[Discussion] MODULE 1 UNIT 4 Flashcards
- Based on symptoms, history
Clinical Diagnosis
- Through physical examination
Clinical Diagnosis
- Use of laboratory tools for specific identification
Laboratory Diagnosis
- demonstration of the parasite (e.g., adults, eggs, larvae, cysts, or trophozoites), or parasite components (e.g., antigens and DNA) in the specimen
Direct method
This provides definitive diagnosis of parasitic infection.
Direct method
- tests for the evidence of parasitic infection other than actually finding the organism itself
Indirect method
This provides only presumptive evidence of infection.
Indirect method
- Parasitic infections are usually diagnosed by examination of a specimen/material under the microscope.
Microscopic Method
Microscopic Method is basically a two-step process:
i. detection of the parasite
ii. identification based on distinctive morphologic characteristics.
- the most common procedure performed in the area of parasitology is the examination of a stool specimen for ova and parasites (O&P exam)
Direct microscopy
- ova - refers to the egg stage of select parasites and parasites encompass the other morphologic forms that may be present.
Direct microscopy
- Appropriate specimen is examined microscopically for parasite diagnostic stage by:
• direct wet mounts • wet mounts of concentrates • permanent stains
Direct microscopy spps
• Cysts & trophozoite of Entamoeba histolytica
• Cysts & trophozoites of Giardia lamblia
• Balantidium coli
• Oocysts of Cystoisospora belli, Cryptosporidium parvum
• Oocysts of Cyclospora cayetanensis, Sarcocystis spp
• Unembryonated egg of Ascaris lumbricoides, & embryonated egg Ascaris lumbricoides
• Eggs of Trichuris trichiura and Diphyllobothrium latum
• Eggs of Capillaria philippinensis and Taenia spp
• Eggs of Hymenolepis nana and Dipylidium caninum
• Eggs of Fasciola spp. and Fasciolopsis busk
• Eggs Schistosoma japonicum, Schistosoma manson
• Rhabditiform larvae of Strongyloides stercoralis
- The gold standard in the diagnosis of common protozoan & helminth infections.
Direct microscopy
- Simple, low cost
Direct microscopy
Direct microscopy- low sensitivity: when parasites are low in numbers such as in:
• light infections • during pre-patent • chronic periods of infection- may yield false negative results
Direct microscopy problem
Concentration technique
Perianal swab – Graham scotch tape method
Enterobius vermicularis (pinworms)
Direct microscopy
• Blood –
Plasmodium spp., Trypanosma spp
Direct microscopy
Sputum
Strongyloides stercoralis
Culture methods using xenic or axenic media have been described for some protozoan parasites
• Trichomonas vaginalis • Leishmania spp. • Trypanosoma cruzi • Entamoeba histolytica • Acanthamoeba spp • Naegleria fowleri.
Culture technique is not routinely done due to:
• infrequent requests • lack of familiarity with methods • the need for special equipment, supplies, & reagents, and • the waiting period for several days or weeks for the result
- Inoculation of a suspected specimen into a laboratory-bred, parasite-free animal
Xenodiagnosis
Specimen may also be examined grossly for parasite stage that are large enough to be seen by the naked eye, such as some
adult worms, and proglottids of tapeworms
- Permits batch processing
IMMUNODIAGNOSTIC METHODS
- Do not require experienced microscopists
IMMUNODIAGNOSTIC METHODS
- Detects the specific antigen unique to the parasite if present in the specimen
Antigen detection
- Detects the specific antibody produced by the body after exposure to the parasite
Antibody detection
- A positive test result is indicative of current infections
ANTIGEN DETECTION
- Superior sensitivities and specificities, easy to use, quick turnaround times
ANTIGEN DETECTION
ANTIGEN DETECTION for Plasmodium
Example: Malarial kits
Specimen: Serum/Whole blood
AG detection indicate specific species of
Plasmodium
ANTIGEN DETECTION for E. histolytica/dispar
Specimen: Stool
Example: ELISA
ANTIGEN DETECTION for T. vaginalis
Specimen: Vaginal discharge
Example: ELISA
ANTIGEN DETECTION for W. bancroft
Example: Immunochromatographic test
Specimen: Whole blood, Plasma, Serum
- determine the presence of antibodies
ANTIBODY DETECTION
immune response formed against parasitic antigens, to provide evidence of infection
antibodies
ANTIBODY DETECTION ADVANTAGES:
- recommended in the diagnosis of:
Parasitic infections that reside in the host’s deep tissues
occult infections
- may provide early detection when significant levels of antibodies are produced before the patent stage.
ANTIBODY DETECTION
- in some people, parasitic infections may not stimulate antibody response or seroconversion may be delayed with onset of clinical symptoms
ANTIBODY DETECTION
- A false positive test may be produced when examining individuals from endemic areas
ANTIBODY DETECTION
- does not distinguish between active and previous infection because antibodies may decline slowly and persist even after cure
ANTIBODY DETECTION
- low sensitivity and specificity
ANTIBODY DETECTION
high levels of sensitivity and specificity for parasite identification
Nucleic acid amplification tests (NAATs)
• ability to differentiate morphologically similar organisms
MOLECULAR TECHNIQUE
• lack of reliance on subjective microscopic features
MOLECULAR TECHNIQUE
• may also be used to monitor the success of antiparasitic therapy
MOLECULAR TECHNIQUE
are performed by injecting parasitic antigen intradermally and observing the reaction
Skin tests
response is seen within 30 minutes of infection in immediate hypersensitivity reaction
wheal and flare
response is seen within 48 hrs of infection in delayed hypersensitivity reaction
erythema and induration
• Montenegro test:
Kala-azar (Leishmania donovani)
• Bachman intradermal test:
Trichinellosis (Trichinella spiralis)
• Casoni’s test:
Hydatid disease (Echinococcus granulosus)
These tests are used to look for some parasitic diseases that may cause lesions in the organs.
