Uncertainty & Sensitivity

Question 1

Bilcke on uncertainty

Answer 1

Scope of analysis is often limited

1. Methodological choices (time horizon/discount rate)
2. Structure uncertainty (what parameters to use?)
3. Parameter uncertainty (what value of parameter?)

Question 2

Stadhouder on uncertainty

Answer 2

Uncertainty can bias thresholds

e.g. Mortality rates; internal shifting

Question 3

Variability

Answer 3

Variation/randomness within homogenous sample of patients. Central tendency can be obtained after large number of iterations

• Standard deviations
• Microstimulation

Question 4

Heterogeneity

Answer 4

Differences between patients (Bayesian Model)

Subgroup analysis

Question 5

Dealing with uncertainty

Answer 5

1. Model discrepancy (judgements can be quantified about the difference between model output and reality)
2. Sensitivity analysis (parameter estimates across range and its impact on model results)
   Bias: Only use of complete cases when having missing values.

Question 6

Sensitivity analysis (3)

Answer 6

1. Oneway
2. Multiway
3. Threshold

Highly dependent on the researcher. Therefore can be used alongside the PSA.

Question 7

One-way analysis

Answer 7

Each parameter is varied independently.

It underestimated the overall uncertainty and correlation

Question 8

Multi-way analysis

Answer 8

More paramters at once (low-high).

Hard to find a suitable mix

Question 9

Threshold analysis

Answer 9

The critical value (above-below) depicts the conclusion of the study

Question 10

Probabilistic Sensitivy Analysis (PSA)

Answer 10

Can measure joint uncertainty across all parameters at the same time
BUT! Tend to use homogenous parameters (costs, LYs, QALYs)
- Primary data
- Secundary data
- Expert opinion

Question 11

Petrou on uncertainty

Answer 11

Dealing with:
- Skewed data: Bootstrapping
- Missing data: Multivariate regression or censoring
Set of sample stimulations, predicting value or missing full-time

Assume that WTP is known and look out for heterogeinity

Question 12

Biases (5)

Answer 12

1. Selection bias
2. Information bias
3. Attrition bias
4. Reporting/publication bias
5. Confounding bias

Question 13

Selection bias

Answer 13

Uneven dispersion of sample in population

Question 14

Information/measurement bias

Answer 14

a distortion in the measure of association caused by a lack of accurate measurements of key study variables

Question 15

Attrition bias

Answer 15

a systematic error caused by unequal loss of participants from a randomized controlled trial (RCT)

Question 16

Reporting/publication bias

Answer 16

a distortion of presented information from research due to the selective disclosure or withholding of information by parties involved with regards to the topic selected for study

Question 17

Confounding bias

Answer 17

Other factors influence outcome, by indication.
Can be reduced via comparison simular prognosis, restriction of the population or individual matching between the (non)exposed