Add sentence in bold to Condition.onset comments Age is generally used when the patient reports an age at which the Condition began to occur. Period is generally used to convey an imprecise onset that occurred within the time period. For example, Period is not intended to convey the transition period before the chronic bronchitis or COPD condition was diagnosed, but Period can be used to convey an imprecise diagnosis date.   Range is generally used to convey an imprecise age range (e.g. 4 to 6 years old).   Because a Condition.code can represent multiple levels of granularity and can be modified over time, the onset and abatement dates can have ambiguity whether those dates apply to the current Condition.code or an earlier representation of that Condition.code. For example, if the Condition.code was initially documented as severe asthma, then it is ambiguous whether the onset and abatement dates apply to asthma (overall in that subject's lifetime) or when asthma transitioned to become severe.