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Deck 1 > Epidemiology/Statistics > Flashcards

Epidemiology/Statistics Flashcards

1
Q

What are parametric tests?

A

Parametric tests assume a normal distribution of population data for the variable being tested and are used for testing variables within a population that are interval or ratio.

examples:
Pearson
t-tests
Analysis of variance (ANOVA)
f-test
z-test

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2
Q

What are non-parametric tests?

A

Non-Parametric tests can be used for data that is not normally distributed within a population or is of nominal or ordinal value.

Examples:
Chi-squared
Spearman
Mann Whitney
Wilcoxin Signed Rank
Fisher Exact Probability

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3
Q

Categorical/Nominal variable

A

mutually exclusive, but not ordered, categories (e.g. eye color)

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4
Q

Ordinal variable

A

order matters but not the difference between values (e.g. pain score)

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5
Q

Interval variable

A

difference between two values is meaningful. The difference between a temperature of 100 degrees and 90 degrees is the same difference as between 90 degrees and 80 degrees (e.g. temperature)

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6
Q

Ratio variable

A

has all the properties of an interval variable, but also has a clear definition of 0.0. When the variable equals 0.0, there is none of that variable (e.g. height/weight)

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7
Q

What are tests of correlation?

A

Pearson (parametric)
Spearman (non-parametric)

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8
Q

What is sensitivity?

A

Sensitivity is the ability of a test to correctly identify disease.
Calculation: true positives / number of people with disease

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9
Q

What is specificity?

A

Specificity is the ability of a test to correctly exclude a disease
Calculation: true negatives / number of people without disease

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10
Q

What is positive predictive value?

A

Calculation: True Positives/All positive test results

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11
Q

What is negative predictive value?

A

Calculation: True negatives / all negative test results

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12
Q

What is positive likelihood ratio?

A

LR+ = Sensitivity / (1 - Specificity)

If the ratio is more than 10, the test is useful. If the ratio is between 5 and 10, then the test is moderately useful. If the test is less than 1, the test is not useful.

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13
Q

What is negative likelihood ratio?

A

LR- = (1- Sensitivity) / Specificity

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14
Q

What is the chance of successful delivery with VBAC?

A

successful VBAC after a single c-section is 72-76%.

If a patient has had a previous successful VBAC the figure is 87-90%

The success rate is lower if any of the following are present:
Induced labour
No previous vaginal birth
Obesity (BMI >30)
Previous C-section for dystocia

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15
Q

What is absolute risk reduction?

A

ARR = AR in control - AR in experimental

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16
Q

What is relative risk?

A

Calculation: Probability of an event when exposed/Probability of event in control group

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17
Q

what is relative risk reduction?

A

Calculations: 1 - RR

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18
Q

What is the number needed to treat?

A

Calculation: 1 / Absolute risk reduction

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19
Q

What is the odds ratio?

A

Calculation: (disease present/disease absent in exposed group) / (disease present / disease absent in control group)

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20
Q

What do the OR/RR/HR values mean?

A
  • If the RR, OR, or HR = 1, or the confidence interval (CI) = 1, then there is no statistically significant difference between treatment and control groups.
  • If the RR/OR/HR >1, and the CI does not include 1, events are significantly more likely in the treatment than the control group.
  • If the RR/OR/HR <1, and the CI does not include 1, events are significantly less likely in the treatment than the control group.
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21
Q

When is the ovarian cancer peak prevalence and incidence?

A

Peak prevalence = 60-69
Peak incidence = 80+

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22
Q

What is RCT most appropriate to investigate?

A

Intervention/treatment

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23
Q

What is cross-sectional study most appropriate to investigate?

A

Diagnostic tests

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24
Q

What is a cohort study most appropriate to investigate?

A

Assessing prognosis

25
Q

How do you calculate confidence intervals?

A

Calculation of 95% CI for mean = (mean - 1.96xSEM) to (mean + 1.96xSEM)

26
Q

What is the miscarriage rate of women >45?

