PDC measures are calculated through use of paid, nonreversed claims for target medications. If the drug claims dataset contains claim reversals (and paid claims that were reversed), analysts must ensure that the reversed claims are not used to calculate PDC. Claim reversals can be identified through multiple methods because there may be multiple fields in a drug claim that indicate whether it is a reversal. Many drug claims datasets have a Count field that contains a 1 for a paid claim and a -1 for a claim reversal. The dataset may also have a field called Reversal that contains a Y if the claim is a reversal claim, or an N if it is not a reversal. Reversal claims typically have a negative quantity and a negative cost.
The claim reversal (-1 in the Count field or Y in the Reversal field) may have a Claim Number that is identical to the original claim being reversed. If the Claim Number for the reversal claim is not identical to the Claim Number for the original claim, analysts can create coding logic that will identify the reversed claim as immediately preceding the claim reversal. This latter approach is not usually necessary because most drug claims datasets allow a claim reversal to be linked to an original claim.