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CBIC CIC practice questions

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Question 1Identification of Infectious Disease Processes

Which bacterial structure is composed of peptidoglycan and determines the Gram stain reaction?

  1. Pilus
  2. Capsule
  3. Flagellum
  4. Cell wall Correct answer.

Explanation

The bacterial cell wall contains peptidoglycan, which retains the crystal violet-iodine complex in gram-positive cells and is thin in gram-negative cells, driving the Gram stain result. Capsules, flagella, and pili are surface structures that do not determine Gram staining.

Question 2Identification of Infectious Disease Processes

Which medium is selective for gram-negative rods and differential for lactose fermentation?

  1. MacConkey agar Correct answer.
  2. Blood agar
  3. Chocolate agar
  4. Thayer-Martin agar

Explanation

MacConkey agar contains bile salts and crystal violet that inhibit gram-positive organisms, plus lactose and a pH indicator that differentiates lactose fermenters from nonfermenters. Blood agar is nonselective, chocolate agar is enriched, and Thayer-Martin is selective for Neisseria.

Question 3Identification of Infectious Disease Processes

Which property is characteristic of enveloped viruses?

  1. They lack a protein capsid
  2. They are inactivated by detergents Correct answer.
  3. They replicate without a host cell
  4. They resist inactivation by ethanol

Explanation

Enveloped viruses have a lipid bilayer that is disrupted by detergents, alcohols, and drying, making them relatively fragile in the environment. Nonenveloped viruses lack this lipid layer and are generally more resistant to such agents.

Question 4Identification of Infectious Disease Processes

Which body site is normally sterile in a healthy adult?

  1. Oropharynx
  2. Bloodstream Correct answer.
  3. Colon
  4. Skin

Explanation

The bloodstream is normally sterile, and recovery of an organism from blood generally indicates infection or contamination. The skin, oropharynx, and colon are colonized by complex normal flora.

Question 5Identification of Infectious Disease Processes

Which genus forms heat-resistant endospores that survive routine disinfection?

  1. Clostridium Correct answer.
  2. Staphylococcus
  3. Neisseria
  4. Escherichia

Explanation

Clostridium species form endospores that resist heat and many disinfectants, allowing survival in adverse environments. Staphylococcus, Escherichia, and Neisseria do not form spores.

Question 6Identification of Infectious Disease Processes

Prions consist primarily of which material?

  1. RNA
  2. Lipopolysaccharide
  3. Misfolded protein Correct answer.
  4. DNA

Explanation

Prions are infectious agents composed mainly of a misfolded isoform of the prion protein, which lacks detectable nucleic acid. This abnormal protein propagates by inducing misfolding of normal prion protein.

Question 7Identification of Infectious Disease Processes

Which fungus typically shows budding yeast cells and pseudohyphae on microscopy?

  1. Cryptococcus neoformans
  2. Aspergillus fumigatus
  3. Candida albicans Correct answer.
  4. Mucor species

Explanation

Candida albicans is a dimorphic fungus that commonly appears as budding yeasts with pseudohyphae in clinical specimens. Aspergillus forms septate hyphae, Mucor forms broad nonseptate hyphae, and Cryptococcus is an encapsulated yeast without pseudohyphae.

Question 8Identification of Infectious Disease Processes

A sputum specimen is evaluated for culture; which finding suggests the sample is saliva rather than lower respiratory secretions?

  1. Few epithelial cells
  2. Predominant gram-positive cocci in pairs
  3. Many squamous epithelial cells Correct answer.
  4. Presence of neutrophils

Explanation

Numerous squamous epithelial cells indicate oropharyngeal contamination and suggest the specimen is saliva. An acceptable sputum specimen typically shows many neutrophils and few squamous epithelial cells.

Question 9Identification of Infectious Disease Processes

A Gram stain of cerebrospinal fluid shows gram-negative diplococci. Which organism is most likely?

  1. Haemophilus influenzae
  2. Neisseria meningitidis Correct answer.
  3. Streptococcus pneumoniae
  4. Listeria monocytogenes

Explanation

Neisseria meningitidis is a gram-negative diplococcus and a leading cause of bacterial meningitis, often appearing within neutrophils in CSF. Streptococcus pneumoniae is a gram-positive diplococcus, Haemophilus influenzae is a gram-negative coccobacillary rod, and Listeria is a gram-positive rod.

