Statistics and Research

Statistics and Research for the FRCPath Part 1 Dr. Vijay Sharma Consultant Histopathologist and Honorary Senior Lecturer Liverpool Clinical Laboratories Royal Liverpool Hospital.

Topic 1

CLINICAL AUDIT & RESEARCH

Audit and research - similarities Both answer questions about quality of care or service.

Both can be carried out either prospectively or retrospectively retrospectively prospectively

Both involve sampling, data collection and analysis of findings.

Audit or research?

Research

Audit

What is the most effective way of treating pressure sores?

How are we treating pressure sores & how does this compare with accepted best practice?

Measure outcomes for the best treatment

The audit would measure process (are we doing the things we should do?)

To monitor the success of a treatment which is known to work

Audit and research - differences Audit

Intent

Research

“Research is concerned with discovering the right thing to do:Treatment and Audit is ensuring it isservice done right” (Smith, R. 1992, Audit & Research, BMJ, 305:905-6)

Allocation

Randomisation

Audit and research - differences

Clinical Audit and Effectiveness, Leaflet developed by Joanne Hill from an original idea by UBHT NHS Trust Clinical Audit Department. 2005

EMQ Option A Measures current service against a standard

Option B Designed and conducted to generate new knowledge

Option C Involves an intervention in use only

Answer Question Please assign the above options to describe: -Clinical audit -Research

A, C, E B, D

Option D

Option E

Designed and Addresses conducted to clearly defined produce questions, aims information to and objectives inform delivery of best care

MCQ

Question Answer Clinical audit ultimately is a Qualityimprovement improvementprocess process A. Quality B. Data collection process C. Management improvisation D.Monitoring and reporting process

Why • Improve patient care • Mandatory?

– “all healthcare professionals need to understand the principles of clinical audit, and the organisations in which they work must support them in undertaking clinical audit”

What are we trying to achieve?

Have we made things better?

Do something to make things better

Are we achieving it?

Why are we not achieving it?

Ross S, et al. Principles for best practice in clinical audit. Oxon: Radcliffe Medical Press, 2002

Ross S, et al. Principles for best practice in clinical audit. Oxon: Radcliffe Medical Press, 2002

Audit standards •

Clinical Audit is directly related to improving services against a standard that has already been set

“Standard” : •

The level of care to be achieved for any particular criterion –

(Irvine D, Irvine S. Making Sense of Audit. Oxford: Radcliffe Medical Press, 1991)

“Criterion”: •

A systematically developed statement that can be used to assess the appropriateness of specific healthcare decisions, services, and outcomes –

(Institute of Medicine, 1992)

Resources

Ross S, et al. Principles for best practice in clinical audit. Oxon: Radcliffe Medical Press, 2002

Topic 2

STATS

Statistics By chance?

Design and protocol development

Data collection

Data management

Project life span

Data analysis

Reporting results

Other terminologies Incidence

Rate at which new disease diagnosed

Prevalence

Number of people who are alive and who are known to have the disease (i.e. how widespread the disease is)

Sensitivity

Disease status

Specificity

Test result Number

Number of true positives Number of true positives + number of false negatives

of true negatives Number of true negatives + number of false positives https://en.wikipedia.org/wiki/HIV_test

Data distribution 25

Frequency

20

15

10

5

0 138 140 142 144 146 149 151 153 155 157 159 161 163 165 167 169 171 173 175 177 179 181 183 185 187 189 191 193 195

Height

Choose your test Type of data

Normal

Metric

Skewed

Categorical

Ordinal

Nominal

No staining 0 Weak staining 1 Strong staining 2

Female Male

Standard deviation

Paired/unpaired

Paired

Before vs. after treatment

Unpaired

Control population vs. test population

Your data Categorical

Metric Ordinal Unpaired

Paired

Do data have: - normal distribution - similar standard deviations

Paired

Nominal

Unpaired

Unpaired

Paired

Large number of categories?

Differences normally distributed?

no

yes

no

yes

no

Sample size

yes small

Statistical tests T-test (unpaired)

T-test (paired)

Wilcoxon signed rank test

Mann-Whitney U test

Fisher’s exact test

large

Chi-squared test

McNemar’s test

MCQ

Question Answer

If the outcome data are metric, unpaired and show normal distribution with similar standard deviations, the appropriate statistical test to use is:

A. Chi-squared test B. Mann-Whitney test C. Two-sample t test D. Fisher’s exact test E. McNemar’s test

EMQ Option A

Option B

Option C

Option D

Option E

Mann-Whitney U test

Chi-squared test

McNemar’s test

Fisher’s exact test

Two sample ttest (unpaired)

Option F

Option G

Option H

Option I

Option J

Wilcoxon signed rank test

Paired t-test

Question Answer A sample of teenagers are divided into male and female on the one hand, and based on dieting on the other. We hypothesize that the proportion of dieting individuals is higher among the women than among the men, and we want to test whether any difference of proportions that we observe is significant

EMQ Option A

Option B

Option C

Option D

Option E

Mann-Whitney U test

Chi-squared test

McNemar’s test

Fisher’s exact test

Two sample ttest (unpaired)

Option F

Option G

Option H

Option I

Option J

Wilcoxon signed rank test

Paired t-test

Question Answer Subjects are tested prior to a treatment, say for high blood pressure, and the same subjects are tested again after treatment with a blood-pressure lowering medication

EMQ Option A

Option B

Option C

Option D

Option E

Mann-Whitney U test

Chi-squared test

McNemar’s test

Fisher’s exact test

Two sample ttest (unpaired)

Option F

Option G

Option H

Option I

Option J

Wilcoxon signed rank test

Paired t-test

Question Answer The ratio of male to female students in the Science Faculty is exactly 1:1, but in the Pharmacology class over the past ten years there have been 80 females and 40 males.

Is this a significant departure from expectation?

Resources • Which test – http://www.youtube.com/watch?v=rulIUAN0U3w (Choosing which statistical test to use - statistics helpCreativeHeuristics - YouTube) – http://www.measuringusability.com/blog/what-test.php – http://www.graphpad.com/support/faqid/1790/

• Statistics – https://www.khanacademy.org/math/probability