Basic minimum standards acceptable for good laboratory practice is a sine qua non for the delivery of quality products, efficient services and cost efficiency. These are the core concerns of Quality Control in the Histopathology Laboratory.
According to the encyclopedia Britannica ‘A standard is that which has been selected as a model to which objects or actions may be compared’. It is a document that sets out a detailed description of requirements, dimensions, materials and /or procedures designed to ensure that a product or service meets its purpose and consistently performs to its intended use. It aims at achieving Consistency and Reproducibility.
The American Heritage English dictionary also defines quality as ‘an attribute of an individual or object’ seen as superiority of kind or as a level of excellence.
According to Wikipedia, quality ‘is the conformance to specifications’.
Divergent Views On Quality
Quality means different things to different professionals working in the histopathology laboratory, the patient and the requesting physician.
To the Medical Laboratory Scientist, quality means the production of high quality sections or slides. Probing questions considered include ‘is it well stained?’, ‘is it well differentiated?’ ‘Is it air bubble free; is it artifact free; are the required tissue elements specifically demonstrated?
To the pathologist, quality means accurate, timely and complete reports. To the requesting physician , quality means timely reports useful in the management of patients. To the patient, quality means getting timely medical treatment at the shortest possible time.
Therefore for the histopathology laboratory, quality control must be seen as the policies, practices and procedures enshrined for the production of high quality sections with accurate, timely and complete reports in a cost effective manner at all times.
Objectives Of Quality Control In Histopathology Laboratory
· To ensure quality services that guarantees patient’s satisfaction
· To produce high quality sections within and between laboratories
· To generate accurate, timely and complete reports
· To reduce turn around time
· To promote ethics and professionalism
· To enhance improved performance
· To enchance continuous training and professional development
Overview Of Quality Control
Quality Control in histopathology laboratory shall be considered in the following order:
· Pre-analytical requirements
· Analytical requirements
· Post-analytical requirments.
· Laboratory Design
· Request Form
· Laboratory Number
The laboratory must be designed to have enough space to accommodate all machines and tools, working benches, shelve for chemicals, retained slides and block storage. It must also support efficient and smooth workflow. It should have enough sink and the room should be well air conditioned.
There should be enough space to also accommodate specialized tests e.g. cytology, immunohistochemistry, histochemistry, archive room, tissue bank etc.
The room must be well ventilated with electrical wiring to standard laboratory specification.
Where there is challenge on power supply, alternative sources of emergency power supply must be made available for constant power supply.
Quality control cannot have a strong foundation without well trained, certified and competent medical laboratory professionals. Apart from being qualified and licensed, the personnel to handle medical laboratory diagnostic activities must continually enroll for continuous professional development courses to keep himself abreast of recent developments in his chosen field.
Professionals trained to partake in medical laboratory testing include, medical laboratory scientists, technicians and their subordinate staff.
No matter how competent and proficient a medical histoscientist may be, high quality sections cannot be guaranteed if obsolete, unserviceable and non-functional equipments are at his disposal. This precarious condition is still the lot of some third world countries’ histopathology laboratory.
Standard and modern microtomes, wax dispensers, staining machines, embedding work stations, cryostat, hot plate, oven, floating bath etc are vital for standard performance in the histopathology laboratory.
Sampling error is responsible for cases of insufficient and non-representative reports. This unnecessarily prolong treatment time and increase the cost of medicare at the expense of the patient and the expectant relatives.
Biopsies should be professionally taken with no error ( sufficient and at appropriate site) so that histopathological investigations could be satisfactorily completed with accurate reports.
Request form must be well customised to capture patient identity, requesting practitioner, test required, requesting facility/hospital, hospital number, clinical details, provisional diagnosis, information on drugs administered, date received, type of fixative, time of surgery and time of fixation to mention a few.
Fixation being the basis of histotechnological techniques must be perfectly done. Most laboratories still use 10% formol saline globally. For laboratories running immuno-services, 10% Neutral Buffered Formalin is recommended. Fixation should be done immediately after surgery and at worst, one hour post-surgery to arrest autolysis and putrefaction.
The volume of fixative should be 10-20 times the volume of the specimen i.e. ration of specimen to fixative should be ratio 1:10.
Large specimens like breast should be sliced open for the fixative to permeate it to avoid Ischaemic necrosis. In the same vein, lungs should be infused with formalin and covered with cotton wool soaked in formalin. The same treatment goes for the gastro-intestinal tract(intestine).
Bouin’s fluid is recommended for testicular biopsies. Immunohistochemistry specimens should be fixed for between 6 and 72 hours.
Fixed specimens should be transported in sealed, well labelled, sizeable plastic containers.
Samples received must be confirmed to have been properly fixed before acceptance in the laboratory. Once that is done, the patient’s information provided on the request form should be entered into the day register.
Laboratory identification number must be immediately assigned to registered samples which must be well labelled before being transferred to the grossing room.
Reagents must be original and stored in the right storage conditions at all times. They must be taken in adequate measurement, in the right container, well compounded, filtered if necessary and dated.
Deliquescent and hygroscopic chemicals should be stored in air-tight containers. Hydrogen peroxide should be stored in brown glass.
Schiff’s reagent should be stored in brown bottle and preserved in a refrigerator. Silver nitrate solution should be stored in a dark glass stoppered bottle and kept in a dark cupboard.
