Handling Hazardous Chemical Waste

Introduction

The US Environmental Protection Agency (EPA) defines waste as any solid, liquid or contained gas that is no longer used and is designated for disposal or recycling.  If the waste can cause injury or death, or pollute land, water or air, it is deemed to be hazardous.  The EPA regulates hazardous waste at the federal level, and state regulation must be at least as stringent as the EPA.

In 1976, the Resource Conservation and Recovery Act (RCRA) was passed to track hazardous chemicals “from the cradle to the grave”.  RCRA defines two categories of hazardous waste:

  • Listed waste is any substance appearing on any one of RCRA’s four lists.
  • Characteristic waste is any substance having one or more of the following characteristics:
  • This includes liquids with a flash point of less than 140 F (i.e. nearly all clearing agents and dehydrants/alcohols).
  • This includes liquids with a pH less than or equal to 2.0, or greater than or equal to 12.5.
  • Substances that are unstable or undergo violent chemical reaction with water or other materials (i.e. picric acid).
  • TCLP toxicity. Substances that can leach from a secure landfill.

Strategies for Waste Handling

Recycling

Recycling makes the most sense.  Alcohols, xylenes, xylene substitutes and formalin are examples of chemicals found in the histology laboratory that can be recycled.  The laboratory can keep smaller quantities on site and recycling is very cost effective.  Most recycling units pay for themselves in approximately two years.

Scaling Down

Try to “scale down” the quantities of chemicals that you use.  For example, if you are performing an iron stain on two slides (i.e. patient and control) instead of using 50 ml in a Coplin jar, use 10 ml in a plastic slide holder.  This decreases the amount of hazardous chemical waste you generate for this stain by more than half.

Re-use or “treat and release”

Non-mercury Harris’ hematoxylin is an excellent candidate to be re-constituted and re-used after the first use. Then, once it is depleted, hematoxylin can be treated for drain disposal (with permission from the owner of your sanitary sewer).

Store for legal transport and disposal

This is the method of last resort.  Alcohol tainted with xylene and special stains fall into this category.  These chemicals should be stored safely in drums for legal pick up and disposal by a licensed facility.  Remember, even after the facility comes to pick up your waste – you still own it.  If the waste hauler flips his truck over on the interstate, and your waste is on board – your laboratory helps pay for the clean up.  If you are found negligent in handling your hazardous waste, there can be criminal charges, and you – yes you – can go to jail.

Substituting for Hazardous Chemicals

Introduction

One strategy for decreasing the laboratory use of hazardous chemicals is to find substitutes for them.  Ideally, a “safe” substitute is the best alternative.  However, a “less hazardous” chemical also can help in this regard.

Processing

Fixation.  Formaldehyde (i.e. formalin) has been the fixative of choice in histology laboratories for many years.  However, you can see from the Formaldehyde Standard that many parameters must be met to insure employee safety when handling formalin.  Spent formalin is a hazardous waste; however, it can be recycled.

Today, many formalin substitutes are available for fixation of tissue.  One must be aware, however, that many of these substitutes are alcohol based.  Formalin is a cross-linking fixative.  Alcohol fixes tissue by denaturation.  It is important to work with your pathologist to validate any changes in processing chemicals that are made, to ensure that the final slide is acceptable.

Dehydration.  Dehydration of tissues during processing is still carried out by a graded alcohol series.  Laboratories usually employ ethanol for this procedure.

Clearing.  Xylene has been the clearing agent employed by laboratories for many years.  It is like formalin in that proper ventilation must be used when handling it.  Xylene is also easy to recycle.

Also like formalin, there are many xylene substitutes available for use.  Some are limonene based (i.e. citrus based).  These are considered safe, however there are some reports indicating that some personnel may be allergic to them.  Additionally, there are xylene substitutes that are short-chain and long-chain aliphatic hydrocarbons.  Whatever substitute is chosen, the laboratory should make certain to perform validations to insure specimen integrity.  Additionally, all xylene substitutes can be recycled.

