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Chapter 40 : PCR as a Routine Method for Diagnosis of Legionnaires' Disease
This chapter evaluates the performance of PCR with respect to sensitivity, specificity, and predictive value of a positive test result with the help of the results obtained by other Legionella diagnostic methods used in a routine laboratory. Laboratory results for other diagnostic methods were included if samples were collected within a period of 90 days relative to the sample for PCR. The amplification control thus contained the binding sites of the 16S rDNA primers, was purified by gel electrophoresis, and was added to the mastermix at a concentration producing a distinct amplicon in negative controls without increasing the level of detection for the positive controls. The amplicons of the Legionella PCR were analyzed by gel electrophoresis. The authors used two different assays: from 1995 to 1999 an inhouse assay was used and from 1999 the Biotest Legionella Urin antigen EIA was used. The performance of Legionella PCR as a routine diagnostic method for respiratory infections (Legionnaires' disease) caused by L. pneumophila was acceptable, although not all PCR- positive cases could be verified by other diagnostic methods. The sensitivity of Legionella PCR is probably higher than any other single method.