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1	Philosophy and Approach to Diagnostic Parasitology

With the expansion of world travel and increased access to more varied geographic areas and populations, medical and laboratory professionals will continue to see more “tropical” diseases and infections in nonendemic areas. This is due to the rapidity with which both people and organisms can be conveyed from one place to another. Travel has become available and more affordable for many people throughout the world, including those who are in some way compromised in terms of their overall health status. The increased transportation of infectious agents, as well as potential human carriers, has been clearly demonstrated, particularly via air travel. It has also been well documented that vectors carrying parasitic organisms can be transported via air travel in baggage and in the unpressurized parts of the plane itself; once released, these infected vectors can then transmit these parasites to humans, even in nonendemic areas.

With the continued increase in the number of patients whose immune systems are compromised through either underlying illness, chemotherapy, transplantation, AIDS, or age, we are much more likely to see increasing numbers of opportunistic infections, including those caused by parasites. Also, we continue to discover and document organisms once thought to be nonpathogenic that, when found in the compromised host, can cause serious disease. In considering the potential causes of illness in this patient population, the possibility of parasitic infections must always be considered as part of the differential diagnosis.

Diagnostic procedures in the field of medical parasitology require a great deal of judgmental and interpretative experience and are, with very few exceptions, classified by the Clinical Laboratory Improvement Act of 1988 (CLIA ’88) as high complexity procedures. Very few procedures are automated, and organism identification relies primarily on morphologic characteristics that can be very difficult to differentiate. Although parasite morphology can be “learned” at the microscope, knowledge about the life cycle, epidemiology, infectivity, geographic range, clinical symptoms, range of illness, disease presentation depending on immune status, and recommended therapy is critical to the operation of any laboratory providing diagnostic services in medical parasitology.

The basic approach to diagnostic parasitology should be no different from that used in other areas of microbiology. There are guidelines published by the American Society for Microbiology (1–5), the American Society of Parasitologists (6), the American Society for Medical Technology (7), the College of American Pathologists (8), and the Clinical and Laboratory Standards Institute (formerly National Committee for Clinical Laboratory Standards) (9–16) that contain recommended procedures for this field. If these general guidelines and recommendations are not followed, there is some question as to the qualifications of the laboratory performing the diagnostic work. At the very least, the clinician should be informed about the limitations of the procedures that are being used. These guidelines are also accompanied by specific regulations for a number of laboratory issues and include CLIA ’88 and requirements related to safety and protection of employees from blood or blood-borne pathogens (standard precautions) (17–20).

Because it is difficult for medical staff to maintain expertise in every available diagnostic procedure within microbiology, it is mandatory that close communication exist between the laboratory and clinicians. Frequent and complete communication, particularly concerning appropriate test orders and the clinical relevance of any diagnostic procedure within the context of total patient care and quality assurance, is very important. Therapeutic intervention often depends on results obtained from these procedures; therefore, the clinician must be aware of the limitations of each test method and the results obtained. This information becomes particularly important when one is discussing the patient’s history and the recommended number and types of specimens to be submitted for examination.

During the past few years, there has been an increased awareness of the importance of having trained and qualified personnel perform these diagnostic procedures. There has been a concerted effort among many individuals and institutions in this country to upgrade the level of teaching and to bring to the medical community’s attention the need for individuals who are familiar with diagnostic parasitology. With many laboratories decreasing staff size as a cost-containment measure, we are also seeing more “generalists” who are rotating throughout many sections of the laboratory, not just microbiology. Although necessary because of managed-care constraints and continued growth of capitated contracts, this approach contributes to the difficulties in maintaining well-trained staff in some of the specialty areas of microbiology. It becomes even more important to provide well-written laboratory protocols and to standardize test methods for consistency. There has also been increased awareness within the medical community of the need for additional training in the area of infectious diseases for the clinician and laboratory technician alike. This need has been reflected in the number of workshops, seminars, and publications that are available. The integration of information among all members of the health care team has certainly improved in terms of overall patient care.

The field of microbiology has taken on additional relevance and importance for a number of other reasons. Improved means of travel has made the world a smaller place. An individual’s chances of exposure to parasites not endemic to his or her homeland and the possibility of acquiring or transmitting certain infections have been increasing. These facts emphasize the need to take a correct and complete history from a patient. It is important to be aware of the organisms commonly found within certain areas of the world and the makeup of the patient population being serviced at any particular health facility.

The most important step in the diagnosis of parasitic infections is the selection and submission of the appropriate clinical specimen within specified time lines and according to set protocols (21–23).

It is also important for the physician to know the efficacy of any diagnostic technique for parasite recovery and eventual diagnosis. Our approach to testing is undergoing continuous review, particularly within the current health care environment and cost-containment initiatives. The issue of patient care becomes particularly important when we begin to examine the number and types of compromised patients now being seen in all facilities. The increased publicity concerning immunocompromised patients has led to a greater awareness of parasitic infections in this patient population, regardless of the original cause of the immune deficiencies. Many of these patients with immune system defects are particularly at risk, whether because of previously acquired infections that have remained latent for many years or because of susceptibility to new infections. Many of these infections may present with unusual symptoms, and some are relatively new disease entities or those that are less commonly encountered (microsporidiosis, granulomatous amebic encephalitis, and infection with Cyclospora cayetanensis).

