1 - CHARACTERISTICS OF THE VIAL
The sample volume delimited by the PARATEST™ collector is approximately 1 ml (or 1 gram) and it is recommended that two portions of the collector cone be collected, equivalent to a total of 2 g. This is the volume recommended by good scientific manuals, and it is absolutely sufficient for the examination, since also that quantity has already been tested and validated in comparison with the method of Hoffman et al.
The filter holes are 266 micrometers in diameter, which have been carefully calculated to retain the coarsest debris (using the same function as the gauze or sieve of other methods) and to allow the passage of all the elements necessary for the examination (protozoan cysts, eggs and larvae of helminths).
In no case this should be done. Because proper flushing of the vial is very delicate and laborious, eggs, larvae or cysts are especially likely to be trapped, especially in the filter and cap, causing cross-contamination of the following samples and generating false positive results. Therefore, never reuse the PARATEST™ vial.
The collection method is simplified for the patient and, for the technicians, PARATEST™ offers a much cleaner filtration, eliminates bad odor, prevents contamination, ensures biosafety (closed system), reduces space and the time of execution of the exam (possibility to perform ten times more tests when compared to the method of Hoffman).
2 - PRESERVATIVE LIQUID
The preservative fluids present in the three products of the PARATEST™ Family have the property of fixing and maintaining the integrity of egg structures, larvae and cysts for long periods (Greenfix™ - 15 days, Formalin and SAF - 30 days). In addition, they have the function of diluent, enabling the patient to perform the dilution soon after collection, by means of shaking the vial.
PARATEST™ should not be used to evidence blood in the stool, since the samples are diluted in liquid preservatives that may promote pre-analytical errors in the occult blood tests.
3 - SAMPLE COLLECTION AND DILUTION
The language and the drawings were prepared in order to facilitate understanding. If any patient presents difficulties, it is suggested that the attendant responsible provide all necessary supplementary instruction, having in hand an already open PARATEST™ vial with which to explain in more detail.
The quantity of 02 (two) grams defined by 02 (two) measures of the collector allows a certain tolerance. But if the fecal mass deposited inside the vial is much higher than the measure, there may be interference in the quality of the filtrate obtained after the concentration. It is for this reason that the instructions for collection recommend avoiding excessive sampling. Explain clearly to the patient that it is sufficient to deposit the fecal mass indicated in the collection instructions of the PARATEST™ SYSTEM into the vial.
It is recommended that stool portions to be collected and subsequently diluted in the PARATEST™ SYSTEM preservative liquid are not collected directly from the toilet.
There are cases of constipation, which are quite rare, in which the stools become very dry, which makes it difficult to fully apply the norms for targeted collection and dilution. In such cases, it is recommended that the patient use some sturdy instrument to separate a portion of feces of approximately equivalent volume to that which would fit in the collector. This portion may be placed directly into the vial, which must be shaken several times with a time interval between shaking to achieve complete dilution of the sample.
When stool consistency is normal, the recommended stirring in the instructions is enough for the sample to stand out from the collector and dilute in the preservative liquid. But it is always possible that some patient does not follow the instructions completely, leaving the dilution incomplete. This can easily be noticed by the technician by observing the inside of the bottle by transparency. When they arrive in the laboratory, even the driest samples are already quite soft, facilitating complete dilution. The laboratory that has a Kline shaker can use it for agitation of PARATEST™.
The filtrate obtained from 2 (two) grams of feces allows the preparation of several slides. Ideally, the sample should be completely diluted, but if a part of the sample is not dissolved, there will still be sufficient filtration for the examination. Feces may contain badly digested foods that do not dissolve upon shaking. Such structures are generally useless for examination and will be retained by the PARATEST™ filter.
4 - SERIAL SAMPLES
The collection of SERIAL SAMPLES (03 samples) is the collection of feces in three different periods. Held at intervals of a few days, due to the life cycle of some parasites that may not be detected on a given day but are in another moment with a short time. Thus, a growing number of laboratories have been requesting that the collection of three samples on alternate days be carried out so as to ensure greater prevalence or not of cyclic parasites.
DK Diagnostics™ recommends that three vials must be given to the patient and used for each collection, i.e., one vial for each day of collection. In each vial the patient will place two measurements of the PARATEST™ collector, according to collection instructions.
5 - METHODS OF CONCENTRATION
Yes. The simplicity offered by the PARATEST™ SYSTEM is unique, making the routine of parasitological examination so quick and efficient that technicians can transfer this time gain to more complex exams.
Yes. The spontaneous sedimentation method used by the PARATEST™ System has been tested and proven effective compared to other, much more laborious and complex methods.
Microscopic examination, especially on poor specimens, requires the search and identification of eggs, larvae, and cysts in the midst of other structures of no interest. With the PARATEST™ filtration system, the debris is retained much more effectively, making filtration cleaner and easier to examine.
The PARATEST™ method allows the optimized diagnosis of practically all the most common helminth and protozoan species in human parasitism in our environment. Helminth eggs and larvae, as well as cysts and protozoan trophozoites, are found without difficulty in microscopic examination.
We know of no limitations that would invalidate the method for any kind of intestinal parasite. Eggs, larvae and cysts detectable by other methods are more easily detected by PARATEST™.
For the routine needs, the method we recommend fully satisfies, because it offers excellent recovery of the most common intestinal parasitic forms in the human species. There is no pretense of completely replacing all methods, as there are some very specific ones that cannot be overlooked (e.g., anal-swab, for Enterobius vermicularis).
6 - SAMPLE EXAMINATION
The larger the volume of filtrate examined, the greater the chances of finding the parasites, especially in samples with a small number of parasitic forms. The result can be considered reliable when examining the entire slide, obtained with a drop of covered foil filtrate of approximately 24x24 mm. Depending on the SOP (Standard Operating Procedure) of the laboratory, it is advisable to examine the slides in triplicate, as is recommended for any other method.
PARATEST™ is a qualitative method. Quantification should be done by using specific methods for such, such as Kato-Katz Method and Stoll Method.
False negative results can occur with any method of concentration. This is also possible with PARATEST™, not because of the intrinsic limitation of the method. Examples: a) When the patient is harboring only male parasites, eggs cannot be found in the feces; b) When the elimination of cysts, eggs and larvae are cyclic, the collection may coincide with a period of absence of these elements; c) Eggs of some species, such as Pinworm and Taenia, are rarely eliminated with feces; d) If the number of parasites is small, it may be difficult to detect their presence by examining the feces; e) The use of antibiotics, antacids and radiological contrast may inhibit egg laying; f) Some species (Cryptosporidium) require special coloring.
None of the parasitological methods available in the national and international market reaches 100% sensitivity. This fragility applies to any method, whether spontaneous sedimentation, centrifugal sedimentation or flotation methods.
The results of the comparative studies between methods performed in triple-blind by DK Diagnostics™ were: study 1) PARATEST™: sensitivity 91.10%; Hoffman: sensitivity 88.30% and Ritchie: 85.50%. Study 2) PARATEST™: 64.0% and Faust 60.0%.
Because of the known fragility of all coproparasitological methods, WHO recommends the reading of three slides of the same sediment as a way to increase the sensitivity of the parasitological diagnosis. Ideally, for any method, three slides should be analyzed microscopically.