Staining in days four through six of the clean days is subject to the same leniencies as staining at any time in the cycle, including attribution of a stain to an outside cause. Days one to three can indeed be more stringent regarding attribution. (Please see our article on stains (ketamim) for more details.) Blood on a bedikah within a few days of a Pap smear can usually be attributed to the procedure.
If you have the option to choose between the fourth and fifth day, then we suggest the fourth, so that you have more time between your procedure and your last bedikah on day seven. Either way, you should perform your morning bedikah before the appointment. You should skip the afternoon bedikah after the appointment, as well as the bedikot of the following day. Be sure to perform a bedikah on day seven and to ask a halachic question if there is any difficulty.
Please let us know if we can be of further assistance.
This response was updated on 10 December, 2021.