The most important aspect of using xylene substitutes (whether in processing or staining) is that they all are very water intolerant.  Xylene can dissolve up to 3% water with no deleterious effect on processing or staining.  Tissues and slides must be completely dehydrated prior to the xylene substitute stations on the tissue processor and stainer to insure optimum quality.  This requires a strict regimen of changing and rotating the 100% alcohols that precede the clearing step.

Incorporating some of these ideas may be time consuming, however, they will make your laboratory a safer place to work.

REFERENCES:

  1. Theory and Practice of Histological Techniques. JD Bancroft, A Stevens ed.  Churchill   Livingstone, NY.  Fourth edition. 1996
  2. Theory and Practice of Histotechnology. DC Sheehan, BB Hrapchak.  CV Mosby Company, St. Louis. First edition. 1980.
  3. Luna L.  AFIP. Manual of Histologic Staining Methods.  Third Edition. McGraw-Hill. p39. 1968.  As modified by CM Chapman
  4. Dermatopathology Laboratory Techniques.  CM Chapman, I Dimenstein.  2016.  CreateSpace/Amazon.com.
Histology Safety 102: The Laboratory Standard Part 2

Histology Safety 102: The Laboratory Standard Part 2

The histology laboratory is a dangerous place to work for employees.  Sharp knives, slick floors, hazardous chemicals and bloodborne pathogens are just the main sources of potential accidents.  A way to keep histology laboratory employees safe is to provide information on dangers, explain the ways in which employees can protect themselves, and provide annual training to reinforce this information.  This is not just a good plan.  In most instances, this plan is backed by laws and regulations.  The previous two blogs set the regulatory background for this safety discussion.  This blog will go into the specific, day to day actions that can be implemented to help ensure histology employee safety.

Falls
Accidental falls are the number one threat to safety in the histology laboratory. Laboratory employees should not be at prime risk, as they are supposed to wear non-slip footwear.  However, office staff and visitors are at a very high risk of slipping, falling and being injured.  Many facilities have a carpeted office area.   Office staff becomes accustomed to the particular “coefficient of friction” between their footwear and the carpet.  Then, when they enter the laboratory and step onto the tile floor, this coefficient of friction is very different, and their feet literally slip out from under them.  It is similar to walking along a snow bank, and then stepping out onto ice.  Falls can seriously injure the affected person.  In order to minimize accidental falls, the following recommendations are made:

  • Prohibit all non-laboratory personnel from entering the laboratory.
  • If this cannot be done, mandate that all office staff and visitors coming into the laboratory wear non-slip footwear.
  • A laboratory staff member should accompany any visitor entering the laboratory, and remind them to “walk easy” on the tile floor.

Cuts
Cuts are the second most common threat in the histology laboratory.  Any histologist who is cutting blocks on a rotary microtome is at risk.  While personnel are safer today with the use of disposable blades, there are several occasions when a histologist can get cut.

  • Most disposable blades are provided in an injector type dispenser. When the blade is being dispensed, the histologist runs the risk of pushing the blade across an exposed finger.
  • When the histologist removes or inserts a block into the microtome, it is imperative that the hand wheel is in the locked position. If the wheel is not locked, the downward force of working the chuck can move it downward, into the blade, causing a cut.
  • When a histologist is ready to clean their microtome, the first thing to be done is to lock the hand wheel. Secondly, the disposable knife blade must be removed from the knife holder, and disposed of.
  • Obviously, surgical grossing personnel must be aware of handling sharp blades as well, and exercise extreme caution.

Cuts should be treated with first aid immediately.  The cut should have pressure applied to stop bleeding, and then be rinsed/soaked in Betadine before applying more pressure and a dressing.  The patient should then be transported to the emergency room as soon as possible for treatment.

Waste streams
One of the best ways to ensure safety of laboratory employees from hazards is to mandate designated waste streams in the laboratory.  The following are suggested.

