Key Points Flashcards
What Is Epidemiology?
Epidemiology
Epidemiology, unlike clinical medicine, is population-based, and so it is useful for describing health-related phenomena in groups of people. Although epidemiology studies groups of people rather than an individual patient, its principles are used widely in all areas of healthcare. Epidemiology provides information for community and preventive medicine, analysis of health assessments, safety programs, utilization review and management of resources, and health planning and forecasting.
Carriers
Epidemiological Models
The following are two crucial concepts to understand with regard to carriers:
- Some diseases may be transmitted by a carrier before they become symptomatic.
- Some carriers may live long and healthy lives with the organism present.
Both of these circumstances present a particular risk of transmission to susceptible hosts in the healthcare setting because they are less likely to be recognized. There may be no indication that they are ill or that they may be infectious. Precautionary measures to prevent transmission are less likely to be instituted because illness is not apparent.
Mode of Transmission
Epidemiological Models
It is important to understand that some agents (bacteria, viruses, toxins, etc.) may have more than one mode of transmission.
Susceptible Host
In addition to these characteristics, the susceptible host has several nonspecific defense mechanisms that may modify the risks of becoming infected and developing disease. These include normal flora, the host’s natural antibodies, natural barriers of entry, and good nutritional status.
Breaking the Chain
By breaking the chain of infection at any of the links, the transmission of infection is stopped:
- The infectious agent is eliminated or inactivated or cannot survive in the reservoir (e.g., rapid identification and management of organisms, cleaning and disinfecting of the environment).
- The portal of exit is managed through good infection prevention and control practices (e.g., hand hygiene, appropriate use of PPE, safe packaging, disposal of waste).
- Transmission does not occur due to good infection prevention and control practices (e.g., hand hygiene, isolation of infected patients, air flow control where appropriate).
- The portal of entry is protected (e.g., aseptic non-touch technique, safe catheter care, wound care).
- The susceptibility of patients receiving healthcare is reduced (e.g., treatment of underlying disease, recognizing high-risk patients).
Surveillance Importance and Principles
Surveillance plays a critical role in identifying outbreaks, pandemics, emerging infectious diseases, multidrug-resistant organisms, and bioterrorist events so that infection prevention measures can be instituted; it also helps in establishing a baseline (endemic level).
Interdisciplinary Teams
Surveillance programs in healthcare organizations should be integrated to include infection prevention and control, performance improvement, patient safety, emergency preparedness, and public health activities.
IPC Surveillance
IPC surveillance is a collaborative exercise: An IP does not, and should not, work alone. It is essential that they assemble an interdisciplinary team with a broad range of relevant skills and expertise.
Identifying Goals and Objectives
The primary goal for all surveillance programs is to prevent and control HAIs and improve patient outcomes. Surveillance goals and objectives are based on the findings in the facility’s risk assessments.
Process for Creating a Surveillance Plan
An important prerequisite to developing a facility- and population-appropriate surveillance plan is for the IP to review the facility’s risk assessments for the specific risks that have been identified as priorities. This will direct surveillance purpose, events to monitor, data to collect, etc.
Methodologies
It is important to select an appropriate surveillance and data collection methodology. When choosing a methodology, IPs should consider their facility’s needs and requirements, available resources, and identified goals and objectives.
Process Measure Interventions
Surveillance examines both outcomes and processes. Understanding how processes are conducted can generate valuable information and recommendations to help reduce or stop the transmission of infections.
Identifying Surveillance Criteria
Surveillance data must be collected using standardized criteria. This facilitates the accurate identification of trends and the comparison of data from multiple surveillance programs, and it supports benchmarking.
Data Requirements Related to Selected Data Analysis Methods
Whenever possible, data should be expressed as rates or ratios that are calculated using the same methodology as a nationally validated surveillance system. This allows an organization to compare its rates with those of another organization or a recognized benchmark.
