histo lesson 6
Specimen Collection Guidelines
Importance of Proper Specimen Collection
The proper collection of a specimen for culture is the most crucial step in recovering pathogenic organisms responsible for infectious disease.
A poorly collected specimen may lead to:
Failure in isolating the causative organism(s).
Recovery of contaminating organisms.
Basic Concepts for Specimen Collection
Collection Site:
Collect the specimen from the actual site of infection.
Avoid contamination from adjacent tissues or secretions.
Decontamination of Skin Surface:
If appropriate, decontaminate the skin surface using:
70-95% Alcohol (ALC)
2% Chlorhexidine
1-2% Tincture of iodine
Allow a contact time of two minutes to maximize the antiseptic effect.
Timing of Collection:
Collect specimens at optimal times (e.g., early morning sputum for AFB culture).
Material Quantity:
Collect enough material for accurate testing.
Collection Devices:
Use appropriate, sterile, leak-proof specimen containers.
Transport Media:
Use specific transport media based on specimen type:
Anaerobe transport vials for anaerobic cultures.
Amies or Stuart transport swabs for bacterial culture.
Cary-Blair for stool culture.
Virus Transport Medium for viral cultures and Chlamydia cultures.
Expiration Check:
Check the expiration date before inoculating the collection device.
Antimicrobial Considerations:
Whenever possible, collect specimens prior to administering antimicrobials.
Labelling and Requisition Completion:
Proper labeling of the specimen is required, including:
Specific source of specimen (e.g., wound, left leg).
Complete the test request form accurately.
Minimizing Transport Time:
Ensure prompt transport of specimens to maintain integrity.
Transport Environment:
Maintain an appropriate environment between collection of specimens and delivery to the laboratory.
Outcomes of Correct Specimen Collection
Following basic specimen collection concepts results in:
Lab results that correspond to the initial clinical question.
Decreased frustration for patients and healthcare workers.
Most cost-effective use of laboratory resources.
Quickest results by eliminating delays.
Access to specialized testing for unusual circumstances.
Avoidance of liability related to mislabeled specimens or loss of specimens.
Considerations for Collecting Specimens
Consider the following when collecting specimens:
Will the specimen provide useful information?
What type of specimen to collect?
Instructions for collection by the patient.
Need for transport media.
Time taken for the specimen to reach the laboratory.
Quality of the specimen.
Risks of false positive or false negative results.
Interpretation of results.
Each laboratory provides detailed instructions for specimen collection. These must be accessible via a Specimen Collection Manual/Guide for all healthcare staff.
Timing and Handling of Samples
Samples must reach the laboratory as soon as possible after collection:
To prevent overgrowth of normal bacteria.
To prevent die-off of pathogenic organisms (e.g., Neisseria gonorrhea, Neisseria meningitis).
To prevent the deterioration of toxins for detection tests (e.g., Clostridium difficile).
Specific Transport Guidelines:
CSF, blood cultures, and swabs for isolation of Neisseria gonorrhea must not be refrigerated.
Urine and sputum samples must be refrigerated if there is a delay in transport.
Specimen Collection Manual Overview
The specimen collection manual provides clear guidelines and instructions for personnel responsible for specimen collection and handling:
Covers policies and procedures for proper specimen collection and handling.
Includes client/patient interaction guidelines.
Contents of the Specimen Collection Manual
Collection Instructions:
Detailed instructions for collecting various specimens (blood, feces, sputum, cytology, tissue, urine, etc.)
Description of Collection Containers:
Information on containers used and necessary additives.
Volume and Preparation Instructions:
Instructions for the type and amount of specimen to be collected.
Blood collection instructions must indicate:
Volume of blood per anticoagulant in the tube (ratio).
Patient Preparation:
Instructions for preparation of the patient prior to collection.
Special Timing Instructions:
Guidelines for the timing of specimen collection.
Clinical Information Requirements:
Specify clinical information needs when required (e.g., travel history).
Patient Handout Instructions:
Instructions in English and French for self-collection of samples (e.g., urine, sputum, feces).
Positive Identification of Patient:
Instructions for positive identification before specimen collection.
Collector Identification:
Record the identity of the person performing the sample collection.
Consent Requirements:
Instructions on needing patient consent prior to collection.
Completing Requisitions:
Guidance on completing various requisition forms.
Sample Collection Requests:
Who may request sample collection for testing.
Turnaround Time for Test Results:
Information on expected turnaround times for test results.
Referral Instructions:
If laboratories refer samples to another hospital laboratory for testing, instruction details should be provided for the referral site.
Availability of Online Guides:
Many hospitals/community laboratories/Public Health Laboratories have their Specimen Collection Guides posted online.
Sample Labelling Requirements
Every specimen must be labeled with:
Patient’s full name (or unique code number for anonymous testing).
One additional unique identifier (e.g., MRN number, health card number).
Date of collection.
Time of collection.
Initials or Health Information System mnemonic of the person collecting the sample.
Urine Specimens for Bacterial Culture and Sensitivity
Specimen Types
Mid-stream urine
In-out catheter urine
Indwelling catheter urine
Patient Instructions for Mid-Stream Urine
Cleanse the urethral opening using soapy water, rinse with sterile water or cleansing wipes.
