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Transcript of HSRU is funded by the Chief Scientist Office of the Scottish Executive Health Department. The author...
HSRU is funded by the Chief Scientist Office of the Scottish Executive Health Department. The author accepts full
responsibility for this talk.
Health Services Research Unit University of Aberdeen
Health Services Research Unit University of Aberdeen
Data collection (1) Data collection (1) Quantitative:Quantitative:
Structure, Process Structure, Process and Outcomeand OutcomeClare Robertson
HSRU is funded by the Chief Scientist Office of the Scottish Government Health Directorates. The author accepts full responsibility for this talk.
Health Services Research Unit
OutlineOutline
1. What to measure – structure, process, outcome
2. Studies of structure, process and outcome
3. Outcome measurements
4. Developing a new scale
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Purpose of HSRPurpose of HSR
• To provide information regarding health care delivery
‘Health services research must provide the evidence by which health services activities are judged’ Crombie IK (1996)
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Research processResearch process1. Identify the research question
eg Is keyhole surgery better than open surgery for hernia repair?
2. Decide upon research designeg randomised controlled trial
3. Choose what to measureeg recurrence of hernia
4. Decide how to measure eg physical examination at 1 year
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Health care systemHealth care system
O u tco m e (o u tp u t)
P ro cess (th ru p u t)
S tru ctu re (in p u t)
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Deciding what to measure Deciding what to measure II
• Structurethe physical features of health care
eg premises, number of staff, range and type of equipment, medical records
• Processinteraction between health professionaland patient
eg examinations, investigations, referrals, interactions
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Deciding what to measure Deciding what to measure IIII
• Intermediate (surrogate) outcomedescribes measures which may be either process or short-term outcomes which are closely related to the outcome of interest and highly predictive of iteg measuring blood pressure when evaluating treatments for stroke
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Deciding what to measure Deciding what to measure IIIIII
• Outcome changes in a patient’s current and future health status that can be attributed to antecedent
health care (the resulting changes in the health
of that patient)
eg quality of life measures, survival, cure rate
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EXAMPLE- MRSAEXAMPLE- MRSAMRSA (sometimes referred to as the superbug) methicillin-
resistant Staphylococcus aureus.MRSA infections are more difficult to treat due to the
antibiotic-resistance of the bacteria. • septicaemia (blood poisoning), • septic shock (widespread infection of the blood that
leads to a fall in blood pressure and organ failure), • severe joint problems (septic arthritis), • Bone marrow infection (osteomyelitis), • internal abscesses anywhere within the body, • inflammation of the tissues that surround the brain and
spinal cord (meningitis), • lung infection (pneumonia), and • infection of the heart lining (endocarditis).
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Example - MRSAExample - MRSA• Those in hospital are more likely to develop
MRSA infections because they often have an entry point for the bacteria to get into their body, such as a surgical wound, a catheter, or an intravenous tube.
• MRSA infections are diagnosed by testing blood, urine or a sample of tissue from the infected area for the presence of MRSA bacteria.
• MRSA is usually passed on by human contact, often from the skin of the hands.
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MRSA- preventionMRSA- prevention
• Organisation– Regular cleaning of hospitals
• Health care professionals– Handwashing -fast-acting, special
antiseptic solutions (alcohol rubs or gels) before examination of patients
– disposable gloves when they have physical contact with open wounds
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MRSA- preventionMRSA- prevention
• Patients– Keep hands and body clean – wash your hands after using the toilet
(hand wipe)– wash your hands or clean them with a
hand-wipe before and after eating• Visitors
handwashing when enter patient areas
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Structural studies of care I studies of care IWhen appropriate
– exploratory studies in new areas– ensuring minimum standard of care– structure is expected to be strongly
related to outcome
Methods– observation survey – questionnaire survey
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Structural studies of care IIStructural studies of care II
Advantages – easy to conduct– valuable when strong link between
structure and outcome
Disadvantage– link between structure and outcome is
tenuous
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Process studies of care IProcess studies of care I
When appropriate– process expected to be strongly related
to outcome (intermediate outcome)– quality of care– mechanisms- (behavioural)Methods– observation of process– self report instruments– case note review– routine data sources
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Process studies of care IIProcess studies of care II
Advantages– easy to conduct (?behavioural change) – stronger links between process and
outcome
Disadvantages– no guarantee that changes in process
will improve outcome
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Outcome studies of care IOutcome studies of care IWhen appropriate
– any evaluation
Methods– self administered outcome measure – interview administered outcome measure – case note review – routine data sources– trial report forms = web based(clinical
outcomes)
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Outcome studies of care IIOutcome studies of care IIAdvantages
– ‘gold standard’ for evaluation
Disadvantages– difficult to measure:
validityreliabilitytiming of evaluationaccessibility feasibility
– problems of attribution– valuation of costs
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Difficulties associated with Difficulties associated with outcome measurement outcome measurement
• Consider – How specific an outcome should be measured? – Whose values should be used?– When should assessment take place?– How will it be assessed?
