Page 17 - parasitology for medical and clinical laboratoryprofessionals

PREFACE xv

human parasites are easily visualized, particularly those properly timed and performed specimen collection are
of intestinal parasites known as worms. The protozoal of the utmost importance. Most important pathogens are
types are more difficult to distinguish from tissue and found either in the blood or in the stool, although other
blood cells for identification purposes. It might be noted anatomic sites are of significance. A properly collected and
that some parasites of domestic animals may resemble preserved stool specimen is examined by use of the micro-
those of humans, with only subtle differences. Indirect scope for detecting parasites and their eggs if appropriate.
identification would most often be a serological test, Some microorganisms are found in the bloodstream and
using the serum from a patient’s blood, and testing for of course require proper collection and treatment of blood
the production of antibodies that are stimulated by a par- smears for examination to determine infections of certain
ticular organism. Serological tests for many parasites are intracellular parasites. Serological tests for antibodies
not currently available, but perhaps more indirect and formed by the body against specific parasites are available
definitive tests will eventually be developed. for a few parasitic organisms at this time.

Prevalence of Parasitic Quality Assurance
Infections The purpose of a quality assurance program is to provide

assurance that accurate and reproducible results are pro-
A number of organisms that were not originally
considered as being parasites may be a result of a para- duced, from collection and transport of the sample and
the initial handling of the specimen. These steps require
sitic infection, where alterations have occurred in the
gastrointestinal system. Certain yeasts may grow as a that other health care professionals who provide direct
patient care will adhere to correct practices to insure the
result of dysbiosis, a condition resulting from a disor-
der of the normal flora in the intestines. Although fungi, best results possible. In addition, the technical worker,
usually a laboratory professional, is enabled to trouble-
yeasts, and molds are not strictly a human parasite, there
are similarities between the two groups. Candida, a com- shoot and correct any problem areas in the analysis of
the samples and the reporting of accurate results. Quality
mon yeast, often occurs in both pathogenic bacterial
and parasitic infections. Parasitic infections appear to assurance for parasitology is somewhat different than
some of the automated procedures in the laboratory,
be more prevalent than most health care professionals
would think in this country. Outpatients at a gastroenter- and requires a great deal of critical thinking, attention to
details, and even making assumptions at times. Factors
ology clinic in Elmhurst, New York, were diagnosed with
parasites at a rate of 74 percent in one 2002 report and affecting the quality of results include environmental con-
ditions, training and competence of practitioners, and
a total of 20 percent of this group also yielded positive
findings for other pathogens (Farr). In the same report, availability of adequate supplies and operable equipment.
Quality control is but a component of a good qual-
public health laboratories reported that 15.6 percent
of specimens examined contained at least one parasite. ity assurance program, and prepared slides are available
for laboratory workers to stain and to examine for known
At the Great Smokies Diagnostic Laboratory, almost
30 percent of specimens examined were positive for a parasitic organisms. Adequate performance includes
preparation and staining, as well as identifying parasitic
parasite (Farr, 2002). It is possible that the rate is much
higher, as it required a great deal of diligence to properly organisms. Serological testing for antigens and indirect
tests for the presence of antibodies may also be done on
collect, prepare, and examine specimens to determine
parasitic infections. control specimens to determine effectiveness and compe-
tence of the procedures and the testing personnel.
A common belief of many is that the quality of
Laboratory Tests for laboratory results solely depends upon the particular
Identification of Parasites laboratory performing an analysis. However, this in-
and Their Ova cludes the analytical portion of quality assurance, but
no less important are a number of pre-analytical and
Body fluids and tissues are often specific for certain para- post- analytical factors which influence the quality of the
sitic organisms. Therefore, the proper specimen and the results obtained by the laboratory and its professionals.