Parasitology Specimen Collection Overview

Specimen Collection, Transport, Preservation, and Processing

• Diagnosis of parasitic infections involves identifying parasites or their components and detecting host immune responses.
• Stool is the most common specimen for examination, but other specimens like urine, blood, CSF, sputum, and tissue samples may also be used.
• Stool specimens should be collected in clean, wide-mouthed containers with tight-fitting lids.
• For parasitic infections, stool samples should be taken every other day for 10 days, or 6 specimens within 14 days for amoebiasis
• Samples should include patient name, age, gender, date and time of collection, requested physician, procedure, presumptive diagnosis, prior infections, and travel history.

Factors to Consider for Stool Exam

• Patient's drug/medication intake (e.g., antacids, anti-diarrheals, antibiotics, antimalarials) should be noted.
• Contamination with toilet water, urine, and soil should be avoided.
• The age of stool samples affects the examination results.
• Delays in examination necessitate preservation methods.
• Stool samples should be stored at 3-5°C (refrigerator) and never frozen.

Stool Preservation

• Preservatives (e.g., formalin) prevent helminth egg and larva destruction and preserve protozoan morphology.
• The ratio of stool to preservative is 1:3.

Formalin

• Formalin, in 5% and 10% concentrations, is a common fixative.
• 5% formalin is used for protozoan cysts; 10% formalin is used for helminth eggs and larvae.

Schaudinn's Solution

• Used to preserve fresh stool for staining smears.
• Contains Mercuric Chloride (toxic).

Merthiolate-Iodine Formalin

• Contains Merthiolate/iodine solutions that stain and preserve protozoans.

Polyvinyl Alcohol

• Adheres stool to slides and preserves protozoan cysts/trophozoites for staining.

Sodium Acetate-Acetic Acid Formalin

• A liquid fixative with long shelf-life that does not contain Mercuric chloride.

Macroscopic Examination

• This involves examining the stool's color and consistency.
• Stool consistency can be liquid/soft or formed, which indicates trophozoites or cysts, respectively.
• Different stool colors correspond to different GI bleeding locations.

Microscopic Examination

• White blood cells (WBCs), red blood cells (RBCs), macrophages, Charcot-Leyden crystals, and arthropods eggs are examined.
• Parasites are identified through microscopic examination.

Parasitic Techniques

• Direct fecal smear (unstained and iodine-stained): Detects trophic forms of amoeba and flagellates.
• Kato thick smear: Detects eggs with thick shells, useful for mass stool examinations.
• Concentration Techniques (e.g., sedimentation, flotation): Recover cysts, oocysts, helminth eggs, and larvae.
  • Sedimentation: Based on differences in specific gravity
  • Flotation: Based on differences in specific gravity.
• Culture Methods: Used for hookworms, Strongyloides, and Trichostrongylus spp.; also for intestinal protozoans; Copro and Harada Mori.
• Egg Counting Procedures: Assess the severity of disease and worm burden.
• Permanent Stains: Identify intestinal protozoans (e.g., B. coli, G. intestinalis).

Other Specimens and Techniques

• Other specimens include blood, CSF, tissue aspirates/biopsies, sputum, and genital secretions.
• Methods to examine such specimens also include thick and thin smears, knott's concentration, and serological testing.

Quality Assurance in the Parasitological Laboratory

• A system for continuous improvement in the reliability, efficiency, and utilization of laboratory services.
• Internal Quality Control (IQC): Internal process review.
• External Quality Assessment (EQA) assessment by an outside party.
  • Includes proficiency testing, rechecking/retesting, and on-site evaluations.
• Components include laboratory personnel proficiency, standardized techniques, correct sample collection/processing, proper results analysis, and accurate report writing.
• Quality Assessment Program (QAP): a clinical laboratory requirement for license renewal, including Internal and External Quality Assessment.

Procedure Manual

• Includes instructions for proper specimen collection, reagent/solution preparation, techniques, quality control, reporting, and safety precautions.
• Necessary equipment (e.g., microscope, centrifuge, incubators) and reagents (e.g., stains, fixatives) are also mentioned.

Proper Use of Microscopes

• Understand microscopy parts (head, base, arm, eyepiece, eyepiece tube, objective lens, nose piece, stage, stage clips, aperture, adjustment knobs, microscopic illuminator, condenser, diaphragm) and their functions.
• Instructions for daily microscope maintenance are included (e.g., checking for damage, cleaning, covering).