  • Biohazard waste
  • Chemical waste
  • Sharps waste
  • Regular, sterile waste

Biohazard waste must be disposed of according to the Bloodborne Pathogens regulations.  Specifically, biohazard waste must be double red-bagged before being placed into the final container for transport.

(Figure 1). Your licensed waste chemical vendor will help you to determine the profile of each waste, such that it is stored and handled correctly, as well as being labelled correctly. Chemical waste must first be segregated into the proper chemical waste streams

Sharp waste may ultimately go into the biohazard waste, if contaminated (i.e. surgical grossing blades, microtome blades).  However, the blades, and any other sharps in the laboratory must be discarded into a red, hard plastic container first.

The remainder of laboratory waste is regular, sterile waste, generated in the lab.  Paper towels used in handwashing, etc. fall into this category.  Under no circumstances should any of the other three waste streams be discarded into the regular sterile waste stream.

Following the above information and guidelines will help you to prevent injuries to you, your coworkers, and any other support staff that may enter and work in your laboratory.

 

References

  1. Theory and Practice of Histological Techniques. Chapter 10.  JD Bancroft, A Stevens ed.  Churchill Livingstone, NY.  Fourth edition. 1996
  2. Theory and Practice of Histotechnology.  Chapter 9.   DC Sheehan, BB Hrapchak.  CV Mosby Company, St. Louis. First edition. 1980.
  3. CM Chapman.  Histology Study Group.  Presented at Region I meeting,     hosted by MaSH.  2014.
  1. Laboratory Safety. NSH Self Assessment Booklet.  1st  page 33, 2004.]
  2. Hazardous Materials in the Histopathology Laboratory. Dapson and Dapson.  Fourth Edition.  Anatech Ltd.

Histology Safety 102: The Laboratory Standard Part 1

The histology laboratory is a dangerous place to work for employees.  Sharp knives, slick floors, hazardous chemicals and bloodborne pathogens are just the main sources of potential accidents.  A way to keep histology laboratory employees safe is to provide information on dangers, explain the ways in which employees can protect themselves, and provide annual training to reinforce this information.  This is not just a good plan.  In most instances, this plan is backed by laws and regulations.  This current series of blogs will delve into the various regulations, and how laboratories need to be in compliance in order to keep employees safe.

OSHA passed “Occupational Exposure to Hazardous Chemicals in the Laboratory” in January 1990, which is known as the Laboratory Standard.  It is to be used in conjunction with the Hazard Communication Standard and Chemical Hygiene Plan to inform and train employees on the dangers of exposure to hazardous chemicals that they may work with.

Chemical Hygiene Plan

Employers were required to write and implement a Chemical Hygiene Plan (CHP) by January 31, 1991.  At a minimum, the CHP must describe work practices, procedures and policies to protect workers from hazardous chemicals.  The following elements must be part of the CHP:

    • Description of procedures and personal protective equipment (PPE) required to perform specific tasks.
    • Description of specific exposure control methods.
    • Description of methods used to confirm proper operation and function of mechanical controls (i.e. fume hoods, ventilation, etc.).
    • Identification of any procedures hazardous enough to warrant prior approval by the employee before implementation.
    • Description of employee training and medical consultations.
    • Designation of a Chemical Hygiene Officer or Committee.
    • Designation of an area within the laboratory where “select carcinogens” are handled.
    • Description of procedures for the safe removal of contaminated waste, and decontamination procedures.

 

Hazard Communication Standard

This “Right to Know” standard was pre-empted by the Laboratory Standard.  However, some aspects still apply.

      • Material Safety Data Sheets (MSDS) for any hazardous chemical in the workplace must be on file, and available to employees. These are now known as “Safety Data Sheets” (SDS).
      • Employers must have a written hazard communication program. Under the Laboratory Standard, the CHP takes its place.  Note that the Formaldehyde and Bloodborne Pathogen Standards require their own written programs.
      • Hazardous chemicals are required to be labeled with the identity of the chemical and the appropriate hazard warning.
      • Employees must be provided with information and training upon initial assignment and whenever a new hazard is introduced.
      • Employers must provide annual training and reviews.

