Role Of Loop-Mediated Isothermal Amplification Inpathogens Diagnosis Of Severe Community-Acquired Pneumonia In Clinical Setting

Background:There was lower positive rate of pathogens causing severe community acquired pneumonia(sCAP),according to autopsies researches.Owing to a lack of valuable tools for detecting pathogens,a number of patients with sCAP had not received properly targeted therapy. LAMP is a recently developed nucleic acid amplification technique.The unique advantage of LAMP is not only the straightforward operation, low requirements for needing equipment,but also the shortness reaction time.LAMP is suitable for the early detection of common pathogens.Objective:To verify the Effectiveness and feasibility of LAMP for detecting common pathogens.Method:The target patients were confirmed sCAP. Sputum or bronchus-alveolar lavage fluid was collected at the first day.LAMP and sputum culture were performed to detect 12 kinds of common pathogens. We calculated the sensitivity, specificity and accuracy of LAMP for diagnosis common pathogens causing sCAP,as sputum culture served as a standard test method.Result:In 79 patients,28 cases(35.44%) were positive by the standard test. When we took 2.95 as the cut-off point, the AUC was up to 0.871 (95%CI 0.777-0.936, P<0.05);the sensitivity, specificity and their 95%CI were 96.4%(81.7-99.9) and 68.63%(54.11-80.89).The performance of LAMP was as follows:agreement 79.1%;sensitivity 96.4%; specificity 68.6%; positive-predictive value 80.0%; negative-predictive value 98.0%.The average DNA concentration(lg10 copies/ml) was (4.3±0.9) in the 28 positive cases, while the number was (2.5±1.6) in the 51 negative cases (P<0.05). The most common detected pathogens by LAMP were Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii and maltophilia Aeromonas.The Spearman correlation coefficient among DNA concentration, PCT and WBC were 0.73 (95%CI 0.60-0.82,P<0.05).0.42 (95%CI0.21-0.59,P<0.05)Conclusion:1.LAMP can be used as a mean of detecting common pathogens in sCAP patients.2.The pathogen DNA concentration of positive specimans by the standard method is significantly higher than that of negative specimans.3. Pathogen DNA concentration has obviously positive correlation with PCT and white cell count.