The method of processing tissue for histological examination has remained largely unchanged for many years. Tissue processing introduces an enforced ‘delay’ in the specimen pathway during which little can be done to the specimen to speed diagnosis. Attempts have been made to improve the process (eg microwave assisted, xylene-free processors) or develop a more open system (eg continuous flow, multi-retort processors) but to date these techniques have introduced changes elsewhere in the specimen pathway, requiring redesign of either the cut-up techniques or alteration to subsequent methodologies in areas such as immunohistochemistry.
Ultrasonic vibration
The Jokoh Histra-QS ultrarapid tissue processor, available from Launch Diagnostics and evaluated in the present study, is recognisable to most biomedical scientists in histopathology as it both looks and acts like a conventional tissue processor. However, specimens up to 200 mm2 (10x2x2 mm or 5x4x2 mm) can be processed within one hour without prior formalin fixation. The processor uses xylene, graded alcohols and wax, which are pumped sequentially into a retort chamber. This chamber is then subjected to periods of ultrasonic vibration during the course of the processing cycle. Processing runs can be varied from 38 minutes upwards, depending on tissue size. Over a 12-month period, this study found the most effective cycle to be 58 minutes, which allowed a full load (20 cassettes) of mixed tissue types and sizes to be processed.
This rapidly processed tissue does not require specialised dissection techniques and from trials appears to have no detrimental effect on any subsequent laboratory techniques. Indeed, some studies have shown that preservation of certain tissue elements (eg RNA) may even be enhanced using this technique. The similarity with conventional processors means that little or no additional training is required to operate the processor (using a simple touchscreen) and also maintain reagents (the requirement for fluid exchange as with conventional tissue processors).
Mophology and management
On examination, tissue morphology is unchanged by ultrasound-mediated processing, even when starting from fresh tissue. In a blind comparative trial of gastrointestinal biopsies undertaken at Queen Elizabeth Hospital, Woolwich, there was 99% concordance in the histopathologists’ diagnoses between conventional and ultrasound-mediated processed tissue.
Routine biopsy diagnosis can be driven towards a continuous flow system as the turnaround time for manageable batches of work lends itself to increased flexibility during the working day. Consequently, the management of biopsy specimens is far more accommodating of the continuous arrival of specimens to a laboratory throughout the working day, especially for those with clinical urgency.
Turnaround time
The introduction of this capability to a department can have a dramatic impact on turnaround times for biopsy specimens, reducing conventional three-hour or overnight processing to less than an hour. In addition, it eliminates the need for a ‘fixation’ period, and the instrument is ready to be rerun after a 15-minute clean cycle. This will have significant impact on, for example, breast core biopsies as current guidelines recommend six to eight hours in formalin prior to processing to ensure optimal preservation of hormone receptors. Comparative studies show that oestrogen receptor (ER), progesterone receptor (PR) and HER2 presentation is not compromised when processing fresh tissue aided by ultrasonic technology. The potential can therefore be realised for not just same-day haematoxylin and eosin (H&E)-stained biopsy reporting but also same-day immunohistochemistry reports.
One aspect of service delivery is urgent biopsies (eg renal biopsies) where around 11% are inadequate and require repeat biopsy. This often results in an overnight stay and re-biopsy the following day, incurring the need for additional bed space and an associated cost to the Trust. Using this rapid biopsy processor, turnaround times can be reduced by 50%, allowing time for re-biopsy as a day case and earlier patient discharge.
Ultimate benefit
Staining of ultrasound-mediated processed tissue yields results comparable to conventionally processed tissue. These tests were carried out and validated at two independent diagnostic centres (Queen Elizabeth Hospital, Woolwich, and Barts and the London NHS Trust). In each case standard protocols for special stains and immunohistochemistry worked well without adaptation.
The Histra-QS ultrarapid tissue processor can be used positively to affect the turnaround time of biopsy specimens for histological diagnosis. Increased speed, flexibility and adaptability of the system will allow laboratories to manage specimen flow in a more efficient and timely fashion in order to meet ever-increasing deadlines of national targets, clinical urgency, local multidisciplinary meetings and consultant histopathologist requirements, and ultimately will be to the benefit of the patient.
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