Clinical Biostatistics 1

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Clinical Biostatistics 1
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Study Designs

• Observational studies
• Descriptive or case series
• Case-control studies (retrospective)
• Cause and incidence of disease
• Identification of risk factors
• Cross sectional studies, surveys (prevalence)
• Disease description
• Diagnosis and staging
• Disease processes, mechanisms

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Study Designs

• Observational studies
• Cohort studies (prospective)
• Causes and incidence of disease
• Natural history, prognosis
• Identification of risk factors
• Historical cohort studies

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Study Designs

• Experimental studies
• Controlled trials
• Parallel or concurrent controls
• Randomized
• Not randomized
• Sequential controls
• Self controlled
• Cross-over
• External controls (including historical)
• Studies with no controls

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Study Designs

• Meta analysis

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Case Control
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Cross sectional study
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Cohort Study Design
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Historical Cohort Study Design
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Time relationship
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Randomized Clinical Trial Design
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RCT with Crossover Design
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Trial with external control Design
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Exercise 1

• Kremer and coworkers (1987) designed a study to
  determine the efficacy of fish oil dietary
  supplements in treating rheumatoid arthritis.
  They were particularly interested in the effect
  of the fish oil on the inhibition of neutrophil
  leukotriene levels. The study involved a group of
  40 patients with class 1, 2, 3 rheumatoid
  arthritis each patient was given either a
  dietary supplement or a placebo for 14 weeks, but
  the treatment assignment was not randomized. From
  weeks 14-18, all patients took a placebo for this
  4-week-period then they were given the opposite
  treatment (dietary supplement or placebo) from
  weeks 1-14 for the next 14 weeks

crov
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Exercise 2

• A study by OMalley and Fletcher (1987) looked at
  the efficacy of the breast self examination (BSE)
  as a screening test for breast cancer by
  reviewing studies published on this topic. The
  authors found the sensitivity of BSE (the
  percentage of women with breast cancer who have a
  positive BSE) to be much lower than the
  sensitivity of a clinical breast examination or
  mammography. Although training increases the use
  of BSE and its sensitivity, the number of false
  positives (women without breast cancer who have a
  positive BSE) also increases. The authors suggest
  the need of a controlled trial on BSE before
  advocating its use as a screening device.

rvw
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Exercise 3 (part 1)

• A study of 252 adult day care providers at 6 day
  care centers and children from 3 of the centers
  was undertaken to determine the occupational risk
  of CMV infection among day care providers (Murphy
  et al 1991). This virus has been found in the
  serum of up to 80 of children at some day care
  centers and the investigators were interested in
  studying the extent of the disease among day care
  providers. All day care centers in the study
  accepted children from ages 2 weeks to 5 years.
  Each center has between 60 and 231 children at
  the time of the study. After ff up of 2.5-4.5
  years, depending on the center, the investigators
  reported an overall annual seroconversion rate of
  8 among providers.

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Exercise 3 (part 2)

• Although the rates of conversion varied a great
  deal among centers, conversion rates appeared to
  be associated with the level of CMV excretion by
  children at the centers.

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Exercise 4

• Kilbourne and colleagues (1983) investigated an
  epidemic in Spain involving multiple organ
  systems. Patients presented with cough, dyspnea,
  pleuritic chest pain, headache, fever, and
  bilateral pulmonary infiltrates. Although an
  infectious agent was first suspected, a strong
  association with cooking oil sold as olive oil
  but containing a high proportion of rapeseed oil
  was detected. Epidemiologic studies found that
  virtually all patients had ingested such oil but
  that unaffected persons had rarely done so.

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Exercise 5

• Knutson and associates (1981) treated wound,
  burn, and ulcer patients using granulated sugar
  combined with povidone iodine (PI). The study was
  undertaken from Jan 1976 to Aug 1980 during which
  time, 759 patients were treated. Of these 154
  were treated with standard therapy and the
  remaining 605 were treated with sugar and PI.
  Uniformity in treatment and judgment regarding
  the healing process were enhanced by using 3
  physician investigators to oversee the process
  and by documenting wound healing with 35 mm
  transparencies. The investigators reported that a
  much lower percentage of patients treated with
  sugar-PI required skin grafts.

nrct
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Exercise 6 (part 1)

• Colditz and colleagues (1987) reported on the
  relationship between menopause and the risk of
  coronary heart disease in women. Subjects in the
  study were selected from the Nurses Health Study
  originally completed in 1976. the study included
  120,000 married female registered nurses aged
  30-55. Colditz et al identified 116,000 of these
  women who were premenopausal or who had a known
  type of menopause and did not have a diagnosis of
  coronary heart disease at the beginning of the
  study. The investigators were interested in
  determining whether the occurrence of menopause
  alters the risk of coronary heart disease -

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Exercise (Part 2)

• specifically whether the influence of menopausal
  status is altered by the use of postmenopausal
  estrogen. The original survey provided
  information on the subjects age, parental
  history of myocardial infarction, smoking status,
  height, weight, use of oral contraceptives or
  post menopausal hormones, and history of MI or
  angina pectoris, diabetes, HPN, or high serum
  cholesterol levels. Follow up surveys were done
  in 1978, 1980, and 1982 and the data were 94.2
  complete

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Exercise 7

• Bartle and co-workers (1986) designed a study to
  examine the association between NSAID use and
  acute non-variceal bleeding in the upper GIT. The
  association between consumption of ASA and UBI
  bleeding is well established. However there is no
  information available on non-ASA NSAIDs. The
  medical records were reviewed to obtain
  medication histories of 57 consecutive patients
  with non-variceal acute UGI hemorrhage presenting
  at a medical center to compare them with 123
  sex-matched and age-matched controls. The
  investigators found that a larger proportion of
  patients than of controls had taken NSAIDs.

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Scales of measurement

• Nominal scales
• Dichotomous or binary
• Also called qualitative observations
• Also called categorical observations
• Presented as percentage or proportions
• Ordinal scales
• Ex Ca stage, Arthritis grade, Quality of life
  grade

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Scales of measurement

• Numerical scales
• Quantitative observations
• Types
• Interval or continuous
• Discrete