Tiêu đề 3. CONCEPT OF RISK IN PHARMACOEPIDEMIOLOGY.pdf ✅

PHARMD GURU Page 1 INTRODUCTION: RISK: Risk is the likelihood (or) the probability of experiencing some type of harm (or) losing something that one values. CHARACTERISTICS OF RISK: 1) Risk is not certain:  Risk is based on probability. Therefore, not everyone who is exposed to a risk condition (or) factor will have adverse outcome. 2) Risk is a relative concept:  Risk factors range from those that are only markers to minimally harmful situations to those that are markers of life-threatening situations.  Risk factors work together overtime to influence the likelihood of a negative outcome.  The longer the exposure to risk factors, the greater the likelihood the health problem will occur. FLOW OF RISK IN EPIDEMIOLOGY: CONCEPT OF RISK IN PHARMACOEPIDEMIOLOGY True risk Statistical consideration (Sampling, models, etc.) Measured estimated risk Pharmacoepidemiological considerations. (Bias, confounding etc.)
PHARMD GURU Page 2 RISK IN PHARMACOEPIDEMIOLOGY:  Health research involves the estimation of risk.  In the case of drug related research, it is important to understand the concept of risk.  It is the probability of developing an outcome when exposed to a drug.  A drug is approved for human use only after measuring the risks and benefits associated with it.  Pharmacists should know the magnitude and frequency of the risk involved in the drug in use.  Each drug outcome has its own risk.  It is a probability and depends on a variety of factors like age, sex, physical conditions, food habits, other diseases, other medicines, kinetics of drugs etc. MEASUREMENT OF RISK: The risk of an ADR is expressed in many ways. 1) Attributable risk. 2) Relative risk. 3) Odds ratio. 4) Time-risk relationship. 1) ATTRIBUTABLE RISK:  It is also called Rate difference or Risk difference.  Attributable risk is the “difference in rate of a condition” between an exposed population and an unexposed population.  Mostly calculated in cohort studies, where individuals are assembled on exposure status & followed over a period of time.  Then, the investigators count the occurrence of the disease.  The cohort is then subdivided by the level of exposure and the frequency of disease is compared between subgroups.  One is considered exposed & another unexposed. AR = R exposed —Rnon −exposed Where “R” is the rate of the outcome of interest (or) incidence.
PHARMD GURU Page 3 % AR = R exposed —Rnon −exposed R exposed x 100  The risk of a drug has to be assessed within the environment (or) atmosphere where it is used. Example: We cannot attribute all incidence of GI discomfort in people taking Ampicillin capsules to the drug since some may have it for reasons than the drug. 2) RELATIVE RISK:  Relative risk is also called as risk ratio.  It is the ratio of the probability of an event occurring (Ex: development of an adverse drug reaction to a drug) in an exposed group to the probability of the event occurring in non-exposed group. Relative risk = Proportion of events in experimental group proportion of events in control group  RR above 1 indicates treatment or exposure is associated with the outcome and below 1, means that the treatment is negatively associated with the outcome.  When the rate in the exposed group is equal to the rate in the comparison group RR will be equal to 1.  An RR of 2 means, the rate in the exposed group is twice that of non exposed group.  An RR of 0.5 means, the rate in the exposed persons is half that of non exposed persons. EXAMPLE: The probability of developing allergy among users of perfume was 20% and among those not using perfume 1% S.NO RISK ALLERGY STATUS PRESENT ABSENT 1. 2. PERFUME USERS PERFUME NON-USERS a c b d
PHARMD GURU Page 4 3) ODDS RATIO:  It is a measure of association between an exposure and an outcome like "relative risk".  Odds ratio in statistics and Epidemiology is commonly abbreviated as "OR".  Like "relative risk" determines probabilities, in OR odds are used. HOW TO FIND ODDS? EXAMPLE: There are two sample groups, one consisting of 100 men & other 100 women were identified from city residential area. In a dinner party, out of 100 men, 90 drank beer. While out of 100 women only 20 drank beer. ANSWER: The Odds of a man, drinking beer are 90 to 10, (or) 9:1, while the odds of a woman drinking beer are 20 to 80, (or) 1:4 = 0.25:1.  The odds ratio represents the odds of an outcome will occur, in particular exposure, compared to the odds of the outcome occurring in the absence of that exposure.  OR can be calculated by: