Seminar 15: B, V & O ......................................................................................................................... 147
Seminar 16: B, V & O ......................................................................................................................... 154
Seminar 17: Validity, reliability and diagnostic tests ..................................................................... 162
Seminar 18: B, V & O part III ............................................................................................................. 175
Seminar 19: Systematic literature review ....................................................................................... 181
Seminar 20: Causality and causal inference .................................................................................. 183
Seminar 22: Power and choice of analysis technique, part I ........................................................ 192
Seminar 23: Literature search and meta-analysis ......................................................................... 201
Seminar 24: Power and choice of analysis technique, part II ....................................................... 212
,Seminar 01: Measures of disease frequency & study design
HOMEWORK ASSIGNMENTS
Homework assignment 1
Researchers can quantify the occurrence of disease by making use of measures of
disease frequency
(MODF), such as
- Prevalence (and variants of this MODF: point, period, and lifetime prevalence);
- Incidence (and variants of this MODF: cumulative incidence and incidence
density);
- Mortality;
- Case fatality rate (CFR)
1a. Define all these MODF. How should one calculate these measures?
Prevalence = cases of a disease in a population at a given point in time.
Prevalence = incidence x average disease duration
- Point prevalence = prevalence on a certain moment
- Period prevalence = het deel van de populatie dat de desbetreffende ziekte
heeft gehad in een bepaalde periode (totaal zieken/gemiddelde van totale
populatie aan begin en eind van periode)
- Lifetime prevalence = prevalence where is looked at if a disease has ever
been present
Incidence = new cases of a disease in a population at a given point in time.
Cumulative incidence = (number of new cases in period/total number population at
risk at T ) (x100%) GESLOTEN POPULATIE, iedereen heeft dezelfde tijd
0
• Totaal aantal nieuwe zieken in een bepaalde periode (follow-up periode) /
totaal aantal personen in de populatie ‘at risk’ aan het begin van deze periode
(t0).
- Gesloten populatie/cohort
Incidence Density = (number of new cases in period p)/(persons x time ‘at risk’)
• Totaal aantal nieuwe zieken in een bepaalde periode / totaal aantal
geobserveerde persoonsjaren at risk gedurende deze periode.
- Dynamische populatie, REKENING HOUDEN MET TIJD, dus rekenen met
persoonsjaren
Mortality = incidentie van overlijden
Mortality = total deaths/total population at T (totaal aantal sterfgevallen in een
0
bepaalde periode/totaal aantal personen in de populatie waaruit deze sterfgevallen
afkomstig zijn aan het begin van de periode)
Case fatality rate (CFR)/letaliteitspercentage = de proportie van de incidente
patiënten met een bepaalde aandoeningen die ten gevolge van die aandoening
overlijdt in een bepaalde periode (totaal aantal sterfgevallen door een bepaalde
ziekte/totaal aantal incidente patiënten met deze ziekte)
• kan bij case series: selecteren van mensen met Syndroom van Down, en dan
meten wie van hen overlijdt als gevolg van Syndroom van Down
• mensen at risk zijn de mensen met de aandoening
1b. In which of the following designs can these MODF be calculated?
- Case series
, - Ecological study
- Crosssectional study/ survey
- Case-control study
- Prospective cohort study
- Retrospective (or ‘historic’) cohort study
- Randomized controlled trial (RCT)
Prevalence Incidence Mortality CFR
Point- Period- Lifetime- CI ID
Case series no no no no no no yes
Ecological study yes yes yes yes yes yes yes
Crosssectional yes yes yes yes no no no
study/survey
Case-control study no no no no no no no
Prospective cohort yes yes yes yes yes yes yes
study
Retrospective cohort yes yes yes yes yes yes yes
study
RCT yes yes yes yes yes yes yes
Ecologisch onderzoek → je hebt alle getallen.
Cross-sectioneel → 1 moment, voor incidentie en mortaliteit en CRF moet je nieuwe
gevallen kunnen registreren.
Case-control → je volgt ze niet op, je kiest zelf de aantallen. Je volgt de
uitkomstmaat niet in de tijd.
Homework assignment 2
The following table represents the results from a follow-up study over a period of 12
months. In this study the participants are continuously monitored for disease D during
their follow-up. It is assumed that all 4 participants are at-risk as long as they are
present in the study population (indicated in yellow), except when they have the
disease (indicated in blue).
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