Fifty years ago, Spaulding8 devised a rational approach to disinfection and sterilization of patient care items and equipment. This classification scheme is so clear and logical that it has been retained, refined, and successfully used by infection control professionals and others when planning methods for disinfection and sterilization.4, 5, 6, 7, 8, 9, 10 Spaulding believed that the nature of disinfection could be understood more readily if instruments and items for patient care were divided into 3 categories based on the degree of risk of infection involved in the use of the items. The 3 categories he described were critical (enters sterile tissue and must be sterile), semicritical (contacts mucous membranes or nonintact skin and requires high-level disinfection), and noncritical (comes in contact with intact skin and requires low-level disinfection). These categories and the methods to achieve sterilization, high-level disinfection, and low-level disinfection are summarized in Table 1. Although the scheme remains valid, there are some examples of disinfection studies with prions, viruses, mycobacteria, and protozoa that challenge the current definitions and expectations of high- and low-level disinfection.11
Critical items
Critical items are so-called because of the high risk of infection if such an item is contaminated with any microorganism, including bacterial spores. Thus, it is critical that objects that enter sterile tissue or the vascular system be sterile because any microbial contamination could result in disease transmission. This category includes surgical instruments, cardiac and urinary catheters, and implants. The items in this category should be purchased as sterile or sterilized by steamsterilization, if possible. If heat-sensitive, the object may be treated with ethylene oxide, hydrogen peroxide gas plasma, vaporized hydrogen peroxide, hydrogen peroxide vapor and ozone, or liquid chemical sterilants, if other methods are unsuitable. Table 1, Table 2, Table 3 list sterilization processes, high-level disinfectants, and liquid chemical sterilants and the advantages and disadvantages of each. With the exception of 0.2% peracetic acid (12 minutes at 50°C-56°C), the indicated exposure times for liquid chemical sterilants range from 3 to 12 hours. Liquid chemical sterilants can be relied on to produce sterility only if cleaning, which eliminates organic and inorganic material, precedes treatment and if proper guidelines as to concentration, contact time, temperature, and pH are met. Another limitation to sterilization of devices with liquid chemical sterilants is that the devices cannot be wrapped during processing in a liquid chemical sterilant; thus, it is impossible to maintain sterility following processing and during storage. Furthermore, devices may require rinsing following exposure to the liquid chemical sterilant with water that, in general, is not sterile. Therefore, because of the inherent limitations of using liquid chemical sterilants in a nonautomated (or automated) reprocessor, their use should be restricted to reprocessing critical devices that are heat-sensitive and incompatible with other sterilization methods.
Sterilization technologies can be relied on to produce sterility only if cleaning—to eliminate organic and inorganic material as well as microbial load—precedes treatment.12, 13, 14 Other issues sterile reprocessing and operating roomprofessionals must deal with when reprocessing instruments include weight limits for instrument trays, wet packs, packaging, loaned instruments, cleaning monitoring, and water quality.14, 15
In May 2015, the Food and Drug Administration (FDA) convened a panel to discuss recent reports and epidemiologic investigations of the transmission of infections associated with the use of duodenoscopes in endoscopic retrograde cholangiopancreatography procedures.16 After presentations from industry, professional societies, and invited speakers, the panel made several recommendations, to include reclassifying duodenoscopes based on the Spaulding classification from semicritical to critical to support the shift from high-level disinfection to sterilization. This could be accomplished by shifting from high-level disinfection for duodenoscopes to sterilization and modifying the Spaulding definition of critical items from “objects which enter sterile tissue or the vascular system or through which blood flows should be sterile” to “objects which directly or indirectly (ie, via a mucous membrane such as duodenoscope) enter normally sterile tissue of the vascular system or through which blood flows should be sterile.”3,17, 18, 19 It is noteworthy that in the Spaulding scheme, which identifies how an object should be disinfected or sterilized, he stated that mucous membranes should be intact and that sterilization of semicritical items is desirable.8 Implementation of this recommendation requires sterilization technology that achieves a sterility assurance level of 10−6 of complex medical instruments such as duodenoscopes. Ideally, this shift would eventually involve not only endoscopes that indirectly enter normally sterile tissue (eg, duodenoscopes, bronchoscopes) but also other semicritical devices (eg, gastrointestinal endoscopes).17