Cornerstones of epidemiology: Observational studies and routine data

Question 1

what is the hierarchy of study design

Answer 1

Systematic reviews and meta-analyses (highest – but can still be inadequate) • Randomised Controlled Trials • Cohort studies • Case-control studies • Ecological studies • Descriptive/cross-sectional studies • Case report/series (lowest – but can still be valuable)

Question 2

what do descriptive studies in epidemiology examine

Answer 2

the distribution of disease across various factors including population or subgroups, geographical location and time period

Question 3

what is routine data

Answer 3

Data that are routinely collected and recorded in an ongoing systematic way, often for administrative or statutory purposes and without any specific research question in mind at the time of collection

Question 4

types of routine data

Answer 4

Health outcome data, e.g. deaths, hospital admissions and primary care consultations or prescriptions, levels of well-being from national surveys • Exposures and health determinant data, e.g. smoking, air pollution, crime statistics • Disease prevention data, e.g. screening and immunisation uptake • Demographic data, e.g. census population counts • Geographical data, e.g. health authority boundaries, location of GP practices • Births • Deaths • Cancer registrations • Notifications of infectious diseases Terminations of pregnancy • Congenital anomalies • Hospital admissions • Community systems • GP consultation data • Prescriptions • Road Traffic Accidents

Question 5

what are major sources or routine data in the UK

Answer 5

2001 Census.Health Survey for England. NHS Inpatient Survey on patient experience

Question 6

what are the advantages of routine health data

Answer 6

Relatively cheap 
Already collected and available 
Standardised collection procedures 
Relatively comprehensive – population coverage, large numbers 
Wide range of recorded items 
Available for past years

Question 7

what are the disadvantages of routine health data

Answer 7

May not answer the question (no information or not enough detail) 
Incomplete ascertainment (not every case captured)  
Variable quality (e.g. variable diagnosis fields) 
Validity may be variable (i.e. do they measure what you think they measure?) 
Disease labelling may vary over time or by area 
Need careful interpretation

Question 8

define Standardized Mortality Ratio (SMR)

Answer 8

it is aratiobetween the observed number of deaths in an study population and the number of deaths would be expected (accounting for age and often sex)

Question 9

SMR =

Answer 9

No of observed death/ No. of expected death if experienced the same age specific rates as standard population

Question 10

define Age Standardised Death Rates

Answer 10

Measuring how many people die each year and why they have died is one of the most important means of assessingthe effectiveness of a country’s health system.