 

Chemical Storage

The worst thing you can do in your laboratory is to store all the chemicals by alphabetical order.  Each chemical has its own characteristics, detailed in the SDS that will determine the storage conditions.  Additionally, the SDS should spell out what chemical incompatibilities exist- that is, what chemicals to not store it with. 

Chemical Storage Considerations

Light sensitive chemicals must be stored in dark containers in dark, cool storage areas.  Peroxides fall into this category, as do silver salts, dioxane, acetaldehyde, sodium iodide, mercuric chloride and mercuric iodide.  (Note- you should not have any mercury compounds in your laboratory- see theMercury section.)

Acids should be stored by themselves, in an acid cabinet away from formaldehyde, bases, alcohols and oxidizers.

Bleach is a base, composed of 5% sodium hypochlorite.  If it is mixed with formaldehyde or ammonium hydroxide, toxic gases can be released.  Bleach should also not be stored next to acids or methanol.

Flammable compounds such as acetone, xylene and alcohol should never be stored in a regular laboratory refrigerator or freezer.  These chemicals can vaporize and leak from their containers, forming a mixture inside the refrigerator/freezer.  Then, when ignited by a spark (i.e. the condenser unit coming on), they can explode.  Flammables should be stored in a flammable cabinet.

Carcinogens

Some chemicals are capable of causing alterations in the DNA (genetic material).  Changes in the DNA can cause mutations, cancer and or reproductive damage.  These chemicals are referred to as “carcinogens” and are covered separately under the laboratory standard.  They must be kept in a secure and labeled area within the laboratory, and employees must handle them with extreme care, including personal protective equipment and proper ventilation. Current CAP regulations require all chemicals to be assessed for carcinogenicity, reproductive toxicity and acute hazards, as well.

Mercury

There is no need to keep any mercury compounds in the histology laboratory.  There are many substitutes available today.  Do the substitutes work as good as the original mercury compounds?  Sometimes yes, sometimes no.  Do the substitutes work well enough for the pathologist to make a diagnosis?  Most certainly – yes.

You should dispose of your mercury thermometers and replace them with organic filled thermometers as well.  Mercury is a very toxic poison, and has no place in today’s histology laboratory.

References

      1. Theory and Practice of Histological Techniques. Chapter 10.  JD Bancroft, A Stevens ed.  Churchill Livingstone, NY.  Fourth edition. 1996
      2. Theory and Practice of Histotechnology.  Chapter 9.   DC Sheehan, BB Hrapchak.  CV Mosby Company, St. Louis. First edition. 1980.
      3. CM Chapman.  Histology Study Group.  Presented at Region I meeting,     hosted by MaSH.  2014.
      1. Laboratory Safety. NSH Self Assessment Booklet.  1st  page 33, 2004.]
      2. Hazardous Materials in the Histopathology Laboratory. Dapson and Dapson.  Fourth Edition.  Anatech Ltd.
Histology Safety 101 – Formaldehyde

Histology Safety 101 – Formaldehyde

The histology laboratory is a dangerous place to work for employees.  Sharp knives, slick floors, hazardous chemicals and bloodborne pathogens are just the main sources of potential accidents.  A way to keep histology laboratory employees safe is to provide information on dangers, explain the ways in which employees can protect themselves, and provide annual training to reinforce this information.  This is not just a good plan.  In most instances, this plan is backed by laws and regulations.  This current series of blogs will delve into the various regulations, and how laboratories need to be in compliance in order to keep employees safe.

OSHA – The Formaldehyde Standard

Passed in December 1987, the standard protects all workers, laboratory and industry alike.  The standard was revised in May 1992 to incorporate lower exposure limits.  Copies of the standard can be obtained from your local OSHA office, or on line. 