Question 10Identification of Infectious Disease Processes

Which specimen is routinely unacceptable for anaerobic culture because of contamination with normal flora?

  1. Blood
  2. Superficial wound swab Correct answer.
  3. Pleural fluid
  4. Bone biopsy

Explanation

Superficial wound swabs are easily contaminated by normal skin and mucosal flora and are generally unsuitable for anaerobic culture. Normally sterile specimens such as blood, pleural fluid, and bone biopsy are appropriate for anaerobic culture.

Question 11Identification of Infectious Disease Processes

Which feature of Mycobacterium tuberculosis explains its acid-fast staining?

  1. Absence of peptidoglycan in the wall
  2. Presence of a polysaccharide capsule
  3. High mycolic acid content Correct answer.
  4. Production of catalase enzyme

Explanation

The waxy mycolic acids in the mycobacterial cell wall bind carbolfuchsin and resist decolorization by acid-alcohol, producing the acid-fast appearance. Catalase production and capsule presence do not explain the staining property.

Question 12Identification of Infectious Disease Processes

IgM antibody detected in a single serum sample is most useful for which purpose?

  1. Suggesting recent infection Correct answer.
  2. Documenting past immunity
  3. Measuring IgG avidity
  4. Determining vaccination status

Explanation

IgM is the first antibody class produced after exposure and generally declines over weeks to months, so its presence suggests recent or current infection. IgG is more useful for documenting past exposure or immunity.

Question 13Identification of Infectious Disease Processes

Which advantage does nucleic acid amplification testing offer over culture for viral pathogens?

  1. Detection of nonviable organisms Correct answer.
  2. Determination of antimicrobial susceptibility
  3. Lower cost per test
  4. Elimination of nucleic acid extraction

Explanation

Nucleic acid amplification detects viral nucleic acid whether or not the virus is viable, which is useful when culture is insensitive or the virus is fastidious. Culture requires viable virus and does not provide antimicrobial susceptibility for viruses.

Question 14Identification of Infectious Disease Processes

Production of beta-lactamase confers resistance to which antimicrobial class?

  1. Glycopeptides
  2. Fluoroquinolones
  3. Penicillins Correct answer.
  4. Aminoglycosides

Explanation

Beta-lactamases hydrolyze the beta-lactam ring, inactivating penicillins and related beta-lactam agents. Aminoglycosides, fluoroquinolones, and glycopeptides have different structures and targets.

Question 15Identification of Infectious Disease Processes

Which feature of a biofilm most directly limits the action of disinfectants?

  1. Extracellular matrix barrier Correct answer.
  2. Increased toxin production
  3. Enhanced motility
  4. Rapid replication rate

Explanation

The extracellular polymeric matrix of a biofilm impedes diffusion and creates a protective barrier that reduces disinfectant penetration. Rapid replication, toxin production, and motility do not directly explain reduced disinfectant efficacy.

Question 16Identification of Infectious Disease Processes

Which organism is an obligate intracellular bacterium transmitted by ticks?

  1. Borrelia burgdorferi
  2. Rickettsia rickettsii Correct answer.
  3. Legionella pneumophila
  4. Treponema pallidum

Explanation

Rickettsia rickettsii is an obligate intracellular bacterium transmitted by ticks and causes Rocky Mountain spotted fever. Borrelia and Treponema are extracellular spirochetes, and Legionella is a facultative intracellular organism.

Question 17Identification of Infectious Disease Processes

A patient develops vomiting 6 hours after eating reheated rice. Which organism is the most likely cause?

  1. Staphylococcus aureus
  2. Bacillus cereus Correct answer.
  3. Clostridium perfringens
  4. Salmonella enterica

Explanation

Bacillus cereus causes a short-incubation emetic syndrome when preformed cereulide toxin is present in reheated rice. Staphylococcus aureus also causes rapid vomiting but is more often linked to creamy foods or improper handling, while Clostridium perfringens and Salmonella have longer incubation periods.

Question 18Identification of Infectious Disease Processes

Which organism is a leading cause of catheter-related bloodstream infection because it forms biofilms on plastic surfaces?

  1. Klebsiella pneumoniae
  2. Escherichia coli
  3. Staphylococcus epidermidis Correct answer.
  4. Pseudomonas aeruginosa

Explanation

Staphylococcus epidermidis is a coagulase-negative staphylococcus that readily colonizes indwelling plastic catheters and forms biofilms, making it a common cause of catheter-related bloodstream infection. The other organisms can cause bloodstream infection but are less specifically associated with catheter biofilm formation.

