Letters (Validation of transfer techniques)
From Mr P. J. Maltby and Dr R. E. Stringer
The pilot study (PDF*
95K) on validation of transfer techniques into hospital pharmacy clean
rooms by Cockcroft et al (Hosp Pharm, September, 2001, pp226–32)
is to be welcomed. However, it is not sufficient in extent or depth to
support recommendations for changes in current working practices.
The authors have missed the opportunity for the
application of statistical techniques, from the study design through to
the analysis of the results. For instance, there seems little point in
only testing one or two items of a particular type of consumable. Furthermore,
the paper draws unsupported conclusions, such as there being a difference
in the efficacy of disinfection techniques when challenging with the organisms
S. aureus and C. albicans, whereas the data presented fail
to show a statistically significant difference.
The over-challenge with bacillus spores seems excessive:
480 times the maximum number of organisms observed under normal conditions
cannot be regarded as realistic. It is questionable whether extrapolating
from the results of this over-challenge allows conclusions to be drawn
which apply to "normal" conditions. If a production unit is known to have
a problem with contamination of this kind then there may be an argument
for adoption of a combination wipe/spray technique. In the absence of
"local" evidence indicating a problem, is there any basis for changing
current practice?
It would be useful to assess inter- and intralaboratory
differences in bio-burden estimation as well as operator disinfection
technique. In practice, it may be difficult for operators to consistently
implement the suggested "wipe" procedure and some method of validation
of operator wipe technique needs to be considered. Bearing in mind the
costs of operators' time and of the consumables required for the implementation
of the suggested technique, some form of cost-benefit analysis might be
advantageous.
Any recommendations should take into account existing
"in-house" validations of component transfer and storage. The paper has
raised some very interesting and thought provoking questions and we look
forward to the results of further work.
Paul Maltby
Principal radiopharmacist
Rebecca Stringer
Senior radiopharmaceutical scientist
Radiopharmacy department
Royal Liverpool and Broadgreen University Hospitals
NHS Trust
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Mr Cockcroft and colleagues reply:
The work on liquid disinfection
techniques was undertaken following concern by Medicines Control
Agency (MCA) inspectors about the widespread practice of spraying
items in order to decontaminate them before transfer into a pharmacy
aseptic unit clean room. An in house "validation" procedure by pharmacy
staff using contact plates and swabs was not acceptable because
it did not, in the MCA inspector's view, represent a meaningful
challenge. It was not possible to rigorously test all the types
of item to be disinfected and the range of potential challenge micro-organisms.
The writers are correct in assuming
that further work is being undertaken, in fact, along the lines
that the correspondents have indicated. However, having completed
the work published in the article, and having shown the results
to the MCA as a response to inspection, the authors felt that the
conclusions were too important to delay publishing. The work shows
clearly that if spores are present, spraying alone is potentially
insufficient to reduce the bioburden to a level acceptable for manipulation
in a cabinet or isolator.
The authors would have liked to
have applied a number of statistical tests to the results but felt,
as did the external assessor, that the number of results was insufficient
for valid statistical conclusions to be drawn, and hence general
conclusions were presented. The 480 times over-challenge of bacillus
referred to in the letter represented one of the seven challenges
undertaken. It gave a similar pattern of reduction as the other
six challenges, namely, spraying may reduce the bioburden slightly
but wiping is much more efficient and a combination of spraying
and wiping gave the best results.
The authors recognise that replacing
spraying with spraying and wiping will increase the length of time
taken to transfer items into a clean room for those units not already
doing this. However, it is important that quality assurance and
production pharmacists recognise the potential problem of sporicidal
contamination and assess carefully items to be transferred into
the clean room, their packaging and storage conditions. In routine
work of testing and assessing clean rooms, problems with the condition
and storage of plastic rings for lipid bottles (supplied loose in
corrugated cardboard boxes), sharps bins (often requiring washing
before they are fit for decontamination) and trays (occasionally
washed and dried in uncontrolled environments) have been observed.
Collation rooms that are not under positive pressure are a significant
risk. Most of all, building work presents an unquantifiable risk
and extra care and additional disinfection stages are required to
maintain the aseptic unit. The paper presents a strong justification
for considering double or triple wrapped sterile components and
multiple syringe packs.
Martin Cockcroft, John Rhodes
and Alison Beaney
Stockton Quality Control Laboratory
Stockton-on-Tees
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