Diagnostics: The Role of the Laboratory

The significant role of the laboratory in infectious disease diagnosis calls for a closed loop working relationship between the physician and laboratory technician. The laboratory aims to generate useful information for the diagnosis, prognostication, and therapeutic monitoring of many human conditions. The laboratory and physician’s combined role holds an immense value for the healthcare system as a whole, especially in the critical care unit. This chapter focuses on the role the laboratory plays in critical care medicine. It will help allow physicians to focus on tests that are valuable and understand tests that add little or no value for diagnostic decisions. This chapter will focus on an organism-based approach as opposed to a system-based approach and includes laboratory testing for viral, bacterial, fungal, and parasitic infections. Each section will contain introductory concepts, a summary of key points, the most reliable tests to order, samples to collect in order of preference, specimen transport devices, procedures, temperatures, and detailed notes on specific issues regarding test methods. This chapter is designed to serve as a tool for physicians in choosing tests that will aid them in accurately and effectively diagnosing infectious diseases in critically ill patients.