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In general observation class domains, the collected timing of observations 

When the date/time of collection is reported in any domain, the date/time should go into the --DTC field (e.g., EGDTC for Date/Time of ECG). For any domain based on the Findings general observation class (e.g., lab tests based on a specimen), the collection date is likely to be tied to when the source of the finding was captured, not necessarily when the data were recorded. In order to ensure that the critical timing information is always represented in the same variable, the --DTC variable is used to represent the time of specimen collection. For example, in the Laboratory Test Results (LB) domain, the LBDTC variable would be used for all single-point blood collections or spot urine collections. For timed lab collections (e.g., 24-hour urine collections) the LBDTC variable would be used for the start date/time of the collection and LBENDTC for the end date/time of the collection. This approach allows the single-point and interval collections to use the same date/time variables consistently across all datasets for the Findings general observation class. The following table illustrates the proper use of these variables. Note that --STDTC should not be used in the Findings general observation class and is therefore blank in this table.

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