Chapter 4: Surveillance and Epidemiological Investigation

1. Identify the median in the following list of numbers: 6, 2, 9, 7, 1, 4

a) 9 b) 7 c) 5 d) 4

c) 5 (sorted: 1, 2, 4, 6, 7, 9; the median is the average of 4 and 6)

2. In a study of whether OR A has a higher number of SSIs than OR B, the IP concludes the SSI rate in OR A is not equal to OR B, but in reality the two rates are equal. What type of statistical error has she committed?

a) No error has been committed b) She committed a Type I error c) She committed a Type II error d) She committed an error equal to β

b) Type I error (rejecting a true null hypothesis)

3. For which of the following procedure(s) is the surveillance period for deep incisional or organ/space SSI 90 days?

   1. Cesarean section

   2. Craniotomy

   3. Coronary artery bypass graft

   4. Laminectomy

a) 1, 2

b) 2, 3

c) 3, 4

d) 1, 4

b) 2, 3 (craniotomy and CABG are 90-day procedures)

4. An appropriate indicator to monitor process compliance would be:

a) Class 1 SSI rate b) Appropriate antibiotic dosage c) CLABSIs in the NICU d) Infections caused by multidrug-resistant organisms

b) Appropriate antibiotic dosage (a process measure; the others are outcome measures)

5. What key infection control activity is defined as the systematic, ongoing collection, management, analysis, and interpretation of data followed by dissemination to public health programs to stimulate public health action?

a) Research b) Surveillance c) Benchmarking d) Accreditation

b) Surveillance

6. An IP is reading a journal article that states the data are normally distributed. What does this mean?

a) When the data are plotted on a curve, it is skewed b) The mean is less than the median c) The skewness value is equal to 1 d) The mean, median, and mode of the data are equal

d) The mean, median, and mode of the data are equal

7. Which of the following is indicative of a superficial SSI?

a) Pain at the incision site 10 days after a breast reduction procedure; drainage is culture-positive for MSSA b) Stitch abscess cultured 14 days after surgery, positive for Enterococcus faecalis c) Purulent drainage from an episiotomy within 5 days of delivery d) Burn wound that cultures positive for Acinetobacter baumannii 10 days after debridement

a) Pain at the incision site 10 days after breast reduction with culture-positive drainage for MSSA

8. An IP is preparing the quarterly report for the Infection Control Committee. What information will be needed to calculate a CLABSI rate for the ICU?

   1. The total number of patients in the unit for the time period

   2. The total number of central line catheters for the time period

   3. The number of patients who had bloodstream infections identified

   4. The number of device days for the time period

a) 2, 3

b) 1, 3

c) 1, 2

d) 3, 4

d) 3, 4 (CLABSI rate = number of infections ÷ device days)

9. What type of rate would the IP want to calculate to give feedback to the surgeons at her facility?

a) Procedure-specific b) Provider-specific c) Unit-specific d) Device-specific

b) Provider-specific

10. The IP has been benchmarking her data to other facilities performing similar activities for a period of time. The IP should analyze the entire process to ensure that which of the following conditions are met?

    1. Standardized definitions are used consistently

    2. Overall rates are used to accurately track trends over time

    3. Adequate training of personnel to collect, store, manage, and analyze data

    4. Data are calculated using the same methodology as a nationally validated system

a) 1, 2, 3

b) 2, 3, 4

c) 1, 3, 4

d) 1, 2, 4

c) 1, 3, 4

11. The chi-square test can be used:

    1. To evaluate the effect of a variable on outcomes

    2. To analyze continuous data

    3. To calculate an odds ratio or relative risk

    4. If each cell of the table is greater than 5

a) 1, 2, 3

b) 1, 2, 4

c) 2, 3, 4

d) 1, 3, 4

d) 1, 3, 4

12. The measure of central tendency most affected by outliers is:

a) Mean b) Median c) Mode d) Range

a) Mean

13. The p value in statistical test results indicates:

a) Causation b) The probability of having committed a Type I error c) The probability of having committed a Type II error d) The probability of data being accurate and valid

b) The probability of having committed a Type I error

14. On a normally distributed data set, what percentage of values lies within three standard deviations from the mean?

a) 68.2 b) 95.5 c) 92.4 d) 99.7

d) 99.7

15. Which statistical test is used when the data are small in numbers?

a) Fisher's exact b) t test c) Chi-square d) z test

a) Fisher's exact

16. Statistical process control (SPC) charts are used for all of the following purposes EXCEPT:

a) Monitor the process of care b) Facilitate the determination of variation c) Eliminate natural variation d) Monitor outcomes

c) Eliminate natural variation

17. Seventy-five patients were admitted to the Medical-Surgical ICU: 40 on the surgical service and 35 on the medical service. Fifteen patients developed an HAI with MRSA. Nine of the patients with MRSA infection were on the surgical service. There were 230 patient days in the ICU for the surgical patients in January, and 325 patient days for medical patients. What was the incidence density of MRSA infection for patients on the surgical service?

