Use of the Laboratory and Collection of Specimens PDF

Use of the Laboratory and Collection of Specimens Putting what you have learned into practice  Laboratory Functions: Diagnostic Detection of infectious agents – guidelines for treatment – information for individual cases – collated information for general use (e.g...

Use of the Laboratory and Collection of Specimens Putting what you have learned into practice  Laboratory Functions: Diagnostic Detection of infectious agents – guidelines for treatment – information for individual cases – collated information for general use (e.g. antimicrobial susceptibility summaries)  Epidemiological Information provided can be used to complement clinical information – Track resistant isolates (e.g. MRSA) – Follow trends in development of resistance – Detect or confirm outbreaks related to infectious agents – Support control efforts, Public Health support  Making the best use of the lab Lab results correspond to the initial clinical question Decreased frustration – for patients and health care workers Most cost effective use of Lab resources Speediest results by eliminating delays  More Advantages of being a Smart Laboratory User By providing information, specialized testing can be accessed for unusual circumstances Avoidance of liability of mislabelled specimens, or loss of specimens. General Principles of Specimen Collection Send as good quality specimens as possible, avoiding contamination with normal flora as much as possible. Make sure both specimen and requisition are labeled with patient name, birth date and health number, specimen type, etc. Put relevant clinical information on the requisition.  Getting the Best Results Maximize Sample Quality Use the appropriate transport media. Get specimens to the laboratory rapidly When in doubt – ask the laboratory (especially if a request is unusual or needs additional testing, or results are unclear, etc.) When problems arise, work with laboratory staff to fix them. Specimen Collection – General Considerations Issues to consider when collecting specimens: – Whether the specimen will provide useful information. – Choice of the type of specimen – Instructions for collection by patient – Need for transport media – Time taken for the specimen to get to the laboratory  Specimen Collection - General Considerations (cont’d) – Quality of the specimen – Risk of false positive (↑ if specificity is low) or false negative results (↑ if sensitivity is low) – How to interpret the results. (predictive values) Each hospital/lab may provide detailed instructions for specimen collection. The following is a guide for collection of good quality specimens, but deals only with the most commonly collected specimens, or types of specimen.  Guidance in Nova Scotia http://www.cdha.nshealth.ca/pathology- laboratory-medicine/microbiology- services-diagnostic PROVINCIAL MICROBIOLOGY USERS MANUAL on website at bottom of page  Specimen Collection - Urinary Tract Specimens: – Mid stream urine – In-out catheter urine – Indwelling catheter urine  Urine – Patient Instructions Patient instructions: Mid Stream Urine: – Decrease skin contamination by parting labia, retracting foreskin. – Cleansing the urethral opening is no longer recommended by the American Society for Microbiology. – After passing a few milliliters collect the specimen in a clean sterile container.  Urine Specimens – Transport medium is not required if urine is transported to the lab within 2 hours or refrigerated at 4C and delivered within 24 hours. Preservatives can be used if delivery to a lab is likely to be delayed, or transport prolonged. – Label the container with the patient name, another identifier and specimen type. DO NOT DO NOT collect urine from bedpans, SAMPLE!! urinals, or catheter bags  Urinary Catheters In/Out Catheters: – Use aseptic technique to introduce the catheter. – Discard the first few ml of urine that pass. – Collect the specimen and submit it as above. Indwelling Catheter: – Collect the specimen using a needle and syringe after cleaning the collection site with alcohol, and send as above.  Respiratory Tract Specimens Specimen Types: – sputum – induced sputum – tracheal aspirate  If TB is suspected, use precautions to prevent spreading infection.  Don’t have TB patients cough in your face(or in your room)  Sputum Patient instructions: Decrease contamination by saliva by removing dentures, cleaning teeth (no toothpaste – as the residue may be antibacterial), gargling and rinsing mouth with sterile water (not tap water - may be contaminated with Legionella or pseudomonas). Avoid collecting post nasal discharge. Deep cough from the chest  Sputum Collection Collect sputum in a dry sterile container Transport to the laboratory as soon as possible but at least within 24 hours. Refrigerate at 4C if there is delay in delivery. Degree of contamination with saliva can be detected in the lab by microscopy, by identification of squamous cells.  Other Respiratory Specimens Induced Sputum: – Induction of sputum using saline aerosols can be useful if patient cannot produce sputum. – Sputum produced after bronchoscopy is a good specimen also. – Collect and transport as above. Tracheal Aspirate: – Useful in intubated patients. – Specimen collection traps are prone to leaking during transport.  Enteric Specimens Specimen Types: – Stool Patient Instructions: Stool: – Pass stool on clean dry surface (e.g. paper) If liquid into a clean container – Place an almond sized portion in the specimen container  Stool Transport Media – For Culture use Enteric (Cary Blair) Transport medium – For parasites use SAF parasite preservative – For cytotoxicity and virology testing use a dry sterile container – Transport to lab as soon as possible or refrigerate at 4C (no more than 24hrs) – Send stool rather than rectal swabs if possible  Swabs Choice of specimens: – throat – wounds – urethra, etc. Not for abscesses, Fluids, TB culture  Using Swabs Instructions: – Use a swab only if there is insufficient quantity to collect in a syringe and send in a dry sterile container. Some material will be absorbed by the swab. – Collect purulent material. – Avoid contamination with surrounding normal flora on skin etc.  Transport of Swabs – Use an appropriate transport medium to increase organism survival or for specific organisms (e.g. Neisseria gonorrhoeae culture, viruses, chlamydia). – Some instruments (for example for Chlamydia/N. gonorrhoeae) use specific swabs – Avoid dry swabs for sending specimens. – If available, anaerobic swabs are 20X the cost of aerobic swabs, and so should be used judiciously (e.g. on deep infected wounds but not on mucous membranes).  Biopsies, Sterile Fluids Specimens: – tissue – pleural fluid – pericardial fluid – CSF – vitreous fluid, etc.  Collection of Biopsies, Sterile Fluids Instructions: NO FORMALIN!! – Collect in a dry sterile container and send to the lab without delay. – Labelling must be complete and correct. – It is not necessary to add sterile water to biopsies unless they are very small and in danger of drying out. Just add a few drops to maintain humidity – Microbiology specimens should never be put in formalin (it kills all the bacteria).  Results Microscopy is usually available within 1 - 2 hours of specimen receipt for stat samples. Cultures may take from overnight to several weeks for some organisms (e.g. TB). Most are available within 3-5 days. Rapid testing (e.g. antigen detection) may be available on a same day basis. Susceptibility results usually require a further overnight incubation.