OSHA uses different types of limits for airborne exposures, which reflect Permissible Exposure Limits (PEL). 

Time Weighted Average (TWA) is the airborne concentration averaged over eight consecutive hours.  The TWA for formaldehyde is 0.75 ppm.  No employee may be exposed to more than 0.75 ppm of formaldehyde over eight hours.

Short Term Exposure Limit (STEL) is the airborne concentration averaged over the worst 15 minutes.  The STEL for formaldehyde is 2 ppm.

OSHA has also set an Action Level for formaldehyde of 0.5 ppm averaged over 8 hours.  If this limit is reached or exceeded, the employee must be notified and steps taken immediately to adjust procedures that result in a decrease of the airborne concentration.

Employee monitoring is required to document the exposures existing in the laboratory.  Initial monitoring of each exposed employee is required, unless monitoring has been done previously for a particular job description.  Initial monitoring must be repeated if there is a change in work procedures or control systems.  If an employee displays any exposure symptoms (i.e. respiratory, dermal, etc.) the employee must be monitored immediately.

If either the TWA or STEL is exceeded, the employer can:

  • Install engineering controls, such as increased ventilation.
  • Change work practice controls, such as procedural changes.
  • Provide and require use of respirators.

Periodic employee monitoring depends on the initial monitoring results.

  • If exposure levels are at or above the Action Level of 0.5 ppm, immediate monitoring must be done for each employee or job description and continued until the issue is resolved.
  • If the STEL is exceeded, immediate monitoring must occur and continue until the issue is resolved.

Periodic monitoring may be discontinued if two successive samples taken at least seven days apart are below the Action Level and STEL.

Recommendation: In our laboratory, we monitor employees annually, even though the standard does not require it. We feel it is important for both employer and employee to make certain the work environment is safe for everyone.

Required: Safety goggles, gloves and an impervious gown, as well as access to an eyewash station and safety shower are required when handling formalin, regardless of the exposure limit (Figure 1).

Remember: 

 

blog-13-figure-1-300x126

The above label must be present on EVERY container and specimen bottle of formaldehyde. It is there for a reason.  Formaldehyde is a POISON and CARCINOGEN.  You must handle it with proper personal protective equipment (PPE) using a ventilated work station…always…without exception.

Histology laboratory personnel who change out tissue processors are especially prone to formaldehyde liquid and vapor exposure.  Personnel must wear the PPE described above while handling formaldehyde.  Additionally, when pouring containers of formaldehyde (i.e. from on board tissue processors, into waste containers), employees should be performing this function in a fume hood to prevent exposure.  Alternatively, employees may be fit-tested for a respirator to wear during the handling of formaldehyde.  Goggles, rather than safety glasses, are the eye protection of choice, since they protect against splashes and vapors (Figure 2).

 

References

  1. Theory and Practice of Histological Techniques. Chapter 10.  JD Bancroft, A Stevens ed.  Churchill Livingstone, NY.  Fourth edition. 1996
  2. Theory and Practice of Histotechnology.  Chapter 9.   DC Sheehan, BB Hrapchak.  CV Mosby Company, St. Louis. First edition. 1980.
  3. CM Chapman.  Histology Study Group.  Presented at Region I meeting,     hosted by MaSH.  2014.
  4. Laboratory Safety. NSH Self Assessment Booklet.  1st  page 33, 2004.]
  5. Hazardous Materials in the Histopathology Laboratory. Dapson and Dapson.  Fourth Edition.  Anatech Ltd.

Laboratory Safety Overview

Histology laboratories contain dangers to laboratory personnel in the form of hazardous chemicals, biohazards and physical hazards.  These dangers are minimized by identifying the sources and educating laboratory employees with regard to these sources and the protective equipment and procedures used to minimize and eliminate the dangers.