a) 29 infections per 1,000 patient days b) 26 infections per 1,000 patient days c) 19 infections per 100 patient days d) 39 infections per 1,000 patient days

d) 39 infections per 1,000 patient days (9 ÷ 230 × 1,000 = 39.1)

18. Plague is endemic in parts of the Southwest United States. The word "endemic" means:

a) Natives are immune to plague b) An expected number of cases occurs each year in a given geographical area c) Plague has become resistant to all forms of treatment for this population d) The disease is seen in a seasonal pattern each year for this area

b) An expected number of cases occurs each year in a given geographical area

19. A pandemic differs from an epidemic in that:

a) Only one disease is involved b) It is usually vectorborne c) There is a higher mortality rate d) Several countries or continents are involved

d) Several countries or continents are involved

20. Specificity of a test for infection or disease is calculated as:

a) The number of true negatives divided by the number of positives found, times 100 b) The number of true negatives divided by the total number of persons with disease, times 100 c) The number of true positives divided by the total number of persons with disease, times 100 d) The number of true negatives divided by the total number of persons without disease, times 100

d) True negatives divided by the total number of persons without disease, times 100

21. A measure of dispersion that reflects the variability in values around the mean is called the:

a) Variance b) Standard deviation c) Range d) Bell curve

b) Standard deviation

22. In any normal distribution, the proportion of observations within two standard deviations of the mean is closest to:

a) 0.50 b) 0.68 c) 0.95 d) 0.98

c) 0.95

23. The most important feature of nonparametric tests is that they:

a) Make no assumption about variance in the populations b) Can only be used with ordinal levels of measurement c) Require a normal distribution d) Require equal population variances

a) Make no assumption about variance in the populations

24. Which of the following indicates a strong positive correlation?

a) r = 0 b) r = -0.993 c) r = 0.603 d) r = 0.45

c) r = 0.603

25. Seven employees have P. aeruginosa folliculitis, and six belong to the same health club (whirlpool suspected). The IP plans a case-control study with two controls per case. Which is the most appropriate control group?

a) Non-ill family members of the ill employees b) Non-ill hospital employees matched for age and sex c) Hospitalized patients with P. aeruginosa folliculitis matched for age and sex d) Non-ill members of the health club matched for age and sex

d) Non-ill members of the health club matched for age and sex

26. Which of the following steps are NOT included in hypothesis testing?

a) State the null and alternative hypotheses b) Set the significance level c) Eliminate outliers d) Compare the probability value to the significance level

c) Eliminate outliers

27. The range of the correlation coefficient is:

a) -1 to 0 b) 0 to 1 c) -1 to 1 d) None of the above

c) -1 to 1

28. If the index of kurtosis is -1.99, then the curve is:

a) Relatively flat b) Negatively skewed c) More peaked d) A typical bell-shaped curve or normal distribution

a) Relatively flat

29. The IP monitors all CABG patients for infections and pneumonia. The probability or likelihood of an event occurring is the:

a) Risk b) Attack rate c) Host factor d) Incidence

a) Risk

30. A table is used to illustrate data:

a) Using only one coordinate b) Arranged in rows and columns c) Using a system of coordinates d) Showing multiple complex factors at one time

b) Arranged in rows and columns

31. Calculate the mode for the following set of numbers: 2, 11, 5, 21, 3, 11, 8, 26

a) 24 b) 10.8 c) 11 d) 9.5

c) 11 (the most frequently occurring value)

32. As the sample size increases, how is the power of the study affected?

a) Power is independent of sample size b) Power is increased c) Power is decreased d) Power approaches 0

b) Power is increased

33. The term for an extraneous variable that systematically varies with the independent variable and influences the dependent variable is a:

a) Predictor variable b) Moderating variable c) Experimental variable d) Confounding variable

d) Confounding variable

34. When a normal distribution is graphed, which of the following are true?

    1. There is a continuous, symmetrical distribution in which both tails extend to infinity

    2. The mean, median, and mode are identical

    3. 68.3 percent of the area lies between the mean and 32 standard deviations

    4. The shape of the curve is determined by the mean and standard deviation

a) 1, 2, 3

b) 2, 3, 4

c) 1, 3, 4

d) 1, 2, 4

d) 1, 2, 4

35. Which of the following is NOT considered one of the criteria for causality?

a) The incidence of disease is higher in those who are exposed to the factor b) Evidence that the independent and dependent variables are related c) The association has been observed in numerous studies d) The onset of disease must precede exposure to the causal factor

d) The onset of disease must precede exposure to the causal factor (exposure must precede disease)