Often in other areas of microbiology, therapy is begun on the basis of patient history and symptoms. This approach is generally not recommended or used in cases of parasitic infection. Thus, the understanding of the characteristics of any parasitic infection (general geographic range, life cycle, clinical disease, diagnostic methods, therapy, epidemiology, and control) and the use of appropriate diagnostic procedures accompanied by a complete understanding of the limitations of each procedure become very important. Because of this approach to patient care, the general consensus among individuals within the field of diagnostic medical parasitology is that the use of certain incomplete procedures may result in incorrect information for the physician and may ultimately compromise patient care.

The main emphasis should be on the importance of understanding and recognizing potential parasitic infections, submitting the appropriate number and type of clinical specimens, knowing what procedures may provide confirmation of the diagnosis, and recognizing the implications and limitations of information provided to the physician. With the current emphasis on the development and use of molecular methods, understanding the benefits and limitations of these procedures will be critical to patient care outcomes. If there is an incomplete understanding of the requirements for high-quality diagnostic testing, incomplete information will be transmitted to the clinician. It is the responsibility of both the laboratory and the clinician to develop a greater awareness of the importance of these requirements.

References

1. Garcia LS (ed). 2010. Clinical Microbiology Procedures Handbook, 2nd ed. ASM Press, Washington, DC.

2. Isenberg HD (ed). 2004. Clinical Microbiology Procedures Handbook, 2nd ed., p. 9.0.1–9.10.8.3. ASM Press, Washington, DC.

3. Isenberg HD (ed). 1995. Essential Procedures for Clinical Microbiology. ASM Press, Washington, DC.

4. Garcia LS, Johnston SP, Linscott AJ, Shimizu RY. 2008. Cumitech 46, Laboratory procedures for diagnosis of blood-borne parasitic diseases. Coordinating ed, Garcia LS. ASM Press, Washington, DC.

5. Garcia LS, Smith JW, Fritsche TR. 2003. Cumitech 30A, Selection and use of laboratory procedures for diagnosis of parasitic infections of the gastrointestinal tract. Coordinating ed, Garcia LS. ASM Press, Washington, DC.

6. Committee on Education, American Society of Parasitologists. 1977. Procedures suggested for use in examination of clinical specimens for parasitic infection. J Parasitol 63:959–960.

7. Parasitology Subcommittee, Microbiology Section of Scientific Assembly, American Society for Medical Technology. 1978. Recommended procedures for the examination of clinical specimens submitted for the diagnosis of parasitic infections. Am J Med Technol 44:1101–1106.

8. College of American Pathologists. 2012. Commission on Laboratory Accreditation Inspection Checklist. College of American Pathologists, Chicago, IL.

9. Clinical and Laboratory Standards Institute. 2005. Procedures for the Recovery and Identification of Parasites from the Intestinal Tract, 2nd ed. Approved guideline M28-A2. Clinical and Laboratory Standards Institute, Wayne, PA.

10. Clinical and Laboratory Standards Institute. 2005. Protection of Laboratory Workers from Occupationally Acquired Infection, 3rd ed. Approved guideline M29-A3. Clinical and Laboratory Standards Institute, Wayne, PA.

11. Clinical and Laboratory Standards Institute. 2000. Laboratory Diagnosis of Blood-borne Parasitic Diseases. Approved guideline M15-A. Clinical and Laboratory Standards Institute, Wayne, PA.

12. Clinical and Laboratory Standards Institute. 2005. Procedures for the Recovery and Identification of Parasites from the Intestinal Tract. Approved guideline M28-A2. Clinical and Laboratory Standards Institute, Wayne, PA.

13. Clinical and Laboratory Standards Institute. 2004. Clinical Use and Interpretation of Serologic Tests for Toxoplasma gondii. Approved guideline M36-A. Clinical and Laboratory Standards Institute, Wayne, PA.

14. Clinical and Laboratory Standards Institute. 2012. Clinical Laboratory Safety. Approved guideline GP17-A3. Clinical and Laboratory Standards Institute, Wayne, PA.

15. Clinical and Laboratory Standards Institute. 2009. Training and Competence Assessment. Approved guideline GP21-A3. Clinical and Laboratory Standards Institute, Wayne, PA.

16. Clinical and Laboratory Standards Institute. 2011. Clinical Laboratory Waste Management, 3rd ed. Approved guideline GP5-A3. Clinical and Laboratory Standards Institute, Wayne, PA.

17. Code of Federal Regulations. 1987. Update May 27, 1992. Title 29, parts 1910.1200 and 1910.1296. U.S. Government Printing Office, Washington, DC.

18. Code of Federal Regulations. 1989. Title 29, part 1910.106. U.S. Government Printing Office, Washington, DC.

19. Code of Federal Regulations. 1989. Title 29, part 1910.1200. U.S. Government Printing Office, Washington, DC.

20. Code of Federal Regulations. 1989. Title 29, part 1910.1450. U.S. Government Printing Office, Washington, DC.

21. Garcia LS. 2009. Practical Guide to Diagnostic Parasitology, 2nd ed. ASM Press, Washington, DC.

22. Joint Commission. 2013. Survey Activity Guide for Health Care Organizations, 2013. The Joint Commission, Chicago, IL.

23. Garcia LS (ed). 2013. Clinical Laboratory Management, 2nd ed. ASM Press, Washington, DC.