Question 19Identification of Infectious Disease Processes

Which infection is transmitted to humans primarily through inhalation of infected rodent excreta?

  1. Tuberculosis
  2. Malaria
  3. Lyme disease
  4. Hantavirus infection Correct answer.

Explanation

Hantavirus infection is acquired mainly by inhaling aerosolized rodent excreta, especially from deer mice. Lyme disease is tick-borne, tuberculosis spreads person to person, and malaria is mosquito-borne.

Question 20Identification of Infectious Disease Processes

Which virus caused severe respiratory illness first identified in Saudi Arabia in 2012?

  1. MERS coronavirus Correct answer.
  2. Influenza A(H5N1)
  3. SARS coronavirus
  4. Nipah virus

Explanation

Middle East respiratory syndrome coronavirus (MERS-CoV) was first identified in Saudi Arabia in 2012 and causes severe respiratory illness. SARS coronavirus emerged earlier, in 2003, while influenza A(H5N1) and Nipah virus have different epidemiology.

Question 21Identification of Infectious Disease Processes

A patient has descending flaccid paralysis after eating home-canned vegetables. Which mechanism explains the toxin's action?

  1. Blocks postsynaptic acetylcholine receptors
  2. Increases intracellular cAMP
  3. Blocks acetylcholine release Correct answer.
  4. Destroys peripheral myelin

Explanation

Botulinum toxin cleaves SNARE proteins at the neuromuscular junction, preventing acetylcholine vesicle fusion and release, which produces descending flaccid paralysis. Postsynaptic blockade, cAMP elevation, and myelin destruction have different clinical presentations.

Question 22Identification of Infectious Disease Processes

A patient with AIDS has a CD4 count of 30 cells/µL and pneumonia; a urine antigen test is positive for a gram-negative bacillus. Which organism is most likely?

  1. Pneumocystis jirovecii
  2. Streptococcus pneumoniae
  3. Mycobacterium avium complex
  4. Legionella pneumophila Correct answer.

Explanation

Legionella pneumophila is a gram-negative bacillus, and the urine antigen test detects serogroup 1 antigen, making it the likely pathogen in this scenario. Streptococcus pneumoniae is gram-positive, Mycobacterium avium complex is acid-fast, and Pneumocystis jirovecii is a fungus.

Question 23Identification of Infectious Disease Processes

A traveler returns with cyclical fever; a blood smear shows ring forms and banana-shaped gametocytes. Which organism is responsible?

  1. Trypanosoma brucei
  2. Toxoplasma gondii
  3. Plasmodium falciparum Correct answer.
  4. Babesia microti

Explanation

Plasmodium falciparum infection classically shows ring forms and banana-shaped gametocytes on a peripheral blood smear. Babesia shows ring forms and Maltese crosses, Trypanosoma shows flagellated trypomastigotes, and Toxoplasma shows tachyzoites or cysts in tissue.

Question 24Identification of Infectious Disease Processes

Oseltamivir limits influenza virus spread by interfering with which step?

  1. Viral uncoating
  2. Viral attachment to host cells
  3. Release of virions from the cell Correct answer.
  4. Viral genome replication

Explanation

Oseltamivir inhibits influenza neuraminidase, preventing cleavage of sialic acid and release of progeny virions from infected cells. Attachment, uncoating, and genome replication are targeted by other antiviral mechanisms.

Question 25Identification of Infectious Disease Processes

Which spore-forming organism causes inhalational anthrax?

  1. Brucella melitensis
  2. Yersinia pestis
  3. Francisella tularensis
  4. Bacillus anthracis Correct answer.

Explanation

Bacillus anthracis is a gram-positive, spore-forming rod whose inhaled spores germinate in the lungs and cause inhalational anthrax. Francisella tularensis, Yersinia pestis, and Brucella melitensis are non-spore-forming organisms.

Question 26Identification of Infectious Disease Processes

A bacterium grows best when oxygen is present at a concentration of 2% to 10% but fails to grow in ambient air (approximately 21% oxygen). How is this organism classified?

  1. Aerotolerant anaerobe
  2. Obligate anaerobe
  3. Microaerophile Correct answer.
  4. Capnophile

Explanation

Oxygen-tolerance categories are defined by the oxygen level an organism requires and tolerates. Microaerophiles need oxygen for metabolism but are inhibited by the concentration found in ambient air, so they grow only in a reduced-oxygen atmosphere. Capnophiles instead require added carbon dioxide, and anaerobes either tolerate or require the absence of oxygen.

