Indirect adjustment compares a study population's rates against a standard population's rates using the study group's base population. Which statement best describes this method?

• A. It compares the study population's rates against a standard population's rates.
• B. It is used only when standard rates are well established.
• C. It requires detailed age-specific rates for the study populations.
• D. It yields directly comparable SMRs.

Answer: (A)

Indirect adjustment uses the rates from a standard population and applies them to the study population’s structure to estimate how many cases would occur if the study group had the same risk as the standard. You then compare the observed number of cases in the study population to this expected number, typically via a standardized ratio. This approach directly answers how the study population’s outcomes relate to the standard, after accounting for the study group’s composition. The statement that best describes this method is that it compares the study population’s rates against a standard population’s rates. Indirect standardization does not require the study population to have detailed age-specific rates—that's a feature of direct standardization—and SMRs from indirect adjustment aren’t automatically directly comparable across studies unless the same standard is used; the method also does not depend on standard rates being “well established” in a strict sense.