What to do with contaminated cytospin machine
| What to do with contaminated cytospin machine |
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January 2010
A. CJD is one of the transmissible spongiform encephalopathies (TSE), also known as prion diseases, which are fatal, degenerative brain diseases. Because the TSE agents remain infectious for years in a dried state and resist all routine sterilization procedures, they represent a special challenge for health care facilities whenever instruments are used to process specimens from patients suspected to have CJD. Cerebrospinal fluid is considered a “low infectivity” tissue, along with kidney, liver, lung, lymph nodes, spleen, and placenta. This is in contrast to brain, spinal cord, dura mater, pituitary, and eye, which all are categorized as “high infectivity” tissues. Despite the fact that CSF is considered to be of low infectivity, it is felt that instruments contaminated by CSF should be handled in the same manner as those that have been in contact with high-infectivity tissues in high-risk or at-risk patients. The most effective decontamination process is incineration, which can be used for all instruments, effluent materials, and solid waste. For heat-resistant reusable instruments that an institution is unwilling or unable to incinerate, a decontamination process is recommended; it consists of removing adherent particles through a mechanical or manual cleaning process followed by immersing the instrument in 1N NaOH or two percent sodium hypochlorite solution for one hour, then rinsing and sterilizing by heat. (See exact protocol in Table 6 in the reference provided.) Of note, it is said that “if the instrument or surface cannot be fully immersed or flooded with the chemical disinfectant, then the item must be incinerated.”1 This seems to apply, unfortunately, to cytospin machines and to other equipment. An alternative procotol can be used to safely make slides from CSF specimens without using any special equipment when it is known in advance that CSF from a suspected case of CJD has been submitted. The protocol is a modified Saccomanno’s technique, without need for a cytospin machine. The salient details include inscribing a hydrophobic ring, about the diameter of a nickel, onto a microscope slide using a wax pencil or piece of paraffin. Commercially available microscope slides also are available with a hydrophobic Teflon border from Structure Probe Inc. (www.2spi.com/catalog/new/ptfesld.shtml). The hydrophobic border creates a virtual “well” on the slide to contain the cells. Saccomanno’s fixative is added to the CSF sample at greater than 1:1 volume. The sample is then capped and centrifuged to pellet the cells. The supernatant is decanted into bleach to leave one to two drops of residual material that is then resuspended with a disposable pipette into the center of the well. The slide is laid flat and the liquid allowed to evaporate (about 30 minutes), leaving alcohol-fixed adherent cells on the slide. The slide can then be stained in disposable coplin jars or by adding stain dropwise to the well. Reference 1. Canada Communicable Disease Report. Infection Control Guidelines: Classic Creutzfeldt-Jakob Disease in Canada. Health Canada ISSN 1188–4169, vol. 28S5, November 2002, p.84 (www.phac-aspc.gc.ca/public/ccdr-rmtc/02vol28/28s5/index.html). Manon Auger, MD, FRCP(C) |
Q. Although our cytopathology laboratory policy is to not accept cerebrospinal fluid for processing, we unknowingly processed two CSF samples from a patient who was later diagnosed with Creutzfeldt-Jakob disease (CJD). What should be done with the cystospin machine used to process the specimen?