, especially in death sub-group have lower lymphocytes, higher LDH and D-dimer, as well as decreasing oxygenation index during the preliminary diagnosis(P<0.05). The disease severity (Apche II scores) was independently associated with preliminary oxygenation index and LDH (R(2)=0.511, p<0.01). The correlation analysis shows that there is a negative correlation between the D-dimer and oxygenation index (r=-0.510, P<0.01) in the preliminary diagnosis. Meanwhile, there is also a negative correlation between preliminary diagnostic D-dimer and the lowest oxygenation index after admission (r=-0.573, P<0.01).

Conclusions: The peripheral blood lymphocytes (including CD3, CD4 and CD8), LDH, oxygenation index and D-dimer detected in the preliminary diagnosis are important indexes that may affect the disease progress and prognosis of H1N1 patients. The significantly increased D-dimer and corresponding hyoxemia indicate the probability of formation of pulmonary microthrombus. Thus, it may be necessary to consider the anticoagulant therapy.