Question 27Identification of Infectious Disease Processes

A gram-negative coccobacillus isolated from sputum grows only on chocolate agar and shows heavier growth in the area immediately surrounding a streak of Staphylococcus aureus. Which requirement explains this growth pattern?

  1. Utilization of iron-containing compounds released by the staphylococcal streak
  2. Utilization of X factor (hematin) released by the agar base
  3. Utilization of V factor (NAD) released by the staphylococcal streak Correct answer.
  4. Utilization of carbon dioxide produced by the staphylococcal streak

Explanation

This is satellitism, the classic growth pattern of Haemophilus influenzae, which requires both X factor (hematin) and V factor (NAD). Chocolate agar supplies X factor, but it is deficient in available V factor, which staphylococci release as a metabolic byproduct and which then diffuses into the surrounding medium. Growth therefore concentrates near the staphylococcal streak rather than occurring evenly across the plate.

Question 28Identification of Infectious Disease Processes

A gram-negative rod isolated from a wound is oxidase-positive, does not ferment lactose, grows at 42°C, and produces a blue-green pigment that diffuses into the agar. Which organism is most likely?

  1. Burkholderia cepacia
  2. Pseudomonas aeruginosa Correct answer.
  3. Escherichia coli
  4. Stenotrophomonas maltophilia

Explanation

Pyocyanin, a blue-green phenazine pigment that diffuses into the medium, is characteristic of Pseudomonas aeruginosa, which is also oxidase-positive, a non-lactose fermenter, and capable of growth at 42°C. Those combined features separate it from the other nonfermenters and from lactose-fermenting enteric bacilli.

Question 29Surveillance and Epidemiologic Investigation

Which statement best describes the core purpose of an infection surveillance system in a hospital?

  1. To provide a complete financial audit of infection-related costs
  2. To discipline staff who fail to follow hand hygiene protocols
  3. To collect, analyze, and report infection data to guide prevention Correct answer.
  4. To replace the need for a facility-wide antimicrobial stewardship program

Explanation

Surveillance is the ongoing, systematic collection, analysis, interpretation, and dissemination of health data linked to action. Its purpose is to drive prevention efforts and evaluate interventions, not to assign blame or produce financial accounting.

Question 30Surveillance and Epidemiologic Investigation

An incidence rate measures which of the following?

  1. The number of deaths attributed to a condition in a year
  2. New cases arising in a population at risk during a defined period Correct answer.
  3. All existing cases of a condition at a single point in time
  4. The proportion of exposed persons who develop disease after contact

Explanation

Incidence quantifies new cases that develop in a defined population at risk over a specified time period. It is the measure of choice for tracking whether control measures are reducing new infections.

Question 31Surveillance and Epidemiologic Investigation

An infection that occurs at a stable, expected frequency within a defined population over time is described as:

  1. Endemic Correct answer.
  2. Epidemic
  3. Sporadic
  4. Pandemic

Explanation

Endemic refers to the constant or predictable presence of a disease within a population or geographic area. Epidemic denotes an increase above the expected baseline, pandemic denotes global spread, and sporadic denotes occasional isolated cases.

Question 32Surveillance and Epidemiologic Investigation

An epidemic curve plots the number of cases of a disease against which variable?

  1. Date or time of illness onset Correct answer.
  2. Duration of antibiotic therapy
  3. Age of the patient
  4. Geographic distance from the hospital

Explanation

The epidemic curve is a histogram of case counts by date or time of onset. Its shape helps distinguish a point-source exposure from a propagated, person-to-person outbreak.

Question 33Surveillance and Epidemiologic Investigation

Which best characterizes passive surveillance?

  1. Patients are interviewed on admission about recent exposures
  2. Trained auditors prospectively review all charts on the unit each day
  3. Reports are submitted by care providers and compiled by an agency Correct answer.
  4. Laboratory results are reviewed only after an outbreak is declared

Explanation

Passive surveillance depends on those providing care or laboratory services to report cases to a receiving agency or department. It is generally less complete than active surveillance because reporting depends on the reporter's awareness and diligence.

