Level 2 analyses:
- Identify cohorts of interest
 - Perform more complex adjustment for confounding
 - Generate effect estimates and confidence intervals
 
Below you will find descriptions of the different types of cohort identification strategies and tools for level 2 analysis.
Type 2+: Exposures and Follow-up Time with Propensity Score Analysis
What this program does:
- Identifies exposures, follow-up time, outcomes, and covariates
 - Estimates a propensity score (based on predefined covariates and/or via a high-dimensional propensity score approach)
 - Uses matching, stratification, inverse probability of treatment weighting (IPTW), or stratum weighting for confounder adjustment and follows the analytic cohort for outcome assessment in a survival analysis framework
 
Output metrics include:
- Tables of patient characteristics (unadjusted and adjusted cohorts)
 - Measures of covariate balance
 - Distribution of propensity score by exposure group
 - Hazard ratios (with 95% confidence intervals)
 - Kaplan-Meier curves
 - IPTW/PS stratum weights
 - Attrition table
 
Continue reading about propensity score analysis on Sentinel's Git Repository.
Type 2+: Exposures and Follow-up Time with Covariate Stratification
What this program does:
- Conducts covariate stratification within each Sentinel Data Partner site via distributed programming code; returns data to the Sentinel Operations Center (SOC), aggregated, and used to calculate effect estimates
 - Groups patients in exposed and comparator cohorts into strata defined by unique values for any requester-defined combination of sex, age group, and/or year of index date
 
Continue reading about covariate stratification on Sentinel's Git Repository. 
Type 3: Self-Controlled Risk Interval Design
What this program does:
- Identifies exposure of a medical product of interest
 - Defines risk and control windows relative to the exposure date
 - Examines the occurrence of health outcomes of interest during the risk and control windows
 
Output metrics include:
- Number of exposure episodes
 - Exposed individuals
 - Individuals with a health outcome of interest in the risk and/or control windows
 - Censored individuals overall
 - Attrition table
 
Stratified by requester-defined:
- Age group
 - Sex
 - Year
 - Year-month
 - Time-to-event (in days)
 - Race (available upon request)
 - Ethnicity (available upon request)
 - Geographic region (available upon request)
 
This program provides estimates of relative risk (RR) and 95% confidence intervals.
Continue reading about self-controlled risk interval design on Sentinel's Git Repository. 
Type 4+: Medical Product Use During Pregnancy with Propensity Score Analysis
What this program does:
- Identifies exposures, follow-up time, outcomes, and covariates in a population of pregnant women
 - Estimates a propensity score (based on predefined covariates and/or via a high-dimensional propensity score approach)
 - Uses matching, stratification, inverse probability of treatment weighting (IPTW), or stratum weighting for confounder adjustment and a binary outcome assignment framework for maternal outcome assessment among the pregnant mothers or birth outcome assessment among the infants or a survival analysis framework for maternal outcomes assessment among pregnant mothers
 
Output metrics include:
- Tables of patient characteristics (unadjusted and adjusted cohorts)
 - Hazard ratios (with 95% confidence intervals)
 - IPTW/PS stratum weights
 - Measures of covariate balance
 - Distribution of propensity score by exposure group
 - Risk ratios (with 95% confidence intervals)
 - Attrition table
 
Continue reading about propensity score analysis on Sentinel's Git Repository.
Type 4+: Medical Product Use During Pregnancy with Covariate Stratification
What this program does:
- Conducts covariate stratification within each Sentinel Data Partner site via distributed programming code; returns data to the Sentinel Operations Center (SOC), aggregated, and used to calculate effect estimates
 - Groups patients in exposed and comparator cohorts into strata defined by unique values for any requester-defined combination of sex, age group, and/or year of index date
 
Continue reading about covariate stratification on Sentinel's Git Repository. 
Want more details on the functional and technical documentation of each level 2 analysis? Visit Sentinel's Git Repository.