• Subjective experience of health varies across individuals and time
What would you measure to assess the effects of the intervention on the ‘health’ of patients?
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What type of outcome?What type of outcome?
• critical events • condition/disease specific
– clinical• biomedical/biological markers• symptom
– functional– educational– economic
How general?
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What type of outcome?What type of outcome?How general? (continued)
• client group specific• general
– health profiles– health indices using indirect valuation– health indices using direct valuation
• patient satisfaction, health related knowledge and behaviour
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Examples: Condition specific Examples: Condition specific outcome measurement Ioutcome measurement I
• clinical – biomedical/biological markers
eg peak flow rate, blood pressure
– symptomseg wheeze,
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Examples: Condition specific Examples: Condition specific outcome measurement IIoutcome measurement II
• functionaleg disturbed nights in previous month
• educationaleg knowledge about asthma drugs
• economiceg time and travel to clinic
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Examples: Client group Examples: Client group specific IIspecific II
Hospital Anxiety and Depression Scale (HADS)
• anxiety– 7 items (4 point scale)
• depression
– 7 items (4 point scale)
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ExamplesExamples: GeneralGeneral outcome measurement I I
Health profile: eg SF-36 (36 items in 8 dimensions)
– General health perceptions (5 items)– Physical function (10 items)– Role limitation physical (4 items)– Role limitation emotional (3 items) – Mental health (5 items)– Pain (2 items)– Social functioning (2 items)– Energy (4 items)
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Examples: General outcome Examples: General outcome measurement IImeasurement II
Health indices – single value for the health status of
each patient surveyed– either indirect valuation or direct
valuation
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Examples: Health indices IExamples: Health indices I
Indirect valuation: • EUROQOL-5D (EQ-5D)
– 5 dimensions represented by one value• mobility• self care• usual activities• pain• anxiety
• Visual analogue scale (VAS)
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Examples: Health indices IIExamples: Health indices II
Direct valuation: enables patients to value their health status directly without reference to components of that health status
eg time trade offstandard gamblemagnitude estimate
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ExampleExample
• Compare two different “types” of knee replacement surgery in patients
• What outcomes might you be interested in?
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Developing a new scaleDeveloping a new scale
• Identify any suitable published scales• Devise new items • Select items• Avoid bias• Combine items to form a scale• Assess reliability• Assess validity
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Devising new itemsDevising new items
• Sources– literature review
– clinical observation
– expert opinion
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Devising new itemsDevising new items
• Defining responses– binary– categorical– ordinal– interval– continuous
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Selecting itemsSelecting items• Interpretability
– reading levelFlesch score
– jargonhow long have you had hypertension?
– value laden wordsdo you often go to your doctor with trivial problems?
– positive and negative wordingnot, rarely, never I rarely feel well agree/disagree
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Assessing validity I Assessing validity I • Face validity
appear to be assessing desired qualities
• Content validitysampling all relevant and important areas
• Criterion validitycorrelated with gold standard
• concurrently - new simple scale and SF36• predictive - prescribing behaviour scale
and actual prescribing
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Assessing validity IIAssessing validity II
• Construct validityscale correlated with other measures of underlying construct or measures independent of construct
time trade off and SF36time trade off and sleep patterns
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Assessing reliabilityAssessing reliability
• Influence of observers– Intra observer – Inter observer
• Test-retest reliability• Internal consistency
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Avoiding bias IAvoiding bias I• Social desirability
– unwilling to report things they see as socially unacceptable
• Acquiescent– agree with statements regardless of
what the content is– disguise intent of scale – use subtle items– random response technique
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ExampleExampleImagine you want to evaluate the implementation of a shared care scheme with guidelines for those newly diagnosed with asthma (cough and wheeze)
Usual care = see general practitioner only as per usual care
Shared care = see general practitioner and go to asthma clinic (3 monthly in 1st year/ 6 monthly yr 2 and 3) to see consultant – re use of asthma drugs, asthma controlGP given guidelines re referral and treatment
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QuestionsQuestions
What would you measure (& how & when)? Structure, process and outcome?
Consider: advantages/disadvantages
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Further readingFurther reading
• Bowling A. Research methods in health: Investigating health and health services, 2nd edition. Open University Press, 2002.
• McDowell and Newell (1995). Measuring health. A guide to rating scales and questionnaires. Oxford University Press.
• Wilkin, Hallam and Doggett (1992). Measures of need and outcome for primary health care. Oxford University Press.