Effective use of the clinical microbiology laboratory for diagnosing diarrheal diseases.

Abstract

Diarrheal diseases are an enormous problem worldwide and cause considerable morbidity and mortality, especially in developing nations. Four times as many diarrhea-related deaths occur worldwide in a single day than occur in an entire year in the United States [1, 2]. Individuals who are at greater risk for developing diarrheal diseases than other segments of the population, especially in developed countries, include those in daycare centers, travelers, and patients with HIV infection. During the past decade, the HIV epidemic has resulted in a relatively large number of persons at high risk for developing infectious diarrhea, particularly that due to organisms heretofore unrecognized or unheard of in immunocompetent patients. As the number of potential etiologic agents of diarrheal disease increases, the clinical microbiology laboratory takes on an increasingly important role in identifying these agents. Of the many tests performed in the clinical microbiology laboratory, there is virtually no more labor-intensive and costly routine test than that of the stool culture and parasitological examination. The microbiological workup of stool requires a specific algorithm to isolate and identify pathogens. Factors including the number of special media required, the labor intensiveness of the process, and the generally low sensitivity of stool cultures combine to make this test one of the most expensive diagnostic tests offered; the cost ranges from $100 to more than $100,000 per positive result, depending on the tests performed, the prevalence of disease, and number of samples tested [3-5]. While stool cultures and parasitological examinations are invaluable tools for epidemiological studies, the role of these cultures in the management of acute diarrhea has not been well defined because many episodes of acute diarrhea are self limited. It is estimated that >4 million tests for bacteria and parasites are performed in the United States annually; thus, efficient use of the laboratory in an era of cost containment is critical [6]. The purpose of this paper is to review the current understanding and limitations of the clinical microbiology laboratory in the management of diarrheal illness and to dispel