The risk for a disease (or adverse event) represents the probability for the event to occur among a defined susceptible (or exposed) population. For example, the risk of a skin rash in the first week of treatment in patients receiving an antimicrobial. When risk is presented as a proportion (per 100 patients), we assume that all patients were exposed for the same length of time. In the example above, all patients were observed for 1 week. However, it is expected that the longer a patient is susceptible, or exposed, the higher is the probability for events to be observed. Incidence rates can be used to account for different lengths of times exposed when measuring risk.3
The incidence rate is a statistical measure that represents a measure of event occurrence per population, taking into account the length of time that each member of the population was observed. In technical terms, the incidence rate of an event in a population is the ratio of new events in a specified time period (numerator) divided by the patient-time exposure (which is the sum of the periods of time at risk for each of the patients) as the denominator.
An incidence rate can be interpreted in a variety of ways, for example, 1 case per 1000 patient-years exposed could be interpreted as: 1 new case observed among 1000 persons during 1 year of exposure, or 1 new case observed among 500 patients during 2 years of exposure.
How to interpret SIRs:
The confidence interval (CI) is an interval estimate with two components to it:
How to interpret CIs that are calculated around SIRs:
Additionally, it is important to note that factors such as the size of the study populations and number of events can affect how wide the confidence interval is. More narrow CIs are associated with more precise estimates.
Refers to the time after a drug or biological product has been approved by FDA.5
PML that develops a few months after stopping one disease modifying therapy (DMT) and starting a different DMT. In these cases, PML could have developed without causing symptoms while the patient was still on the previous DMT, or shortly after stopping the previous DMT.6
Confounding of adverse event reporting occurs when the assessment of association between exposure to a drug and an adverse event is distorted by the effect of one or several other variables that are also risk factors for the outcome of interest.7
Genentech data on file: December 31, 2020, post-marketing experience; March 27, 2020, clinical trials data cut-off
Genentech data on file: December 31, 2020, post-marketing experience; March 27, 2020, clinical trials data cut-off
Rothman KJ, Greenland S, Lash TL. Modern Epidemiology. 3rd ed. Philadelphia, PA: Lippincott Williams and Wilkins; 2008.
Rothman KJ, Greenland S, Lash TL. Modern Epidemiology. 3rd ed. Philadelphia, PA: Lippincott Williams and Wilkins; 2008.
New Jersey Department of Health and Senior Services. Fact Sheet: Explanation of Standardized Incidence Ratios. March 2010. Available at: https://www.state.nj.us/health/ceohs/documents/eohap/haz_sites/passaic/pompton_lakes/pompton_lakes_fs_sir.pdf.
New Jersey Department of Health and Senior Services. Fact Sheet: Explanation of Standardized Incidence Ratios. March 2010. Available at: https://www.state.nj.us/health/ceohs/documents/eohap/haz_sites/passaic/pompton_lakes/pompton_lakes_fs_sir.pdf.
US Food and Drug Administration. Postmarketing Requirements and Commitments: Reports. https://www.fda.gov/Drugs/GuidanceComplianceRegulatoryInformation/Post-marketingPhaseIVCommitments/ucm064436.htm. Accessed January 2018
US Food and Drug Administration. Postmarketing Requirements and Commitments: Reports. https://www.fda.gov/Drugs/GuidanceComplianceRegulatoryInformation/Post-marketingPhaseIVCommitments/ucm064436.htm. Accessed January 2018
Varallo FR, et al. Clin Ther. 2017;39:686–96.
Varallo FR, et al. Clin Ther. 2017;39:686–96.
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