Biomedical Engineering Reference
In-Depth Information
surfaces lend themselves as more effective substrates for microbial adhesion
and also augment the capability for microorganisms to maintain their physi-
cal juxtaposition enduring cleaning (retention). The relative risk of microbial
retention on equipment surfaces can be determined and described in arbi-
trary but representative terms by ascribing risk scores to those equipment
features that are contributing risk factors. Such risk factors may include
surface hydrophobicity and surface roughness; those risk factors lending
themselves more to microbial adhesion and retention are assigned higher
risk scores. Table 10.4 summarizes the risk factors associated with products
and equipment that lend themselves to elevated risks of microbial adhesion
to surfaces. Typical characteristics and attributes of associated bioburden
and inherent features permit the truly rationale assignment of risk factor
values. These values can be used to determine the worst-case combination
of product and equipment for expediting cleaning and hold validations. This
exemplifies how the subjectivity of risk factor value (or risk factor score)
assignment can be diminished by the tabulation of criteria and risk factor
features that genuinely lend to risk. Products and raw materials will have
varying microbial-growth-supportive capabilities. The selection of aseptic
interventions for incorporation into process simulations might be equally
benefited from the refinement and adaptation of techniques reported by
Akers and Agalloco [23] and Whyte and Eaton [24]. Aseptic interventions
represent events that clearly bring a large and diverse source of microbial
hazard, harboring upon the human body close to the product. The degree
of movement, the duration of the aseptic intervention, and the proximity
to vulnerable product vary between interventions. No one intervention is
identical and therefore elicits its own individual level of risk to product
contamination. Describing risk factors (for example, duration, effort, prox-
imity to product) and assigning risk scores in a manner consistent with the
previously described methods permits the ranking and grouping of interven-
tions based on their potential impact to product sterility. These data may
then be used to decide the selection and incorporation of worst-case aseptic
interventions into a process simulation program.
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Assistance in batch disposition
. Formulaic risk assessments must be regular
activities regularly revisited, maintained as a living document, and perpet-
uated in a state of currency. Furthermore, risk assessments must not only
be applied under exceptional circumstance to assist with decisions of prod-
uct quality. Exceptional circumstances include those occasions involving
unplanned events, leading to uncertainty over the quality or sterility of a
product. Often, the analysis of risk is applied as a one-off means of evalu-
ating the nature of a critical quality attribute and justifying the disposition
of the product. Such preferential and exceptional analysis of risk associated
with a product can send an unfortunate message to regulatory agencies and
undoubtedly color their opinion. There is, however, significant, and as yet
widely unrealized, merit in the routine application of formulaic, quantitative
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