Determination of pathogen IgM antibody and analysis on the value of inflammatory indexes in diagnosing of respiratory tract infection

Objective To explore the application value of the pathogen IgM antibody (IgM-Ab) and inflammatory indicators in the diagnosis of patients with respiratory tract infection (RTI). Methods We prospectively enrolled 1316 pateints with RTI from January to June 2016.Specimens from 557 patients were analyzed and compared the outcome of bacterial cuture and pathogen IgM-Ab detection of patients with bacterial infection (n=50), to those with viral(n=172), mycoplasma(n=112), virus-bacterial mixed infections (n=56), and with those of control group (n=180). Results Respiratory agents were detected in 936 (71.12%) of 1316 patients with RTI.A single agent was identified in 442 patients (47.22%), and multiple agents in 494 (52.78%). Positive bacterial culture results were obtained in 123 specimens (21.32%). Patients with virus-bacterial mixed infections had a significantly higher level of CRP than those with virus infection (Z=-3.070, P<0.05). We established that the mean level of PCT was statistically higher in patients with bacterial infection and those with virus-bacterial mixed infections than that in those with viral patients(Z=-5.512, -4.984, both P<0.05) and in those with mycoplasma infection(Z=-5.174, -5.654, both P<0.05). In patients with bacterial infection and those with virus-bacterial mixed infections, the positive rate of PCT were higher than that in patients with viral(χ2=30.286, 22.695, both P<0.05) and in those with mycoplasma infection (χ2=40.142, 31.156, both P<0.05). The area under receiver operating characteristic (ROC) curve was 0.751 for PCT, lager than that for CRP (P<0.05). Conclusion PCT levels are superior predictors for the diagnosis of bacterial RTI.PCT values combined with IgM-Ab is a fair way to evaluate the etiologic agents at the time of suspicion of RTI. Key words: Respiratory tract infection; C-reactive protein; White blood cells counting; Prealbumin; Procalcitonin