L9,10,11 - Drug Discovery Flashcards
How can PGx research used to test correlation?
PGx research can test genotype-phenotype association
How can PGx research test causation?
- PGx research can establish the cause-effect relationship between the genetic variation and phenotypic variation
What does a null hypothesis state?
No association between any allele and drug resistance
What size of value for X^2 support the null hypothesis?
Null: no association between any allele and drug resistance
- A small value of X^2 supports this
observed N and expected N would be similar
What is the P value for no significant association ?
P > 0.1
no presumption against the null hypothesis
What is the P value range for marginal association ?
0.05 < P < 0.1
low presumption against null hypothesis
What is the P value for significant association ?
P < 0.05
strong presumption against null hypothesis
What is the P value for very significant association ?
- P < 0.01
Does P value measure the strength of an association relationship?
No
- P can be affected by sample size: the bigger the size, the lower the P value, even under the same frequency
- P can be affected by allele frequency
How can you measure the strength of an association?
Odds ratio
- increased risk for a phenotype by carrying a specific genotype/allele compared to the patients without carrying
How do you calculate odds ratio to measure strength?
OR = odds of phenotype in an individual with / odds of phenotype in an individual without
with / without
Calculate the odds ratio for developing drug resistance (persistence) in patients carrying T allele vs patients carrying the C allele:
OR = (539/198) / (701/578) = 2.24
- Patients carrying the T allele will have 2.24 times more chance to develop drug resistance compared to the patients carrying the C allele
Explain how to interpret different odds ratio values:
- OR = 1 –> no association
- OR > 1 –> increases the risk
- OR < 1 –> decreases the risk
What does the 95% CI indicate?
95% CI is a statistical probability for OR (the standard error of OR)
over 95% of probability that the association is confident
Explain how to interpret 95% Confidence Intervals:
- If the 95% CI is greater than 1, there is a significant risk effect
- If the 95% CI contains 1, there is no statistical significance
- If the 95% CI is less than 1, there is a significant protective effect
What is the Bonferroni correction for P values?
corrected P = 0.05/N
N = total number of SNPs tested
What value do we use as a corrected GWAS P value?
5x10^-8
Do human clinical trials have negative control?
No, they often don’t have negative control due to ethical reasons
- they compare to standard of care
What is dynamic range?
upper limit and lower limit of the data set
To have reliable results what is required?
large sample size
Why do clinical studies often use median ?
- faster
- patient data may not be normally distributed
What kind of mutation did the patients with hypercholesterolemia have?
They carry a gain-of-function PCSK9 variants
What kind of mutation did the patients with super low LDL have?
- PCSK9 nonsense mutation
- Y142X
- C679X
What are the impacts of inhibiting PCSK9?
- Inhibiting PCSK9 increases available LDL receptors which allows for more LDL-C to bind –> thus decreasing LDL-C levels
PCSK9 inhibitor is monoclonal antibody