Epidemiological phrasing and measures Preben AavitslandSlide 2
Contents Epidemiology Epidemiological measures Research questions Design Synthesis: address outline measureSlide 3
Definitions of the study of disease transmission "The study of disease transmission is the efficient pursuit of reasons for sickness" "The study of disease transmission is the exploration of event and determinants of wellbeing conditions and ailment in populaces and utilization of this information to control medical issues" "The study of disease transmission is the sicence of infection in populaces and variables that decide malady event" "The study of disease transmission is the investigation of ailment event "Slide 4
Research address Design MeasureSlide 5
Measure (= what we measure)Slide 6
The Measures of illness event Prevalence P Risk R Incidence rate I Measures of causal impacts Risk difference RD Risk ratio RR Incidence rate difference IRD Incidence rate ratio IRR Odds ratio ORSlide 7
Measures of ailment occurence Prevalence P - "a depiction photograph" Risk CI - "a photograph with long presentation time" (~cumulative rate, rate extent, assault rate) Case casualty CFR = danger of death Incidence rate I - "a film" (~incidence thickness) Mortality M = rate of deathSlide 8
Prevalence (P) – 1 (Prevalence extent) The extent of a populace with a specific ailment at a given point in time The likelihood that a haphazardly picked individual has the ailment P = number of unhealthy individuals at the point in time number of people in the populace P = 0 to 1, or rate, per million and so forthSlide 9
Prevalence (P) - 2 Point commonness is pervasiveness at one point in time, the genuine predominance. The fact of the matter is either a timetable point in time, or a specific occasion, for example, birth. Lifetime commonness is the extent who has had the trademark (the illness) amid their lifetime. Seroprevalence is the extent who has antibodies, stamping prior or current disease, i.e. a lifetime pervasiveness of the disease.Slide 10
Calculating pervasiveness 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 1 A B C D E F P = 2/4 = 0,5 = halfSlide 11
Risk (R) - 1 (Incidence extent, aggregate rate, assault rate) The extent of the populace who gets the infection amid a given day and age The hazard that an arbitrarily picked individual will get the illness amid the day and age R = number of new cases amid the day and age number of people in the populace R = 0 to 1, or percent, per million and so forth., however the period must be expressedSlide 12
Calculating danger Admission day 7 days after the fact A B C D E x Condition: Same follow up for all R = 2/5 = 0.4 = 40%Slide 13
Attack rate (AR) Risk amid an episode Usually communicated for the whole scourge time frame, from the first to the last case Ex: Outbreak of cholera in nation X in March 1999 Number of cases = 490 Population at hazard = 18,600 Attack rate = 2.6%Slide 14
Case-casualty (CFR) The extent of individuals with a malady who bites the dust from that ailment amid a day and age that as a rule compares to the span of the sickness. Utilized for intense maladies. The total occurrence of passings. The danger of biting the dust from an illness in a day and age (the term of the malady) CFR = number of passings from the sickness number of individuals with the ailment CFR = 0 to 1, or percent, per million and so forth., however the period must be expressedSlide 15
Problem with hazard Must settle on day and age Ideal: take after everybody for same day and age Problem with long eras Deaths to different causes Loss to catch up Example: Five year danger of HIV contamination among medication clients Solution: Incidence rateSlide 16
Incidence rate (I) – 1 ( occurrence thickness) The speed of new instances of an ailment in the populace I = number of new cases in the day and age sum of hazard period for all people I = number per time unit of hazard, e.g. per individual yearSlide 17
Incidence rate (I) - 2 The numerator is the quantity of new cases in a day and age The denominator is individual time at hazard - either the extent of the populace amidst the period (generally satisfactory) - or the entirety of the ascertained time at hazard for every one of the people in the populaceSlide 18
Calculating occurrence rate 16 17 18 19 20 21 22 23 24 25 26 Days at hazard 6.0 10.0 8.5 5.0 A B C D E x Total days at hazard 35.5 I = 2/35.5 persondays = 5,6/100 persondaysSlide 19
Mortality rate (M) The speed of new passings created by this ailment in the populace, i.e. the occurrence of death M = number of new passings of the illness in the period sum of hazard period for all people M = number per time unit of hazard, e.g. per individual yearSlide 20
Risk versus frequency rateSlide 21
Measures of causal impacts Risk distinction RR Risk proportion RR Incidence rate contrast IRD Incidence rate proportion IRR Odds proportion ORSlide 22
The accomplice concentrate uncovered unexposedSlide 23
Occurrence among uncovered ( I 1 or R 1 ) Occurrence among unexposed ( I 0 or R 0 ) The associate review uncovered unexposedSlide 24
Absolute measures of causal impacts Exposed gathering: R 1 = 0.67 Unexposed group: R 0 = 0.24 Risk contrast RD = R 1 – R 0 = 0.67 – 0.24 = 0.43 Exposed gathering: I 1 = 172/100 000 man years Unexposed group: I 0 = 12/100 000 peron-years Incidence rate diff. IRD = I 1 – I 0 = 172/100 000 – 12/100 000 = 160/100 000 man yearsSlide 25
Relative measures of causal impacts Exposed gathering: R 1 = 0.67 Unexposed group: R 0 = 0.24 Risk proportion RR = R 1/R 0 = 0.67/0.24 = 2.8 Exposed gathering: I 1 = 172/100 000 man years Unexposed group: I 0 = 12/100 000 peron-years Incidence rate ratio IRR = I 1/I 0 = 172/100 000/12/100 000 = 14.3Slide 26
Bank A Start with € 100 Invest in one year Ends with € 140 Absolute increase 140€ – 100€ = 40€ Relative increase 140€/100€ = 1.40 Bank B Start with € 1000 Invest in one year Ends with € 1150 Absolute increase 1150€ - 1000€ = 150€ Relative increase 1150€/1000€ = 1.15 Absolute or relative measuresSlide 27
Odds proportion ( OR ) Term for RR or IRR when measured for a situation control consider … more to take afterSlide 28
Classes of research inquiries 1 what number are (getting to be) infected? (event) 2 Why are some infected? (causal impacts, etiology) 3 How would we be able to tell whether somebody is sick? (diagnostics) 4 What would we be able to accomplish for the ailing? (mediation impacts) 5 How does the infected passage? (guess) 6 How can it feel to have the sickness? (quiet encounters)Slide 29
Example: HIV disease among medication clients 1 What is the rate of HIV among drugu clients? (event) 2 How much does needle sharing increment the frequency rate of HIV? (causal impacts, etiology) 3 How great is the spit test in diagnosing HIV? (diagnostics) 4 How much does needle dispersion diminish the occurrence rate of HIV? (intercession impacts) 5 How long do sedate clients with HIV live? (forecast) 6 How can it feel to be a medication client with HIV contamination? (tolerant encounters)Slide 30
Objective The target of an epidemiological review is to acquire a gauge of an epidemiological measure without irregular or precise blunder. The exploration question ought to state what we need to quantify.Slide 31
Unspecific address: "We wish to concentrate nearer at the issue of medication clients securing HIV through sharing needles for infusions." Specific address: "By what amount does needle sharing increment the hazard among medication clients of getting to be HIV contaminated?" Points to RR Make particular inquiriesSlide 32
Designs Trial Cohort think about Case-control concentrate Cross-sectional review Qualitative reviewSlide 33
Question Design MeasureSlide 34
Summary Epidemiological research is to gauge - event ( I, R, P ) or - causal impacts ( RD, RR, IRD, IRR ) Make an unmistakable research address: What would you like to quantify? The exploration address decides the outline
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