Case Fatality Rate (CFR)

refers to the proportion of people with a particular condition who end up dying from the condition.

CFR should be distinguished from the mortality rate, which refers to the probability of dying from a particular disease in the general population

Standardized Mortality Ratio (SMR)

represents an adjusted measure of the overall mortality, and is typically used in occupational epidemiology.

Mortality is typically adjusted for age (less commonly for gender, race and other factors). The standard population is used for comparison.

• SMR = observed number of deaths/expected number of deaths

The observed number of deaths in the population of interest (eg, miners) is then divided by the expected number to obtain the SMR.

The expected number of deaths is calculated using age-specific rates of death in the standard population (eg, total US population).

The SMR is usually used in occupational studies to determine whether the observed number of deaths in a group (eg, workers) exposed to a specific risk factor (eg, vinyl chloride) exceeds what would be expected in a similar population (eg, US population) excluding the risk factor of interest.

• SMR <1 indicates that the number of observed deaths in the study group is lower than what is expected
• SMR = 1 indicates that the number of observed deaths in the study group is equal to what is expected
• SMR >1 indicates that the number of observed deaths in the study group is greater than what is expected