Question 34Surveillance and Epidemiologic Investigation

When calculating a device-associated infection rate such as CLABSI per 1,000 central line days, the denominator is:

  1. The number of bloodstream cultures drawn
  2. The total number of patient days hospital-wide
  3. The total number of central line days Correct answer.
  4. The number of patients admitted to the ICU

Explanation

Device-associated rates use device days in the denominator because device days represent the time at risk for the specific exposure. Patient days are used instead for rates that apply to the entire patient population.

Question 35Surveillance and Epidemiologic Investigation

At a hospital cafeteria, 60 of the 200 people who ate the potato salad developed gastroenteritis. The attack rate is:

  1. 3.3%
  2. 200%
  3. 30% Correct answer.
  4. 60%

Explanation

The attack rate is the number of people who became ill divided by the number of people exposed, multiplied by 100. Here 60 divided by 200 equals 0.30, or 30%.

Question 36Surveillance and Epidemiologic Investigation

A surveillance case definition for a healthcare-associated infection must include which element?

  1. The patient's insurance status and discharge destination
  2. The name of the attending physician
  3. Laboratory and clinical criteria that define a case Correct answer.
  4. The cost of the treatment course

Explanation

A case definition standardizes which events are counted by specifying clinical, laboratory, and time-place-person criteria. Without a consistent definition, rates cannot be compared over time or between facilities.

Question 37Surveillance and Epidemiologic Investigation

A patient with a central line inserted on hospital day 2 develops a laboratory-confirmed bloodstream infection on hospital day 5. Under NHSN CLABSI surveillance, the event is:

  1. Classified as a secondary bloodstream infection from another site
  2. Not counted, because the line was inserted after the patient was admitted to the hospital
  3. Reported only if a catheter tip culture grows the same organism
  4. Counted as CLABSI Correct answer.

Explanation

A central line must be in place for more than 2 calendar days, with the day of placement counted as day 1, and the laboratory-confirmed bloodstream infection must occur on or after day 3. Both conditions are met here.

Question 38Surveillance and Epidemiologic Investigation

Under NHSN criteria, surveillance for a surgical site infection following a procedure with a permanent implant continues for how long?

  1. 7 days
  2. 90 days Correct answer.
  3. 1 year
  4. 14 days

Explanation

SSI surveillance extends 90 days after procedures involving implants and 30 days for most other procedure categories. The extended window reflects the longer period during which implant-related infections may present.

Question 39Surveillance and Epidemiologic Investigation

A facility's standardized infection ratio is 0.65. The most appropriate interpretation is that the facility:

  1. Reported only 65 infections during the period
  2. Had fewer infections than predicted for its risk Correct answer.
  3. Had 65% more infections than predicted
  4. Has invalid data because an SIR must always exceed 1.0

Explanation

The SIR is the number of observed infections divided by the number predicted from a risk-adjusted national baseline. A value below 1.0 indicates fewer infections than predicted, and 0.65 represents a 35% reduction.

Question 40Surveillance and Epidemiologic Investigation

Switching from passive to active, prospective surveillance with trained reviewers is most likely to:

  1. Increase the computed infection rate by enlarging the denominator
  2. Increase case finding and thus the measured infection rate Correct answer.
  3. Decrease the number of infections detected
  4. Eliminate the need for a case definition

Explanation

Active surveillance with trained reviewers identifies infections that routine reporting misses, which raises the numerator and the measured rate. A higher rate after such a change may reflect better detection rather than worsening care.

Question 41Surveillance and Epidemiologic Investigation

A cluster of three postoperative wound infections caused by the same organism is noted in one week. Which is the most appropriate first step?

  1. Close the operating room immediately
  2. Begin a randomized controlled trial of a new preoperative skin prep
  3. Report the cluster to the news media
  4. Verify the diagnoses and confirm cases meet the case definition Correct answer.

Explanation

Outbreak investigation begins by verifying that the suspected cases truly meet an agreed case definition and that the diagnoses are correct. Only after confirmation should the team proceed to descriptive epidemiology, hypothesis generation, and control measures.

Question 42Surveillance and Epidemiologic Investigation

During an outbreak in a large hospital where most exposed patients cannot be easily enumerated, the most practical study design is:

  1. A randomized controlled trial
  2. A case-control study of infected and unaffected patients Correct answer.
  3. A prevalence survey of the entire community
  4. A cross-sectional survey of all patients discharged during the period

Explanation

When the population at risk is large or poorly defined, a case-control design compares affected patients with carefully selected unaffected patients to test exposure hypotheses efficiently. A cohort design is preferred only when the exposed population can be readily enumerated and followed.

