Etiologic diagnoses of lower respiratory tract infections (LRTI) have been relying primarily on bacterial cultures that often fail to return useful results in time. Although DNA-based assays are more sensitive than bacterial cultures in detecting pathogens, the molecular results are often inconsistent and challenged by doubts on false positives, such as those due to system- and environment-derived contaminations. Here we report a nationwide cohort study on 2986 suspected LRTI patients across P. R. China. We compared the performance of a DNA-based assay qLAMP (quantitative Loop-mediated isothermal AMPlification) with that of standard bacterial cultures in detecting a panel of eight common respiratory bacterial pathogens from sputum samples. Our qLAMP assay detects the panel of pathogens in 1047(69.28%) patients from 1533 qualified patients at the end. We found that the bacterial titer quantified based on qLAMP is a predictor of probability that the bacterium in the sample can be detected in culture assay. The relatedness of the two assays fits a logistic regression curve. We used a piecewise linear function to define breakpoints where latent pathogen abruptly change its competitive relationship with others in the panel. These breakpoints, where pathogens start to propagate abnormally, are used as cutoffs to eliminate the influence of contaminations from normal flora. With help of the cutoffs derived from statistical analysis, we are able to identify causative pathogens in 750 (48.92%) patients from qualified patients. In conclusion, qLAMP is a reliable method in quantifying bacterial titer. Despite the fact that there are always latent bacteria contaminated in sputum samples, we can identify causative pathogens based on cutoffs derived from statistical analysis of competitive relationship. Trial Registration ClinicalTrials.gov NCT00567827
Objective To compare the difference of clinical and radiological findings between patients with nonspecific interstitial pneumonia(NSIP),cryptogenic organizing pneumonia(COP),and desquamative interstitial pneumonia(DIP).Methods Case history and high-resolution computed tomography(HRCT),pathological findings of 8 patients with diagnoses of NSIP,COP and DIP hospitalized in the hospital were reviewed.Results The mean age at onset was 54.5 years,and there were more female patients(5 patients).Expectoration(8 patients),cough(7 patients) and dyspnea(7patients) were most common symptoms.Velcro-type crackles were more common in patients with NSIP.The dominant CT pattern exhibited in NSIP patients was ground-glass attenuation with a random,subpleural distribution.The most typically findings in the patients with COP was consolidation with or without ground-glass attenuation with bronchovascular distribution.And in the patients with DIP,subpleural ground-glass attenuation was dominant change.Conclusion There is no significant difference of symptoms and physical signs among the groups,but HRCT has some characteristic findings in accordance with the pathological changes.
Objective To investigate the value of serum procalcitonin (PCT) in diagnosing lower respiratory tract infection (LRTI) in adult.Methods In a retrospective study,97 patients were enrolled,who admitted into Peking University People's Hospital with suspected LRTI from July to December 2008.During analysis,the subjects are categorized into groups of LRTI with sepsis,hospital-acquired pneumonia(HAP),community-acquired pneumonia(CAP),acute exacerbation of chronic obstructive lung disease (AECOPD),other LRTI and non-infectious diseases.In these cases,the following parameters were assessed regularly,such as white blood cell count,erythrocyte sedimentation rate( ESR),C-reactive protein (CRP),PCT,bacterial culture of both sputum and blood,and Acute Physiology and Chronic Health Evaluation (APACHE) Ⅱ score.PCT levels were determined using antibody-coated tubes as a complete diagnostic-kit (LUMI test Pro-Calcitonin) in a Luminometer.Results Mean PCT levels in groups of LRTI with sepsis, hospital-acquired pneumonia ( HAP ), community-acquired pneumonia ( CAP ), acute exacerbation of chronic obstructive lung disease( AECOPD),other LRTI,non-infectious diseases were 10.1 (0.7 -37.0),0.3(0.1 -0.8),0.2(0.1 -0.9),0.2(0.1 -0.4),0.3(0.1 -0.5),0.1 (0.1 -0.2) mg/L,respectively.There were statistical differences between these groups (H =19.898,P ＜ 0.01 ).And the PCT levels in groups of LRTI with sepsis,HAP,CAP,AECOPD,other LRTI were higher than group of non-infectious diseases ( U values were 0,18.000,81.000,20.000,all P ＜ 0.01 ).Patients with sepsis exhibited strongly higher PCT levels than patients with other lung diseases ( U values were 11.000,45.000,3.000,4.500,all P ＜ 0.01 ).Pearson correlation analysis of PCT levels with positive bacterial cultures and APACHE Ⅱ score was performed ( r =0.449).ROC analysis revealed that optimal discrimination between LRTI and non-infectious diseases could be performed at the cut-off point of 0.5 mg/L with a sensitivity of 32.6％ and specificity of 100％,while at a suggested cut-off point of 0.235 mg/L with a sensitivity of 53.9％ and specificity of 100％.Conclusions PCT is a more useful parameter for diagnosing lower respiratory tract infections( especially for those with sepsis) than other infectious markers such as CRP,ESR and white blood cell count.The sensitivity of PCT could be elevated with a reduction of the cut-off level.
Key words:
Respiratory tract infections ; Calcitonin; Protein precursors
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