COLLECTING, PRESERVING, AND PROCESSING CLINICAL SPECIMENS
Section I. OVERVIEW
The precise laboratory diagnosis of parasitic infections is dependent on the
manner in which the clinical specimens are handled. To obtain the maximum diagnostic
information from clinical samples, the specimens must be processed in such a manner as
to minimize deterioration and distortion. Today, the most reliable method of
parasitological diagnosis is the direct examination of clinical samples. Indirect methods,
such as serological and skin tests, are being introduced into the market at a rapid pace.
These methods, while also reliable, are not as routinely employed as the already
established direct observation procedures, using microscopic or macroscopic
identification procedures. In some instances, examination is not possible within a short
period of time. Therefore, preservation of the sample is imperative to retain the "in vivo"
appearance of parasites. There are factors that affect the success in accurate laboratory
diagnosis. One important factor is having an adequate number of well-trained personnel.
Another factor is the availability of supplies and facilities. Perhaps the most important
factor is the proper collection and satisfactory processing of clinical specimens.
TYPES OF SPECIMENS
The specimens usually obtained for laboratory identification of organisms parasitic
to man are: blood, stool, exudates, aspirations, tissue biopsies, urine, sputum, and
discharges from the vagina and urethra. Stages of parasites can also be identified from
soil, water, insects, and samples from animal or vegetable sources.
PRESERVATIONS OF SPECIMENS
Clinical specimens must be preserved in order to maintain the integrity
and features of parasites they may contain. The solution that preserves all kinds of
specimens has not been developed. Therefore, you can choose from various methods
and techniques depending on the sample you wish to preserve. Different clinical
specimens require different methods of preservation (to be discussed at a later time).
Many laboratory procedures have been developed to ease the identification of
parasites. Every laboratory must have a standard operating procedure (SOP) that
provides technicians with guidelines to follow in performing specific procedures. The
more methods of examination available to the laboratory, the better the recovery of
parasites. The choice among these methods must be dependent upon the sources
available and must meet the local needs and conditions.