In this section
The Division of Laboratory Medicine (DLM) guidelines for specimen acceptance must be followed to ensure that all samples are correctly and unambiguously identified. The policy provides an overarching process to specimen rejection to help balance the requirement to process against the risk to patient safety. The EM specimen acceptance criteria below are in line with DLM policy. To ensure that specimens are linked to the correct patient, adequate identifiers are essential.
Electron microscopy samples must arrive at the laboratory in suitable sample containers and with relevant requesting information. These are detailed, respectively, in the section on packaging and below. Additionally, it must be established (either by prior arrangement or on the requesting paperwork) from which institution the sample has been referred, the requesting pathologist, where to send the results of the examination and by what means. Results will only be communicated back to the requesting pathologist or Histopathology department and not directly to Ward clinicians.
Our Specimen Acceptance Policy dictates that the following essential patient identifiers must be present as a minimum on both the requesting paperwork and the sample container:
- Family name
- First name
- Date of birth
- Sender’s reference number (e.g. laboratory number)
The following information must be provided on the specimen container and/or the requesting paperwork before the sample is processed since specific processing and/or embedding procedures may be required accordingly:
- The nature of the tissue (i.e. specimen type)
The following information is requested to be provided on requesting paperwork (or other means). If not provided, but all other acceptance criteria are met, the sample will be processed but may not be examined ultrastructurally until the information is provided.
- Clinical details and/or the specific rationale for EM examination. (This is particularly important for non-renal samples to allow a better ultrastructural examination to take place since expertise in ultrastructural pathology of the particular tissue type concerned will be limited. The examination may be delayed until this information is provided.)
The following information is requested to be provided on requesting paperwork (or other means) but, if absent, would not preclude sample acceptance, processing or examination provided that all other acceptance criteria are met.
- Full patient address
- NHS Number (if available)
- Number of pieces of tissue sent in the specimen container
A summary of specimen acceptance/requesting information criteria
| Information required | Requesting paperwork | Specimen container | Either | Requesting paperwork or by other means (eg, email to Lead BMS) |
| Family name | Yes | Yes | – | – |
| First name | Yes | Yes | – | – |
| Date of birth | Yes | Yes | – | – |
| Sender’s reference number (eg, lab number) | Yes | Yes | – | – |
| The nature of the tissue (ie. specimen type) | – | – | Yes | – |
| Clinical details and/or the specific rationale for EM | – | – | – | Yes |
| Notification marking the sample as urgent/priority | – | – | – | Yes |
| Patient address (preferable but not mandatory) | Yes | – | – | – |
| NHS number (preferable but not mandatory) | Yes | – | – | – |
| Number of tissue pieces sent in the specimen container (preferable but not mandatory) | – | – | Yes | – |
Multiple samples from the same patient
Different sample sites
If there are multiple samples from the same patient, sent as a single request (e.g. carrying the same senders’ laboratory accession number) and these samples are from different sample sites, tissue from each site must be in separate containers, each labelled in accordance with the above requirements. However, it becomes mandatory that the requesting paperwork must include a list of each sample which enables positive identification of its corresponding sample container (the use of corresponding numbering can be used if the same container is too small to fit the specimen type details on it).
Multiple samples, from identifiably different sample sites, sent as a single request will each be allocated the same MFT laboratory accession number. Each will also be given a unique alphabetic suffix starting from A. If the sender requires a particular suffix sequence for the return of the EM results, this must be communicated.
Same sample site
Multiple samples from the same patient, sent as a single request (e.g. carrying the same senders laboratory accession number) and from the same sample site (e.g. same kidney) should be sent in the same specimen container. If samples of this sort are sent in separate containers for a specific reason, this reason will need to be clarified before the samples are processed.
TopSpecimen ID discrepancy procedure
If any of the essential patient identifiers are missing from either the paperwork or the sample container, or there is a mismatch of information between them, the sender will be notified. Provided that three of the four essential identifiers are present and match-up, it will be sufficient for the sender to give the correct information over the telephone or via email. The sample will then be received into the laboratory and processed. However, if this condition is not met, the sample will be placed on hold and not accepted into the laboratory. The sender will be contacted for advice from the requesting pathologist as to whether the sample should be repackaged and returned for correction or whether there is a clinical need to receive into the EM laboratory and process it straight away. Please note that if the latter is the case then this advice must be received in an email from the requesting pathologist acknowledging the error and providing the correct information.
For any other discrepancy with respect to the specimen acceptance policy outlined above, verbal or email clarification will be sufficient.
TopSpecimen processing and preparation for examination
Tissue samples are each assessed for appropriate size, dissected (if necessary) and then processed into resin blocks.
Semi-thin sections are then cut from the blocks to identify those with suitable regions of interest. Those showing regions of interest are cut to produce ultra-thin sections which are subsequently mounted onto copper grids. Grids/sections are then stained ready for electron microscopy examination.
All material is then archived in accordance with current Royal College of Pathologists guidelines as a minimum.
TopSending previously processed tissue (wax blocks, EM blocks & EM grids)
These should be sent in the form in which they are created at the sending laboratory. They must be accompanied with requesting paperwork conforming to the specifications above.
External users forwarding FFPE material for EM must also provide precise information which allows localised extraction of the area of interest from the wax block. The following represents an order-of-preference list of ways in which this information can be obtained from the sender and which, ideally, would be provided along with the material itself.
- A light microscopy slide containing the section which best represents the tissue at the block face. The slide must be indelibly marked in a way to clearly indicate the area of interest.
- The area of interest is clearly marked on the block itself.
- Confirmation that the tissue remaining in the block can be dewaxed in its entirety (n.b. only be acceptable where there is not an unreasonably large amount of tissue in the block. See senior member of EM staff if necessary).
Senders sometimes prefer to determine an area of interest and extract it themselves, before sending. This is acceptable but not preferable to the above as it is often helpful to be able to assess the characteristics of the tissue macroscopically before any EM process begins.
Top(Last reviewed June 2025)