36. Which of the following are true about a frequency polygon?

    1. Is useful for showing two sets of data on a single graph

    2. Uses bars on the x axis

    3. Uses connecting lines and data points

    4. Depicts the percentage of the total that each data point represents

a) 1, 3

b) 1, 4

c) 3, 4

d) 2, 4

a) 1, 3

37. Targeted surveillance focuses on:

a) Tracking high-risk, high-volume procedures and potentially preventable HAIs b) Providing whole-house infection rates c) Tracking infections that are publicly reported d) Using the electronic surveillance systems to identify infections

a) Tracking high-risk, high-volume procedures and potentially preventable HAIs

38. The new IP for a long-term care facility is assessing adherence to hand hygiene policies. Which should he include when reporting his findings?

a) Hand hygiene episodes divided by the volume of soap used in the facility b) Hand hygiene episodes divided by the number of patient days times 1,000 c) Hand hygiene episodes divided by the volume of alcohol-based hand rub d) Hand hygiene episodes divided by the number of hand hygiene opportunities by ward or service

d) Hand hygiene episodes divided by the number of hand hygiene opportunities by ward or service

39. Which of the following viruses is the causative agent in Kaposi's sarcoma?

a) Herpes zoster virus b) Human herpesvirus 8 c) Epstein-Barr virus d) Human papillomavirus (HPV)

b) Human herpesvirus 8

40. A 38-year-old male with a 4-week history of cough and fever recently returned from the southwestern United States, and coccidioidomycosis is a possible diagnosis. Which is true regarding its epidemiology?

a) Coccidioides spp. are usually found at high elevations b) Coccidioides spp. are usually found in wet climates c) Up to 50 percent of people in endemic areas have been exposed to Coccidioides spores d) Coccidioides spp. are found on the surface of the soil

c) Up to 50 percent of people in endemic areas have been exposed to Coccidioides spores

41. The IP wants to know the proportion of a disease that could be prevented by eliminating the exposure in the entire study population. Which should the IP calculate?

a) Attributable fraction b) Attributable risk c) Population attributable risk percent d) Negative predictive value

c) Population attributable risk percent

42. The precision of an estimate of a relative risk depends on which of the following?

a) Generalisability b) Size of the study c) Validity of the study d) Presence of bias

b) Size of the study

43. The most common reservoir for highly pathogenic avian influenza H5N1 virus is:

a) Migratory birds b) Pigeons and doves c) Water fowl d) Domestic poultry

d) Domestic poultry

44. Indirect and direct causes of disease may form a complex network of events that determines the level of disease in a community. What is the term for this interrelation of events?

a) Applied epidemiology b) Iceberg phenomenon c) Causal web d) Dendrogram

c) Causal web

45. Which statement is true when the prevalence of a disease is very low?

a) The sensitivity of a diagnostic test is greatly increased b) The specificity of a diagnostic test is much greater c) The negative predictive value of a diagnostic test is very low d) The positive predictive value of a diagnostic test is lowered

d) The positive predictive value of a diagnostic test is lowered

46. A 30-year-old male is admitted to the medical ICU with 2 days of acute gastroenteritis symptoms, and the IP suspects norovirus. Which statement about norovirus epidemiology supports this?

a) Most norovirus outbreaks are caused by genotype GII.4 b) Severe cases of norovirus are most common in adults aged 25 to 45 c) Noroviruses are the most common cause of epidemic gastroenteritis worldwide d) Norovirus outbreaks occur most commonly in the summer months

c) Noroviruses are the most common cause of epidemic gastroenteritis worldwide

47. What is the attributable risk between the exposed and unexposed population in the following table?

Unexposed: 9 with disease, 7 with no disease Exposed: 17 with disease, 5 with no disease

a) 0.21 b) 0.56 c) 0.30 d) 0.77

a) 0.21 (exposed risk 17/22 = 0.77 minus unexposed risk 9/16 = 0.56)

48. A 40-year-old female with suspected C. difficile infection (CDI) also has possible inflammatory bowel disease (IBD). Which statement is most accurate regarding the relationship between IBD and CDI?

a) IBD is associated with increased morbidity and mortality associated with CDI b) Most patients with IBD acquire CDI in inpatient settings c) CDI generally develops more slowly after hospital admission among patients with IBD compared with patients without IBD d) IBD does not affect the risk of CDI from antibiotic exposure

a) IBD is associated with increased morbidity and mortality associated with CDI

49. Which statement about TB and airborne diseases among homeless individuals is most accurate?

a) Most TB infections among homeless individuals are reactivations of established disease b) Sputum testing detects more than 90 percent of patients with TB c) Screening for TB with chest X-ray may be the most cost-effective approach d) Directly observed therapy in the acute hospital setting is associated with the highest completion rates

c) Screening for TB with chest X-ray may be the most cost-effective approach

50. In a case-control study of obesity and C. difficile, BMI 30 or higher had 55 cases and 30 controls, and BMI less than 25 had 45 cases and 70 controls. Which odds ratio is correct?

a) 0.35 b) 2.85 c) 1.83 d) 0.55

b) 2.85 (OR = (55 × 70) ÷ (30 × 45) = 3850 ÷ 13