After passing a few milliliters into the toilet, collect the specimen in a clean sterile container.
Transport medium is unnecessary if urine is delivered within 2 hours or refrigerated at 4°C within 24 hours.
Preservatives may be used if delivery is likely to be delayed.
Label the container with patient’s full name, date of birth, date & time collected, and specimen type.
Avoid collecting urine from bedpans, urinals, catheter bags, or diapers.
Basics of Specimen Collection and Handling of Urine Testing
Classification of Urine Specimens
Urine specimens are classified by:
Type of collection conducted.
Collection procedure used.
Random Specimen
A common specimen for analysis, easy to obtain.
Usually submitted for urinalysis and microscopic analysis but not the preferred specimen for either test.
Can give inaccurate health views if too diluted, affecting analyte values.
Can be collected at any time; instructions should prevent contamination during collection.
Midstream Clean Catch Specimen
Preferred for bacterial culture and sensitivity testing due to reduced contamination incidence.
Patients must first cleanse the urethral area with a castile soap towelette, void initial urine portion, and collect midstream urine.
Catheter Collection Specimen
Conducted for bedridden patients or those unable to urinate independently:
A foley catheter is inserted to collect urine specimens.
Collection can also occur through an existing catheter, directly into an evacuated tube or via syringe.
Suprapubic Aspiration Specimen
Used when catheterization is impossible or when a sterile specimen is required:
Collected via needle aspiration through the abdominal wall into the bladder.
Pediatric Specimen
For infants and small children, urine is collected using a specialized bag adhered to the skin around the urethra.
Post-collection, urine is transferred to a collection cup or evacuated tube; urine from a diaper is unsuitable due to contamination from materials.
Respiratory (Sputum) Specimens for Bacterial Culture and Sensitivity
Specimen Types
Sputum/Induced Sputum
Tracheal Aspirates
Sputum Collection Instructions
Collect a first morning specimen before eating.
Minimize saliva contamination by:
Removing dentures.
Cleaning teeth without toothpaste.
Gargling and rinsing with sterile water.
Avoid collecting post-nasal discharge.
Obtain deep cough from the chest and collect sputum in a sterile container.
Transport to the laboratory as swiftly as possible, ideally within 24 hours; refrigerate if there is a delay.
Lab will assess contamination level through microscopy, identifying squamous cells.
Rejection Criteria for Sputum:
If there are greater than or equal to 10 squamous epithelial cells per low power field, the specimen will not be tested.
Stool Specimens for Culture and Sensitivity
Specimen Types
C. difficile Kit
Ova & Parasite Kit
Cary-Blair for Stool Culture
Patient Instructions for Stool Collection
Pass stool on a clean dry surface (collection Hat).
Place an almond-sized portion in the specimen container; avoid overfilling.
For culture use Cary-Blair medium and mix the sample well.
For parasite testing, SAF preservative is used and the sample must be mixed well.
For C. difficile and virology testing, use a dry sterile container.
Transport specimens to the lab promptly, ideally within 24 hours; collect stool instead of rectal swabs whenever possible.
Swab Specimens for Culture and Sensitivity
Specimen Types
Throat
Eye
Ear
Wounds
Genital
Skin
Hair
Nails
Collection Instructions for Swabs
Collect purulent material while avoiding contamination from surrounding normal flora.
Use an appropriate transport medium based on the specific organism.
Avoid dry swabs for sending specimens; anaerobic swabs should be used judiciously due to their higher costs.
Aim to transport specimens to the laboratory as soon as possible, ideally within 24 hours.
Specific Swab Details
Swabs with Transport Media:
Amies Charcoal Swab
Virus Transport Media
Nasopharyngeal swabs - fine and tiny.
Nasopharyngeal Swab Instructions
In some laboratories, throat swabs may be collected by Medical Laboratory Assistant/Technologist.
Instructions for Throat Swab:
Use Amies Charcoal Swab.
Have the patient open their mouth wide.
Depress the tongue with a tongue depressor before gently swabbing the mucosa behind the uvula and between the tonsils.
Recent Adaptations for NPS Swabs
Since the onset of the Covid-19 pandemic, healthcare workers have been trained to collect nasopharyngeal swabs.
These are used for diagnosing viral respiratory infections and pertussis (whooping cough), and should ideally be collected shortly after symptom onset.
Sterile Specimens for Culture and Sensitivity
Specimen Types
Tissue
Pleural fluid
Pericardial fluid
CSF (Cerebrospinal Fluid)
Blood
Vitreous fluid, etc.
Physician Instructions for Collection
Collect sterile specimens in a dry container and send to the lab without delay:
CSF and other fluids require STAT processing.
Ensure labeling is complete and accurate.
Sterile water is not necessary for biopsies unless they are small and at risk of drying out.
Laboratory Processing Timelines
Microscopic results typically available within 1-2 hours of specimen receipt.
Culture results may take from overnight up to several weeks for specific organisms (e.g., TB); most are available within 3 days.
Rapid testing (e.g., antigen detection) may provide same-day results.
Susceptibility results usually require additional overnight incubation for accurate analysis.