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Although not all infectious diseases require a diagnostic laboratory intervention (eg, uncomplicated otitis media), clinicians often rely on laboratory tests to help identify a causative agent, select an appropriate antimicrobial agent, and/or assess response to therapy. It is imperative that clinicians have a basic understanding of diagnostic microbiology so they can obtain appropriate samples and order the most appropriate test for diagnosing the condition they are suspecting and selecting the most appropriate therapy (Table 226-1). Often, consultation with the microbiology laboratory is useful to determine which test would be most appropriate for the suspected disease.

Table 226-1. Useful Tips from the Microbiology Laboratory

It is important to recognize that molecular biology has influenced the way in which infectious diseases are diagnosed.49 DNA and RNA amplification by PCR has become an important resource in the diagnosis of infections. PCR has been shown to be more sensitive than in situ hybridization. It can detect as few as 10 to 100 copies of nucleic acid, whereas hybridization detects only 10,000 copies. PCR has been useful for identifying slow-growing organisms such as Mycobacterium tuberculosis and Borrelia burgdorferi; Rickettsia, and, potential agents of bioterrorism.153 Molecular fingerprinting has become a useful resource in the investigation of nosocomial infections and has fostered the field of molecular epidemiology.154-156

Collection and Processing of Clinical Specimens

No degree of laboratory expertise can correct the error of inappropriately collected and transported specimens. The proper collection and handling of clinical specimens is as important as selecting the correct medication for treatment.1,2 Common problems with clinical ...

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