[Clinical characteristics of influenza pneumonia in the elderly and relationship between D-dimer and disease severity].

Objective: To clarify the clinical characteristics of influenza pneumonia in the elderly patients and the relationship between D-dimer and the severity of influenza pneumonia.
Methods: In the study, 52 hospitalized patients older than 65 years with confirmed influenza pneumonia diagnosed in Peking University People's Hospital on 5 consecutive influenza seasons from 2014 were retrospectively analyzed. General information, clinical symptoms, laboratory data, treatment methods and prognosis of the patients were collected. The relationship between D-dimer and pneumonia severity was analyzed, and receiver operating characteristic (ROC) curve was used to evaluate the predictive value of D-dimer.
Results: Among the 52 patients, 31 were male (31/52, 59.6%), the average age was (77.1±7.4) years, and 19 of them (36.5%) were diagnosed with severe pneumonia. About 70% patients presenting with fever. In the severe group, the patients were more likely to complain of dyspnea than in the non-severe group (14/19, 73.7% vs . 10/33, 30.3%, P =0.004), severe pneumonia group had higher level of CURB-65 (confusion, urea, respiratory rate, blood pressure, and age>65), pneumonia severity index (PSI), C-reactive protein, urea nitrogen, lactate dehydrogenase, fasting glucose, and D-dimer ( P value was 0.004, < 0.001, < 0.001, 0.003, 0.038, 0.018, and < 0.001, respectively), albumin was lower than that in the non-severe group [(35.8±5.6) g/L vs . (38.9±3.5) g/L, t =-2.348, P =0.018]. There was a significant positive correlation between the D-dimer at the first admission and PSI score ( r =0.540, 95% CI : 0.302 to 0.714, P < 0.001), while a significant negative correlation with PaO ₂ /FiO ₂ ( r =-0.559, 95% CI : -0.726 to -0.330, P < 0.001). Area under the curve of D-dimer was 0.765 (95% CI : 0.627 to 0.872). Area under the curve of PSI was 0.843 (95% CI : 0.716 to 0.929). There was no statistically significant difference in test efficacy between the two ( Z =2.360, P =0.174). D-dimer level over 1 225 μg/L had a positive predict value for influenza pneumonia in hospital death with a sensitivity of 76.92% and a specificity of 74.36%.
Conclusion: Influenza pneumonia in the elderly always has atypical symptoms, dyspnea is a prominent feature in severe cases, D-dimer level is associated with the severity of influenza pneumonia, and greater than 1 200 μg/L has a good predictive value for in-hospital death in the elderly.