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Ch 8.Immunohistoch / immunology
Ch 10.GC/MS, NMR and Proteomics
Bone biopsies are usually decalcified for a period ranging from one hour to days in a weak hydrochloric acid solution or in EDTA. With the aid of microwave exposure, the time is accelerated from one hour using conventional methods to as little as 10 minutes for bone marrow core biopsies using formic acid.
Treatment time depends on thickness and on density: solid bone and teeth take more time than spongy bone. Bone marrow biopsies require as little as 10 minutes exposure time.
Standard fixation protocols in formalin take a minimum of four hours at room temperature. Fixation aided by microwave exposure and pre- and post-treatment in formalin take less than 30 minutes.
10% NB Formalin can virtually be eliminated from the laboratory. Immunostaining is greatly enhanced in microwave-fixed tissue. Time is saved versus conventional 4 hour fixation .
Many laboratories are generally resistant to changes in established procedures. No control of time in formalin when specimens are received from outside the lab. Immunostaining results may vary due to changing times in formalin and increased cross-linking.
Many factors must be considered when thinking about switching to microwave fixation of tissue rather than conventional fixation. First, the manner in which specimens are transported to your laboratory is the most critical factor in controlling pre-fixation time in formalin. Any reference laboratory or laboratory receiving specimens through the mail generally receive these specimens already fixed. These laboratories can consider removing formalin from the tissue processor and storing specimens in 70% Ethanol for a more chemically-friendly laboratory.
The laboratories which process samples biopsied at their own medical center or picked up by a local courier can best utilize microwave fixation. These labs can control times in formalin pre-fixation, which can lead to more consistent immuno results.
Another factor to be considered is the change in scheduling in the standard laboratory routine. Scheduling changes will affect everyone, from the courier to the clerical people involved in reporting.
I conclude that microwave fixation is not adaptable to every laboratory, but, in those situations where specimen transport can be regulated, it can be both cost-effective and more healthy for technicians and the environment. Keep in mind that any laboratory can utilize this time-saving procedure for stat biopsies, which can ultimately contribute to better patient care and a good option for fast specimen turn-around.
Slide drying in a conventional oven is done at temperatures between 60C and 80C, for times ranging from 20 to 60 minutes. Slide drying in a microwave takes from 2 to 5 minutes.
Equipment: Laboratory microwave with output power from 600-900 watts and equipped with a carousel. Microwave-safe slide racks holding 20-24 slides
Note: Times will vary with output power of microwave, and must be determined experimentally in each laboratory with its microwave
Note: When consequetive batches are dried in a microwave, the microwave cavity temperature will get gradually higher. When not drying slides, keep cavity door open to allow for cooling between batches.
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Reagent |
Procedure |
Volume |
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Tech Initials |
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100% Ethanol |
15 min x65C |
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Propanol |
10 min x74C |
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Paraffin |
5 min x65C |
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Paraffin |
min x74C |
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Paraffin |
5 min x82C** |
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