Engineering Controls

The first line of safety in the histology laboratory is the use of engineering controls.  The histology laboratory should contain at least two fully functional, distinct air handling systems.  The first provides heated/cooled conditioned air to maintain a constant range of temperature and humidity for employees and equipment to optimally function.  The second system is an exhaust ventilation unit, consisting of an exhaust fan located on the roof of the building.  This fan should operate continuously 24 hours, 7 days a week. It is attached via ductwork to all ventilated workstations and chemical fume hoods located in the laboratory space.  Employees are instructed to use ventilated work stations when working with hazardous chemicals and biohazardous specimens.  Additionally, there may be laminar flow hoods in the laboratory for use with biohazardous specimens.

Personal Protective Equipment 

All laboratory personnel must be instructed in the proper use of personal protective equipment (PPE).  This equipment includes, but is not limited to: safety glasses, safety goggles, face shields, non-latex gloves (i.e. nitrile), lab coats and/or impervious protective gowns and N95 respirators.  The exact PPE required for each task is to be described via placard in each appropriate work station in the laboratory, as well as providing direct instruction to each laboratory employee.  Each specific task in the laboratory must be assessed for potential safety impact, resulting in the specification of PPE for that task.  All employees must comply by utilizing the specific PPE, which must be provided by the employer at no cost to the employee.

Safety Training

All laboratory employees must be given safety training upon initial assignment and annually thereafter.  All employees are then required to review the laboratory safety manual annually.  The laboratory safety manual must be available in the work area at all times.  The laboratory safety manual should include sections on General Safety Policies, Fire Prevention/Disaster Plans, Chemical Hygiene Plan/Hazardous Materials/Formaldehyde Standard, Biohazard Policy/Bloodborne Pathogens, Accident First Aid/Reporting, Ergonomics, and Equipment Safety, at a minimum.

Safety Corner

There should be a source of everyday safety information and it is suggested to have a “Safety Corner” located in the laboratory.  Pertinent safety information is posted for all employees and includes:

  • Fire extinguisher operation – PASS

[Pull the safety pin / Aim the nozzle at the base of the fire / Squeeze the handle / Sweep the base of the fire.]

  • Fire Discovery procedure – RACE

[Rescue / Activate Alarm / Confine the Fire / Evacuate, Extinguish]

  • Evacuation map
  • Disaster evacuation directions
  • Chemical spill procedure
  • MSDS binders / access to online MSDS
  • OSHA 300A log
  • List of emergency contact numbers

General Safety Rules and Instructions

While all safety procedures are contained in the laboratory safety manual which all employees have access to, the following general safety rules are universally adopted and should be included in any and all safety instruction.  All laboratory personnel are expected to be familiar with the following safety concepts.

  1. There is no smoking in the laboratory or building.
  2. There is no eating or drinking in the laboratory.
  3. Every task in the laboratory has specific PPE designated to be used.
  4. Any and all waste must be deposited in one of the following waste streams:
    • Chemical waste: waste drums are provided.
    • Biohazardous waste: double red bag biohazard containers are provided.  All gloves are to be disposed of here.
    • Sharps waste: hard plastic sharps containers are provided.
    • Sanitary waste: regular trash barrels are provided.
  1. All waste is properly manifested for legal disposal by licensed companies.
  2. Proper closed toe, rubber soled footwear must be worn in the laboratory.
  3. Ventilated workstations must be used when handling chemicals and/or biohazardous materials.

In summary, it is the responsibility of the employer to provide safety training and PPE to laboratory personnel, and it is the laboratory employees’ responsibility to use proper PPE and follow all safety procedures.  This is the only way to guarantee everyone’s safety while working in the laboratory.

Proper receipt and handling of histology specimens

If you have worked in the histology field for some time, as I have, you may have noticed that the specimens you receive in your laboratory are getting smaller. This is not due to our failing eyesight. Instead, the advances in immunohistochemistry (IHC) and molecular techniques now enable the pathologist to make diagnoses on smaller and smaller fragments of tissue obtained during biopsy procedures. This fact, along with the emphasis on greater patient care quality, requires that each and every specimen received in your laboratory must be routed to the correct area, and handled appropriately.