Question 43Surveillance and Epidemiologic Investigation

In a cohort of ICU patients, CLABSI developed in 6% of patients with a central line and in 2% of patients without one, giving a relative risk of 3.0. This means:

  1. The risk in the exposed group is three percentage points higher
  2. The exposure prevented two-thirds of infections
  3. Three patients in the exposed group developed infection
  4. Exposed patients had three times the risk of the comparison group Correct answer.

Explanation

Relative risk is the ratio of incidence in the exposed group to incidence in the unexposed group. A value of 3.0 indicates the exposed group's risk is three times that of the comparison group.

Question 44Surveillance and Epidemiologic Investigation

NHSN risk adjustment of infection rates is primarily intended to:

  1. Adjust for differences in patient mix and device use Correct answer.
  2. Remove the need to collect denominator data
  3. Simplify reporting by eliminating stratification
  4. Increase the reported rates to encourage more funding

Explanation

Risk adjustment accounts for differences in patient characteristics and device utilization so that rates from different units or facilities can be compared fairly. Without it, facilities caring for sicker patients would appear to perform worse.

Question 45Surveillance and Epidemiologic Investigation

An infection preventionist recalculates CLABSI determinations from a sample of records using a second reviewer to check agreement. This activity is best described as:

  1. A cost-benefit analysis
  2. Validation of surveillance data by interrater reliability Correct answer.
  3. An outbreak investigation
  4. Syndromic surveillance using emergency department triage data

Explanation

Interrater reliability testing determines whether two reviewers applying the same case definition reach the same conclusion, which is a core method of surveillance data validation. Reliable case ascertainment is essential before rates are reported or compared.

Question 46Surveillance and Epidemiologic Investigation

How does a cluster differ from an outbreak?

  1. A cluster is any aggregation of cases, expected or not Correct answer.
  2. An outbreak is defined only by laboratory confirmation
  3. A cluster requires that cases be geographically dispersed
  4. A cluster always involves a single organism, an outbreak never does

Explanation

A cluster is simply an aggregation of cases in time or place, whether or not the number exceeds what is expected. When investigation shows the number exceeds the expected baseline, the aggregation is characterized as an outbreak.

Question 47Surveillance and Epidemiologic Investigation

For NHSN CAUTI surveillance, an indwelling urinary catheter must have been in place for how long before the infection is considered catheter-associated?

  1. At least 7 days
  2. More than 24 hours
  3. Any duration, including a single in-and-out catheterization
  4. More than 2 calendar days, with onset on or after day 3 Correct answer.

Explanation

NHSN requires the indwelling catheter to have been in place more than 2 calendar days, with the day of placement counted as day 1, and the urinary tract infection to occur on or after day 3. Shorter durations are not attributed to the catheter.

Question 48Surveillance and Epidemiologic Investigation

A hospital that markedly increases the number of blood cultures drawn may see its CLABSI rate rise. This is best explained by:

  1. A true increase in the virulence of the circulating organisms
  2. Random variation alone
  3. Surveillance (detection) bias from more intensive culturing Correct answer.
  4. A change in the denominator

Explanation

More intensive culturing detects more bloodstream infections, including organisms that would otherwise go unnoticed, and inflates the measured rate. This phenomenon is detection or surveillance bias and must be considered when interpreting trend data.

Question 49Surveillance and Epidemiologic Investigation

Crude rates show that patients on unit A had a higher infection risk than patients on unit B, but unit A patients also had far more device use. The best analytic approach is to:

  1. Adjust for device use before comparing the units Correct answer.
  2. Combine both units into one overall rate and stop the analysis
  3. Report the crude rates without further analysis
  4. Exclude unit A from the analysis

Explanation

Device use is a confounder because it is associated with both the unit of care and the risk of infection. Stratification or multivariable adjustment reveals whether the unit itself remains associated with infection after accounting for exposure.

Question 50Surveillance and Epidemiologic Investigation

On a p-chart of monthly hand hygiene compliance, a single point falls above the upper control limit. The correct interpretation is:

  1. The point signals special-cause variation worth investigating Correct answer.
  2. The data for that month should be deleted
  3. Nothing; single points never indicate a problem
  4. The chart limits were calculated incorrectly and should be discarded

Explanation

Statistical process control rules treat a point beyond a control limit as a signal of special-cause variation. The correct response is to investigate the process that produced that observation, not to alter or discard the data.