Information Communication Technology (ICT)
ICT infrastructures minimises error and greatly improves performance while at the same time reducing turn around time of histopathology services and reports. Electronic data entry, data capture, multimedia adaptation, electronic data storage and retrieval are means through which this is achieved.
The grossing room should be well ventilated with an air extractor. Other tools such as weighing balance, knives of different sizes, scissors, needle probles, thread, blade, ruler, board, sieve etc should be made available.
Brief description of the sample should be taken with reference to the size, shape, colour, nature and texture of the specimen.
All hard tissues should be sent for decalcification.
Processing of tissues should be fully automated. Right choice of reagents and processing schedule should be adopted. Periodic change of processing fluid is highly recommended depending on the workload of the laboratory.
Standard Operating Procedures
All methods and processes should be run with standard operating procedures following widely acceptable international standard such as name of author, title, principle, purpose, procedure, warning, harzards, precuations, date, supervisor, date to be reviewed and references.
Reagent control, positive controls and negative control for all the techniques.
Equipments should be kept warm through main power source for optimum performance. The paraffin waz oven should operated at required temperatures. Air conditioner should be switched on to maintain optimum performance and regulate excess heat generated by the machines. Refridgerators and freezers to be kept on to preserve reagents and arrest and arrest thawing and re-freezing. Finally, there should be periodic cleaning and lubrication of equipments.
Screening Of Slides
Slides must be adequately screened macroscopically and microscopically to ensure high quality before sent for reporting.
Laboratories must ensure documentation of all processes and procedures for effective service delivery.
Most laboratories especially in the third world countries still depend on microscopic reporting but multimedia imaging reporting is fast gaining ground in the developed world.
Speech recognition software has also replaced manual typing to eliminate errors and unncessary delay.
Adoption of standard criteria and reporting guidelines to reduce diagnostic fallibility such as oversight and misinterpretation is highly recommended.
Is the tissue malignant? Is it normal? If malignant what is the nature and origin of the tumour? How can it be graded and what grade does is fall? In order to have well acceptable reports, molecular grading (Immunohistochemistry) is highly recommended. Centers without immuno diagnostic facillities should link up with established centers for this service.
Typing Of Reports
Where manual typing is still in practice, it must be done by well trained, qualified and highly proficient typist who are well grounded in medico-pathology terminologies. In more advanced setting, speech recognition software is the best.
Communication on reports through clinico-pathology meetings with surgeons and physicians is highly recommended.
Peer review auditing using related samples would also be of immense importance. As a complement, specialist referal of difficult cases is of vital neccesity.
A laboratory audit is the process of comparing observations of actual conditions with requirements. Auditing processes, procedures, workflow output and turn around time should be done periodically to determine conformance with established policies, procedures and processes.
Dispatch of Reports
Rapid dispatch of reports to requesting clinicians is highly recommended and duplicates should be kept in the laboratory.
Electronic dispatch of reports will be of great benefit where information technology infrastructures are installed.
A well ventilated, fully air conditioned archive room should be set aside for blocks of tissues handled in the histopathology laboratory. A systematic method of indenting and filing should also be put in place for easy retrieval of the blocks in the future.
Filing cabinets musth be made of steel and not wood. This is necessary to insulate the blocks from destructive fire incidents that may occur.
Special cases and positive blocks should be kept in a fully air conditioned, well refrigerated apartment. This will promote research and educational advancement.
Seminars And Continuous Professional Development
This should be seen as a complementary and important aspect of quality control in the histopathology laboratory. Quality control efforts will succeed where the personnel are well exposed and abreast of current trends.
Before any testing is done in any laboratory or before new process can beging, the laboratory needs to identify and purchase all related materials and reagents. Inventory of laboratory consumables, reagents and equipments. Suppliers should have identification seals for items supplied.
Critical Value Reporting
Critical value reporting captures and analyses non-conforming events contrary to established policies, procedures and practices ain the laboratory. It is a means of identifying occurrences, remedial action taken, investigation and documentation done, action plan, classification of the occurrence , analysis and presentation, management review and follow up.
Quality Assurance Program
Quality assurance measures current performance, compares it with established goals and good laboratory practice and is eventually aimed at improving services.
A standard histopathology laboratory must have both internal and external quality assurance policies.
Laboratory Information System
A laboratory information system stores information in a relational database, such as Oracle, DB2 or MS SQL. A link is established between samples, storage conditions, test dates, analyst certification, instrument calibration and testing parameters. It is aimed at supporting automation in the laboratory, reducing turn around time, improving service quality, and reducing errors.
In conclusion, quality control is essential for effective performance of the laboratory. However, it is instructive to note that it can only thrive in a conducive setting.
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• Institute of Applied Sciences, Analytical Laboratory Standard Operating Procedures.
• Requirements for Pathology Laboratories (2007 edition): Autralian National Pathology Accreditation Advisory Council
• Guidelines for the Implementation of a National QA Programme in Histopathology: Faculty of Pathology, Royal College of Physicians of Ireland
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• R. R. Nakhleh, What is quality in surgical pathology? J Clin Pathol July, 2006; 59(7): 669-672
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• John D. Bancroft, Marilyn Gamble,Theory And Practice of Histological Techniques: Fifth edition, Churchill Livingstone