1.3 Transport, labelling and processing of samples
Specimens should be sent to the laboratory as quickly as possible so that the causative agent is still viable (able to replicate and divide) when it gets there, and is not overwhelmed by the growth of commensal organisms or contaminants. A variety of techniques are used to achieve this aim and to minimise the effects of any delay. Refrigeration and carefully designed transport media can keep the organisms viable for longer but add to costs.
Each sample should be uniquely labelled and registered in a database so that it can be attributed to a specific patient, and its analysis prioritised according to the urgency with which the result is required. It is important to make sure results are stored securely to protect the patient’s confidentiality.
Activity 4: Processing specimens in your workplace
Use the question prompts below to think how clinical specimens arriving in your laboratory are processed.
- How are samples recorded? Do you have an electronic system or database or are samples recorded in a book? What steps do you take to protect patient confidentiality?
- Is there anything that can be improved in your system?
Discussion
Things to consider are listed below; you may have thought of other points.
Patient confidentiality is important so that personal information in relation to the diagnosis including microbiology requests and results is kept safe – whether this is electronic or paper based. If the laboratory is small, it may be safer and easier to write the results in a book rather than setting up a database. For large numbers of specimens an electronic system is faster, but data must be kept secure and with safeguards in place to prevent data loss if the system crashes.
It is important to understand how the physicians will be using the results and work with them to make sure what you are giving them is useful to them. A close working relationship also helps them understand what the laboratory can and cannot do. Physicians need results as soon as possible to guide treatment. It is useful to monitor ‘turnaround times’ – how long it takes between receiving the specimen and issuing the results. Sometimes issuing interim results, such as the Gram stain result, may also be helpful.
Not all testing of isolates can be carried out in a hospital laboratory and specimens/cultures may need to be sent to a reference laboratory for further processing. For example, some organisms may be difficult to culture or may need more advanced techniques to identify to species level (see Section 3.3).
Activity 5: Preparing samples for transfer to a reference laboratory
What factors do you need to consider when sending isolates to a reference laboratory?
Discussion
Factors you may have considered are listed below; you may have thought of others.
- The basic growth requirements for most pathogens are catered for by culture on a nutrient, blood or a chocolate agar slope and stored at room temperature.
Fastidious organisms have specific requirements and may also need special transport conditions otherwise they may not survive the journey. It may not always be possible to send these.- Some isolates may require refrigeration or freezing, this may not be practical in your laboratory. Refrigerated transport may be required for such samples.
- If freezing of cultures is essential then it must be done properly, for example with beads and glycerol, so as not to kill the organisms. Once frozen, cultures should not be thawed until use as repeated freeze-thaw cycles lead to deterioration.
- Safe transport must be arranged for hazardous organisms or samples.
- It is important to consider how long cultures remain viable. It may be necessary to keep some in reserve and send batches for analysis.
Accurate labelling that ensures patient confidentiality is important. Generally, isolates are given a number that can then be cross-referenced back for full identification.
1.2 Impact of sample quality on testing and reporting of results
