results from other procedures performed in a clinical laboratory can be very helpful when trying to diagnose a parasitic infection. Specific examples might be a routine urinalysis, hematology procedures including a complete blood count, or various chemistry profiles. These results often provide supporting data consistent with a suspect parasitic infection.
What Factors Should Be Considered When Developing Test Menus?
Physical Plant
Provided that equipment requirements are met, most clinical laboratory space designed for microbiology procedures can be used for diagnostic parasitology testing. In smaller facilities, this work can be incorporated into a routine microbiology laboratory. Another consideration is the physical location of the laboratory with respect to the source of clinical specimens. If distance is a consideration, the use of appropriate specimen preservatives must be incorporated into patient specimen collection protocols to ensure that accurate laboratory results will be obtained.
Client Base
Recognition and identification of groups of clients served may dictate the methodology and range of diagnostic testing available. Requests for testing for parasites may be minimal within a hospital setting where many procedures are related to elective surgery. In contrast, test requests originating from a large medical center with extensive outpatient clinics may require a broader range of testing and expertise.
Customer Requirements and Perceived Levels of Service
Depending on the client base, patient complexity, history of test requests, and physician interests, the laboratory may be required to provide minimal testing that includes the most commonly performed parasitology procedures. This type of laboratory would generally not be considered a consultative resource; it would need to identify a consultative laboratory to assist with more unusual tests and/or test interpretations. The range and complexity of available tests would also depend on the laboratory’s definition of its role in the local, regional, national, or international health care arenas.
Personnel Availability and Level of Expertise
Most procedures performed in the diagnostic parasitology laboratory require extensive microscopy training and experience. They are categorized as high-complexity tests by CLIA ’88 and are frequently performed by licensed technologists. Based on microscopy examinations, these procedures require a great deal of interpretation. Although cross-training provides some help with certain procedures, including specimen processing, the necessary interpretive skills are not learned in a week or two and can be easily lost without practice. For this reason, it is important to have a minimum of one or two people who are not only skilled at performing the procedures but also capable of interpreting the findings and providing client training and consultation.
Equipment
The level of equipment required for diagnostic parasitology work is very minimal; however, the one expense that should not be limited would be for one or more microscopes with good optics. Each microscope should be equipped with high-quality (flat-field) objectives (10×, 40×, 50×, or 60×, and 100× oil immersion objectives). The oculars should be a minimum of 10×.
Depending on the range of immunoassay testing available, a fluorescence microscope or enzyme immunoassay reader might be desirable. The availability of this equipment varies tremendously from one laboratory to another, and the equipment may be shared with other groups within the laboratory.
Another option would be a fume hood, in which the staining could be performed; this is not required, but recommended, particularly if the laboratory is still using xylene for dehydration of permanent stained fecal smears.
The rest of the equipment is quite common and can be shared with other areas within the laboratory. Equipment would include refrigerators, freezers, and pipette systems. Often, these can also be shared.
Budget
In general, approximately 70% of a microbiology laboratory budget is related to personnel costs. Although diagnostic procedures in the parasitology area are labor-intensive and may require a microscope with good optics, in general budget costs are minimal. Costs tend to increase if the newer immunoassay procedure kits are brought into the laboratory; however, these increased supply costs may be balanced out by diminished labor costs. Each laboratory will have to decide which procedures to offer, which tests can be performed in a batch mode, how many procedures will be ordered per month, what length of turnaround time is required, whether STAT testing is possible, and what options exist for referral laboratories, as well as taking educational initiatives and client preferences into consideration.
Although diagnostic parasitology can be an important part of the microbiology laboratory, it is just one section within the total laboratory context and should be analyzed as such for cost containment and clinical relevance.
Risk Management Issues Associated with STAT Testing
There are two circumstances in diagnostic medical parasitology that represent true STATs. One is a suspected case of primary amebic meningoencephalitis (PAM) caused by Naegleria fowleri or granulomatous amebic encephalitis (GAE) caused by Acanthamoeba spp., Balamuthia mandrillaris, or Sappinia diploidea, and the other situation is any case where thick and thin blood films are requested for testing for blood parasites, possibly those that cause malaria. Extensive discussions of these organisms can be found in the following reference (L. S. Garcia, Diagnostic Medical Parasitology, 5th ed., ASM Press, Washington, DC, 2007).
Primary Amebic Meningoencephalitis
Amebic meningoencephalitis caused by N. fowleri is an acute, suppurative infection of the brain and meninges. With extremely rare exceptions, the disease is rapidly fatal in humans. The period between contact with the organism and onset of clinical symptoms such as fever, headache, and rhinitis may vary from 2 to 3 days to as long as 7 to 15 days.
The amebae may enter the nasal cavity by inhalation or aspiration of water, dust, or aerosols containing the trophozoites or cysts. The organisms then penetrate the nasal mucosa, probably through phagocytosis of the olfactory epithelium cells, and migrate via the olfactory nerves to the brain. Data suggest that N. fowleri directly ingests brain tissue by producing food cups or amebostomes, in addition to producing a contact-dependent cytolysis which is mediated by a heat-stable hemolytic protein, heat-labile cytolysis, and/or phospholipase enzymes. Cysts of N. fowleri are generally not seen in brain tissue.
Early symptoms include vague upper respiratory distress, headache, lethargy, and occasionally olfactory problems. The acute phase includes sore throat, stuffy blocked or discharging nose, and severe headache. Progressive symptoms include pyrexia, vomiting, and stiffness of the neck. Mental confusion and coma usually occur approximately 3 to 5 days prior to death. The cause of death is usually cardiorespiratory arrest and pulmonary edema.
PAM can resemble acute purulent bacterial meningitis, and these conditions may be difficult to differentiate, particularly in the early stages. The CSF may have a predominantly polymorphonuclear leukocytosis,