27
Q

What is the miscarriage rate of women 40-44?

28
Q

What is the miscarriage rate of women aged 35-39?

29
Q

What is the miscarriage rate of women aged 30-34?

30
Q

The World Health Organisation (WHO) define maternal death as

A

maternal death to have occurred during pregnancy or within 42 days of termination of pregnancy.

31
Q

What are the levels of evidence?

A

Ia - Evidence from Meta-analysis of Randomized Controlled Trials
Ib - Evidence from at least one Randomized Controlled Trial
IIa - Evidence from at least one well designed controlled trial which is not randomized
IIb - Evidence from at least one well designed experimental trial
III - Evidence from case, correlation, and comparative studies.
IV - Evidence from a panel of experts

32
Q

What factors decrease risk of ovarian cancer?

A

Oral contraceptive use
Higher Parity
Breast feeding
Hysterectomy
Tubal Ligation
Statins
SLE

33
Q

Where do most ectopic pregnancies occur?

A

Ampullary section 70-80%
Isthmus 12%
Fimbrial 5-11%
Cornual and interstitial part of the tube 2%

34
Q

What percentage of ectopics are non-tubal?

35
Q

What is the additional risk of perinatal death with VBAC?

A

2-3/10,000 additional risk of birth-related perinatal death

36
Q

The World Health Organisation define the maternal mortality ratio as

A

The maternal mortality ratio is the number of maternal deaths per 100,000 live births.

37
Q

What is the maternal mortality rate associated with ectopic pregnancy in the UK?

38
Q

Which of infection is most commonly associated with an increased risk of ectopic pregnancy?

A

Neisseria Gonorrhoea

39
Q

What is the risk of the infant developing hypoxic ischaemic encephalopathy with VBAC?

40
Q

What happens when a study’s sample size is increased?

A

Increasing sample size decreases type 2 errors and increases power of the results.
Sensitivity and specificity of the test should remain constant regardless of sample size.

41
Q

What is the additional risk the baby will have respiratory problems after VBAC compared to elective repeat C-section (ERCS)?

A

Risk 1-2% greater with ELCS.

42
Q

What is the commonest prevalence and incidence for endometrial cancer?

A

Incidence is highest at 70-74 years of age; while prevalence is highest at 60-64.

43
Q

You are carrying out analysis of a new test for DVTs and decide to plot a ROC curve. What are the axes of the curve?

A

Sensitivity vs 1-Specificity

44
Q

What is the risk of uterine rupture after C-section?

A

25/10,000 or 0.2-0.8%
or 2-8/1000

45
Q

what condition increases risk of endometrial cancer?

46
Q

WHO defines the perinatal mortality rate as

A

The number of stillbirths and deaths in the first week of life per 1000 births

47
Q

What test can be used with a continuous variable?

A

Mann-Whitney U test

48
Q

Squamous cell carcinoma accounts for approximately how many cases of vulval cancer?

49
Q

What are the steps in an audit cycle?

A
  1. selection of a topic
  2. identification of an appropriate standard
  3. data collection to assess performance against the pre-specified standard
  4. implementation of changes to improve care if necessary
  5. data collection for a second, or subsequent, time to determine whether care has improved.
50
Q

A woman has a routine cervical smear and the results show low-grade abnormality. The HPV test is positive, so she is referred for a colposcopy.

What is the chance of her being diagnosed with cervical cancer with this smear result?

A

1 in 1000.

51
Q

What is the approximate chance of a pregnant woman in the UK experiencing a stillbirth?

52
Q

What is the action of Tranexamic Acid?

A

Anti-fibrinolytic

53
Q

Most common inherited bleeding disorder?

A

von Willebrand disease

54
Q

Patient homozygous for HbSS - condition called?

A

Sickle cell disease

55
Q

A chromosome where the centromere is not central and is instead located near the end of the chromosome?

A

Afrocentric chromosomes

56
Q

Atosiban is:

A

Oxytocin antagonist

Deck 1 (12 decks)

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