In non-specialty hospital and private reference histology laboratories, the vast majority of specimens are received in 10% neutral buffered formalin for “routine histology”. This means specimens will undergo surgical grossing procedures and routine processing through graded alcohols, xylene and paraffin embedding. Initial hematoxylin and eosin (H&E) stained slides will be prepared from paraffin blocks. Upon review by a pathologist, a diagnosis is rendered. Some cases may require additional IHC, molecular and/or special stains to confirm the diagnosis.

Some specimens may be received in formalin into the routine lab; however, they may require “non-routine” handling. Skin specimens submitted for “Slow Mohs” processing are such specimens. These are pieces of skin that are carefully marked with colored inks to indicate exact orientation. Laboratory personnel who receive the specimens, and who perform the surgical grossing techniques must recognize these “up front”. Failure to recognize such specimens may result in changing/destroying the orientation, resulting in the pathologist’s inability to render an accurate diagnosis with regard to tumor location with respect to surgical margins.

Similarly, a two millimeter punch specimen of skin may be mishandled by laboratory staff, if not identified “up front” at the time of receipt. These specimens should be identified for embedding and microtomy personnel. The microtomy personnel must pick up the very first sections, and observe the unstained slide under the microscope to ensure correct dermal-epidermal orientation. If the specimen has been mis-embedded, there is enough tissue to melt down and re-embed correctly. Failure to follow this procedure may result in the production of initial and level slides that are mis-embedded. The final result may be that the specimen cannot be diagnosed.

An inherent danger exists in the minority of specimens that may be received for unique, specialized procedures. If these specimens are received in the incorrect fixative, or routed into the “routine histology” workflow, they may be unable to be used in the specialized procedures for which they were sent to the laboratory.

Specimens for direct immunofluorescence (DIF) are usually skin and kidney biopsies. Clinicians must be educated to ensure that these specimens are not fixed in formalin. Instead, these specimens must be submitted in “Michel’s transport medium”, sometimes labelled “Immuno transport fluid”. This solution contains ammonium sulfate, which acts to precipitate proteins at their precise site of localization. This enables the frozen sections prepared to be stained with fluorescein labelled antibody preparations, in order to pinpoint the exact histological location of the proteins in question. Use of formalin fixation causes crosslinking of these proteins, which subsequently changes the antigenicity, making the proteins unable to be recognized by the antibodies.

Two specimen types may be received for urate crystal evaluation: both tissues and fluids may be submitted by clinicians. Joint fluids obtained by fine needle aspiration may be submitted – still contained within the syringe. These specimens must not be fixed in formalin or cytology fixatives. Instead, the fluid should be dispensed on to a clean, labelled microscope slide, using ventilation and Universal Precautions (i.e. the fluid may contain active, blood borne pathogens). After air drying, the slide is cover slipped with Permount and observed under polarizing light.

Similarly, a tissue specimen must be submitted in either Carnoy’s fixative (chloroform and absolute ethanol) or simply absolute ethanol. Fixation cannot be in formalin, as formalin contains water which may dissolve any urate crystals that are present. Once received, the specimen must be processed from 100% ethanol, skipping over the formalin and graded alcohol series in the tissue processor. Once processing and embedding are complete, a slide for H&E and an unstained slide should be prepared. The unstained slide should be rinsed in xylene to remove the paraffin, and then cover slipped. As described above, the unstained slide is viewed under polarized light. Urate crystals will appear as bright white needles on a black background.

In summary, it is excellent practice to identify any and all specimens that may be received by your laboratory for “non-routine” histology. Once identified, procedures should be developed for proper receipt and handling of the specimens. This is the only way to ensure the highest patient care quality.