Surveillance Data Sources A
The IP should carefully consider the sources of available data to determine which are most important for their surveillance programs. This ensures that relevant data are collected and resources are not misused.
Surveillance Data Sources B
Surveillance data should be collected on a routine, systematic, and ongoing basis. The entire interdisciplinary team should be involved in data collection.
Need for Statistical Analysis
Data are useful only if they can be turned into comprehensible and actionable information. IPs must become familiar with the various methods for data analysis.
Association
A causal association or relationship should not be confused with causality. A causal association is a necessary component of causality; however, there are a number of other conditions that must be satisfied for something to be described as causality.
Association Versus Causation
Statistics cannot prove either an association or causality; it can merely suggest that an association exists.
Relative risk (RR) and Odds ratio (OR)
For both RR and OR, as the value increases in distance from 1.0, the likelihood that a relationship exists between the factors being examined increases as well. For example, an odds ratio of 8.6 indicates a higher likelihood of a relationship between two factors than does an odds ratio of 2.3.
Types of Statistics
There are two types of statistics: descriptive and inferential. Descriptive statistics provides numerical information about variables. In simple terms, it uses numbers to describe the characteristics of a data set. Inferential statistics makes an assumption (an inference) about a population based on a sample or calculates the strength of the association between cause and effect.
Stratification and Standardization in Descriptive Statistics
Without stratification, internal comparisons of rates over time or external comparisons are likely to be invalid or misleading. However, if rates are stratified, subpopulation sizes must be large enough to be statistically meaningful.
Measures of Frequency
Calculating ratios, proportions, and rates is an important part of any surveillance program, as these measurements help transform raw data into actionable information.
Incidence
The number of new cases of a given disease in a given time period. For example, the number of newly diagnosed cases of active tuberculosis in a calendar year in a given county is the incidence of tuberculosis in that county, or the number of new CLABSIs (central line-associated bloodstream infections) in the intensive care unit in January is the incidence of CLABSI in the ICU in January.
Quantitative data
Are numeric—that is, they are collected by counting (people, behaviors, conditions, infections, etc.). They can be used to make comparisons. Quantitative data can be further classified as discrete or continuous:
Discrete data contain whole numbers and represent a finite number of values—for example, the number of patients admitted to a unit on a given day. Discrete data are counted.
Continuous data contain whole numbers, decimals, or percentages that can be measured on a continuum or scale and can have numeric values between minimum and maximum values (a continuum)—for example, patient age, infection rates, or temperatures. Continuous data are measured rather than counted—for example, the standardized infection ratio (SIR) versus the infection rate over a two-year period.
Qualitative data
Include all data that are non-numeric. They use words to describe healthcare events. Examples of qualitative variables include patient blood type (i.e., A, B, AB, O) and infection status (infected, not infected).
Categorical data
Are data that fit into mutually exclusive groups—for example, sex, age group, and organism. It is easy to make quantitative data categorical, such as transforming age in years into age groups.
Reliability Tests, Sensitivity, and Specificity
In order to remember the difference between sensitivity and specificity, a good rule of thumb is that a high sensitivity test is one where a negative result rules out the existence of a disease and a high specificity test is one where a positive result confirms the existence of a disease.
For example, if a diagnostic test has a high sensitivity (95%), it should correctly detect the presence of a disease 95% of the time, and the false negative rate would be low, at 5%.
In contrast, if a diagnostic test has a high specificity (95%), it should correctly identify the absence of a disease 95% of the time, and the false positive rate would be low, at 5%.
To help prevent confusion on which values or boxes of the 2 by 2 chart should be in the above calculations, a few observations may be useful.
- For each of the above formulas, only two of the four boxes in the 2 by 2 test are used as the numerator: the true positive (upper left box) and the true negative (lower left box).
- In each formula, the value used in the numerator is part of the calculation for the denominator.
- No formula uses values from more than two boxes.
