One of the most important steps to ensuring consistent and trouble-free tissue processing is reagent maintenance. Keeping reagents fresh is critical to proper tissue processing and overall quality control (QC). Since over-used reagents lead to problems that are difficult to diagnose, most laboratories keep a maintenance log to keep track of how often reagents are changed and rotated. Determining how often each reagent is changed is as individual as the processing protocol for every laboratory. Some laboratories implement reagent changes based on how often each reagent is used. Other laboratories change reagents based on the number of cassettes or the amount of tissue processed, rather than a rigid calendar schedule. Once determined, reagent maintenance schedules should be adhered and charts should be utilized for tracking purposes, in order to retain consistent quality of processed tissue.
Another important QC check is the paraffin temperature. As mentioned earlier in this course, melted paraffin must be kept at 2-4° C above the melting point of paraffin. The paraffin chambers on the processor must maintain the proper temperature and this temperature should be checked daily. Paraffin may also be melted and stored in special paraffin pots so that melted paraffin is always available for filling the embedding center or the processor. The paraffin pots must be temperature controlled and monitored daily for the proper temperature. If the paraffin is cooked at high temperatures it will breakdown and cause microtomy problems. Since there are dozens of paraffins available on the market, technical support from the processor manufacturer is recommended. Not all paraffins are made for all processors or all applications.