Observational studies and routine data

Question 1

test accuracy of diagnostic test?

Answer 1

cross-sectional design

Question 2

test prognosis of disease?

Answer 2

cohort study

Question 3

test aetiology and risk factors of disease?

Answer 3

various non-randomised designs

Question 4

test population healthcare needs?

Answer 4

various, ecological studies

Question 5

test treatment efficacy?

Answer 5

RCT

Question 6

What is a descriptive study ?

Answer 6

describe distribution of factors or disease in relation to

• person (age, sex, race, marital status, lifestyle, job)
• place (variation between/within countries)
• time (variation over time and season)

Question 7

What types of data can be used for a descriptive study?

Answer 7

routine (births, deaths)
survey
performance management (Quality and Outcomes Framework for GPs)

Question 8

What is routine data?

Answer 8

= data routinely collected and recorded in ongoing systematic way without research question in mind at time of collection

Question 9

What are types of routine data?

Answer 9

• health outcome data (deaths, hospital admissions, primary care consultations, prescriptions, well being levels from national surveys)
• exposures and health determinant data (smoking, air pollution, crime stats)
• disease prevention data (screening and immunisation uptake)
• demographic data (census population counts)
• geographical data (health authority boundaries, location of GP practices)
• health service provision data (bed staff counts)
• births

Question 10

Advantages of routine data

Answer 10

cheap
already collected/available
standardised collection procedures
comprehensive (population coverage, large numbers)
wide range of recorded items

Question 11

Disadvantages of routine data

Answer 11

• may not answer the question
• not every case captured
• variable quality due to variable diagnostic fields
• validity may be variable
• disease labelling may vary over time/by area
• coding changes may create artificial increase/decreases in rates
• need careful interpretation

Question 12

Examples of heath outcome data

Answer 12

mortality
cancer
notification of infectious diseases
termination of pregnancy
congenital abnormalities
road traffic accidents

Question 13

Why are cross sectional studies important?

Answer 13

e. g. census every 10 years
- useful for care providers to allocate resources efficiently and plan effective prevention
- provide clues leading to hypotheses which can be used in analytical studies
- describe status of individuals re absence/presence of exposure and disease

However cannot distinguish between whether exposure preceded disease

Question 14

How is mortality recorded?

Answer 14

death certificates

• local registrars of births and deaths
• Office of National Statistics for coding/processing
• produced as routinely published tables (mortality stats)

Question 15

How is cancer registered?

Answer 15

• voluntary notification to local cancer registry
• also from death certificates
• used for incidence and survival information
• linked to hospital admissions and national clinical audits

Info allows identification of most common cancer types

Question 16

How are infectious diseases notified?

Answer 16

reported by doctors

incidence of disease

Question 17

What is the Quality and outcomes framework?

Answer 17

• component of General Medical Services contract for GPs from April 2004
• rewards practices for provision of quality care and helps to fund further improvements in delivery of clinical care
• collected in national database system called Quality Management Analysis System

Question 18

What is Administrative hospital admissions data?

Answer 18

UK’s way of classifying treatment

Question 19

What is a finished consultant episode?

Answer 19

the time spent under the cont care of a specific consultant

Question 20

What is admission?

Answer 20

comprises of 1+ episodes and/or transfers between hospitals

Question 21

What are the benefits of case control studies?

Answer 21

cheap
quick to conduct
investigate many exposures simultaneously
good for rare diseases

Question 22

What are the disadvantages of CCs?

Answer 22

need cases and controls to compare those who were exposed and unexposed to the risk factors suspected

selection bias of controls

subject to recall bias

uncertainty of exposure (disease time relationship)

poor for rare exposures

cannot calculate incidence rates directly as fixed number of controls in sample

Question 23

What is the principle of CCs and general procedure (3)?

Answer 23

comparing odds of exposure between cases and controls

1. select cases with disease, controls without
2. obtain information on past exposures, other factors
3. compare proportions of people exposed in cases and controls

Question 24

How are controls selected in case control studies?

Answer 24

control must be free of disease (outcome of interest) during same period of time in which cases were identified

representative of population of individuals identified as cases

Question 25

Sources of controls?

Answer 25

general population

• neighbourhood
• friends/relatives
• hospital

Question 26

What does the choice of control vary in?

Answer 26

Amount of recall bias
response rates
selection bias
cost

Question 27

What is a cohort?

Answer 27

group of people with something in common

represents outcome-free population from which cases will arise

Question 28

What are the types of cohort study ?

Answer 28

prospective - compare disease rates in exposed and unexposed groups after time

retrospective - with routine data to look at relationship between exposure and outcome

Question 29

Advantages of cohort?

Answer 29

look at multiple outcomes
follow natural disease history
good design to look at risks related to rare exposures
calculate incidence
minimise bias in estimating exposure if prospective

Question 30

Disadvantages of cohort?

Answer 30

inefficient for rare disease 
expensive
time consuming if prospective
loss to follow up introduces bias 
healthy worker/volunteer effect affects generalisability

Question 31

What is the STANDARDISED MORTALITY RATIO?

Answer 31

= rate ratio adjusted for age that shows the number of observed deaths (cases of disease), O, in a population to the expected number if the population has the same morbidity/mortality as a standard population corrected for differences in age/sex

Question 32

What does SMR allow?

Answer 32

compare population death rates as it is adjusted for age/sex

Question 33

Formula for SMR?

Answer 33

number of observed deaths/number of expected deaths if same age specific rates as standard population