Data Presentation
When compiling information to be shared with stakeholders, it is important to provide full names of infections, diseases, and so forth. Do not assume that they are familiar with acronyms or shortened forms of names. If using acronyms, best practice is to provide a key to aid stakeholder understanding.
Spot and Area Maps
The visual representation of data better conveys the significance of surveillance findings—and more easily guides decision making—than the presentation of the raw data set does.
Statistical Process Control
Statistical control refers to the stability and predictability of a process over time. Statistical process control (SPC) is a set of methods, such as a control chart, that can be used for improving systems, processes, and outcomes.
The primary goal of SPC is to recognize and understand common cause and special cause variations that affect a process. Common cause variability represents the expected level of variability and is not due to external factors; rather, this variation is from internal factors inherent in the nature of the system. Special cause variations can be attributed to an external factor. A process with special cause variation is said to be out of statistical control. Examples of special cause variation include human error and mechanical malfunction.
Control Charts
At least 25 data points are necessary to construct a proper control chart. With fewer than 25 data points, it is difficult to detect special cause variation.
Internal and External Reports
Communication is an essential component of any surveillance or outbreak investigation. IPs must know what to report, how and when to report, and to whom they should report. IPs familiarize themselves with internal and external reporting requirements in order to ensure that relevant stakeholders and partners receive the information they need.
External Communication
Sharing appropriate surveillance information with internal and external stakeholders ensures that others can prepare and allocate resources; it can also help expand surveillance activities to acquire more and more relevant data.
Mandatory reporting requirements ensure that healthcare facilities are in compliance with local and national standards.
Need for Infection Preventionists in Emergency Preparedness
While interventions will vary with different types of disasters, the general principles of surveillance and epidemiology remain the same.
Disaster Scope and Types
Natural disasters may take many forms, and whether or not they are a concern for a facility depends heavily on the facility location and characteristics. In emergencies such as issues with water supply or an electrical outage, the IP may have an assigned role, such as to prevent/control waterborne illness or food/vaccine spoilage. The IP (and all other facility HCP) should be aware of the specific risks to their facility and their duties during any emergencies that may occur.
Emerging Infections
As experts in the fields of communicable diseases, infection prevention and control, and epidemiology, infection preventionists are poised to be at the forefront of an infectious disease disaster. As such, they must embrace their role as experts in infectious disease emergency management and assist their healthcare facility or community in becoming better prepared to rapidly, appropriately, and effectively respond.
Emergency Communication Preparations
Note that the IP may receive information requests from the media and other parties in nonemergency situations, in which case they will need to refer to the established organizational structure and follow the proper chain of command to respond to the inquiry.
What Is an Outbreak?
One of the most important aspects of managing an IPC program is identifying high-risk patient populations and the potential pathogens that could lead to an HAI. An annual program risk assessment is essential to help identify the populations at risk in a healthcare facility.
Of equal concern are communicable diseases that can be spread to the HCP population. Depending on the exposure, HCP may require post-exposure prophylaxis (PEP). At that juncture, consultation with an infectious disease physician or review of current guidelines (e.g., from the CDC) is essential to ensure optimal medical care and screening for HCP.
Goals of Outbreak Investigation and Control Measures
The goal of any outbreak investigation is to control the outbreak by identifying and modifying contributing factors and to develop and implement measures to prevent similar outbreaks in the future.
Notifying and Involving Key Stakeholders
Communication is a core competency for any IP, especially in surveillance and when managing an outbreak. The ability to communicate and collaborate with other staff members is essential.
Defining the Outbreak
Factors associated with the agent, the host, or the environment contribute to the development of the outbreak, and modification of one or more of these factors holds the potential elements to end the outbreak.
Preparing an Initial Line List and Epidemic Curve
The line list is an invaluable tool for an IP. It is used to collect together all relevant information on suspected outbreak cases. These data can be used to track and analyze the event, both during the outbreak and after it has ended.
Follow-Up Activities
Generally, if active surveillance has been in place and no new cases have been identified during a period twice as long as the incubation period, measures can be discontinued.