Radiologic examination
X-Ray spp
Diphyllobothrium latum
Radiologic examination types
Ultrasound
MRI
is a guarantee that the information in the laboratory result can be relied upon by the physician to confirm or rule out parasitic infections
QUALITY ASSURANCE
PRE-ANALYTICAL PHASE includes
a. Test ordering and request forms
b. Proper specimen collection, storage, and transport
c. Specimen receipt and accessioning
d. Training of personnel
Test ordering and request forms include
• source/type of the sample
• patient’s name and identification number
• The physician’s name
• and the date and time of sample collection
• Correct type of specimen and/or (?) of specimen collection
• Appropriate (?)
• (?). Certain medications and substances may interfere with the detection of parasites, thus should be avoided starting days before and continuing through the test period.
• Acceptable amount or (?) of the specimen
• Manner of specimen collection, storage, transport
• Proper specimen (?) (source/type of specimen the patient’s name and identification number, the physician’s name, and the date and time of sample collection)
• Use of (?)
• (?) from sample collection to receipt and examination in the laboratory.
time
specimen container
Patient preparation
volume
labelling
preservatives
Time frame
A record system is maintained to track the specimen received into the laboratory.
Specimen receipt and accessioning
The person performing the parasitologic examination must be familiar with appropriate technical procedures to be used for each type of specimen and morphologic recognition and differentiation of parasites.
Training of personnel
ANALYTICAL PHASE includes
Standard operating procedures (SOP)
Reference Materials
Equipment
Reagents and supplies
Personnel
Standard operating procedures (SOP)
-Instructions for proper (?) of specimens
-Criteria for (?) of specimens
-Preparation of (?)
-Equipment (?)
-Detailed description of (?)
-Criteria for (?) of parasites
-(?) procedures
-(?) of results
-(?) practices
-Healthcare (?)
collection and handling
acceptance and rejection
maintenance
reagents and solutions
techniques
identification
Quality control
Reporting and interpretation
Health and safety
waste management
Reference Materials
-Reference (?)
-(?) specimens of helminth eggs, larvae, and protozoan cysts
-(?) of helminth eggs, larvae, and protozoan cysts
-(?) of protozoan trophozoites, cysts, and oocysts
-(?) of blood with blood parasites (malaria, filaria
books, manuals, atlases
Formalin-preserved
Temporary mounts
Stained fecal smears
Permanent stained smears
Equipment
-Always follow (?)
-Ensure that all equipment are (?) correctly
-Equipment are maintained on a routine basis by (?) and mechnical maintenance and repair is performed by (?). All data related maintenance and/or repair activities must be recorded
manufacturers manual and instructions
installed and used
laboratory staff; qualified service technician
Reagents and supplies
Certificate of Product Registration (CPR)
Material Safety Data Sheets
Checking of Inventory
Reagent preparation
Personnel
-Each laboratory personnel has the responsibility to perform all (?) in strict accordance with the policies contained in the SOP manual
-there should be adequate and effective (?) for the laboratory personnel
-They must be encouraged to participate in (?) esp. on the use of appropriate parasitological echniques and on morphologic recognition and differentiation of parasites
operational techniques
continuing education program
in-service training, seminar, workshops
• reporting and recording of the stool analysis results are in accordance with the SOP manual
POST-ANALYTICAL PHASE
should be written neatly on the form i.e. the writings readable and understood by the one receiving the results
reports
• All reports are checked and signed by (?) who performed the test before they are issued out
POST-ANALYTICAL PHASE
laboratory staff
are kept in the laboratory for future use or management of the patient in accordance with the clinical laboratory’s retention policy
• Patient data logs
• Results must be released in a timely manner
POST-ANALYTICAL PHASE
defined as “a set of procedures for continuously assessing laboratory work and the emergent results” (WHO, 1981)
Internal quality control (IQC)
This primarily monitors day-to-day accuracy and reproducibility in any procedure
Internal quality control (IQC)
Because this is done locally within the laboratory, corrective action can be done immediately.
Internal quality control (IQC)
are sometimes used interchangeably
quality control (QC) and IQC
A program of evaluation of the laboratory’s performance by an external agency
External quality assessment (EQA)
T or F
Upon unacceptable IQA result identification, the problem must be investigated for possible causes and any necessary corrective action taken
F - EQA
In the Philippines, the EQA program is referred to as (?) that is conducted by a (?)
National External Quality Assessment Scheme (NEQAS)
National Reference Laboratory (NRL)
is the reference laboratory designated to conduct NEQAS in parasitology laboratories
Research Institute for Tropical Medicine (RITM)
Proficiency testing events are given
annually
